Merge pull request #4152 from livarcocc/bring_back_project_model_server

Adding dotnet-projectmodel-server back

src/dotnet/Program.cs

@@ -10,6 +10,7 @@ using System.Text;
 using Microsoft.DotNet.Cli.Utils;
 using Microsoft.DotNet.Configurer;
 using Microsoft.DotNet.PlatformAbstractions;
+using Microsoft.DotNet.ProjectModel.Server;
 using Microsoft.DotNet.Tools.Build;
 using Microsoft.DotNet.Tools.Compiler;
 using Microsoft.DotNet.Tools.Compiler.Csc;
@@ -45,7 +46,8 @@ namespace Microsoft.DotNet.Cli
             ["run3"] = Run3Command.Run,
             ["restore3"] = Restore3Command.Run,
             ["pack3"] = Pack3Command.Run,
-            ["migrate"] = MigrateCommand.Run
+            ["migrate"] = MigrateCommand.Run,
+            ["projectmodel-server"] = ProjectModelServerCommand.Run,
         };
 
         public static int Main(string[] args)

src/dotnet/commands/dotnet-projectmodel-server/ConnectionContext.cs

@@ -0,0 +1,62 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.Collections.Generic;
+using System.Net.Sockets;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+
+namespace Microsoft.DotNet.ProjectModel.Server
+{
+    internal class ConnectionContext
+    {
+        private readonly string _hostName;
+        private readonly ProcessingQueue _queue;
+        private readonly IDictionary<int, ProjectManager> _projects;
+
+        public ConnectionContext(Socket acceptedSocket,
+            string hostName,
+            ProtocolManager protocolManager,
+            DesignTimeWorkspace workspaceContext,
+            IDictionary<int, ProjectManager> projects)
+        {
+            _hostName = hostName;
+            _projects = projects;
+
+            _queue = new ProcessingQueue(new NetworkStream(acceptedSocket));
+            _queue.OnReceive += message =>
+            {
+                if (protocolManager.IsProtocolNegotiation(message))
+                {
+                    message.Sender = this;
+                    protocolManager.Negotiate(message);
+                }
+                else
+                {
+                    message.Sender = this;
+                    ProjectManager projectManager;
+                    if (!_projects.TryGetValue(message.ContextId, out projectManager))
+                    {
+                        projectManager = new ProjectManager(message.ContextId,
+                                                           workspaceContext,
+                                                           protocolManager);
+
+                        _projects[message.ContextId] = projectManager;
+                    }
+
+                    projectManager.OnReceive(message);
+                }
+            };
+        }
+
+        public void QueueStart()
+        {
+            _queue.Start();
+        }
+
+        public bool Transmit(Message message)
+        {
+            message.HostId = _hostName;
+            return _queue.Send(message);
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Helpers/DependencyTypeChangeFinder.cs

@@ -0,0 +1,101 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using Microsoft.DotNet.ProjectModel.Graph;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Helpers
+{
+    internal class DependencyTypeChangeFinder
+    {
+        public static IEnumerable<DiagnosticMessage> Diagnose(
+            ProjectContext context,
+            IEnumerable<string> previousSearchPaths)
+        {
+            var result = new List<DiagnosticMessage>();
+            var project = context.ProjectFile;
+            var libraries = context.LibraryManager.GetLibraries();
+
+            var updatedSearchPath = GetUpdatedSearchPaths(previousSearchPaths, project.ResolveSearchPaths());
+            var projectCandiates = GetProjectCandidates(updatedSearchPath);
+            var rootDependencies = libraries.FirstOrDefault(library => string.Equals(library.Identity.Name, project.Name))
+                                           ?.Dependencies
+                                           ?.ToDictionary(libraryRange => libraryRange.Name);
+
+            foreach (var library in libraries)
+            {
+                var diagnostic = Validate(library, projectCandiates, rootDependencies);
+                if (diagnostic != null)
+                {
+                    result.Add(diagnostic);
+                }
+            }
+
+            return result;
+        }
+
+        private static DiagnosticMessage Validate(LibraryDescription library,
+                                                  HashSet<string> projectCandidates,
+                                                  Dictionary<string, LibraryRange> rootDependencies)
+        {
+            if (!library.Resolved || projectCandidates == null)
+            {
+                return null;
+            }
+
+            var foundCandidate = projectCandidates.Contains(library.Identity.Name);
+
+            if ((library.Identity.Type == LibraryType.Project && !foundCandidate) ||
+                (library.Identity.Type == LibraryType.Package && foundCandidate))
+            {
+                library.Resolved = false;
+
+                var libraryRange = rootDependencies[library.Identity.Name];
+
+                return new DiagnosticMessage(
+                    ErrorCodes.NU1010,
+                    $"The type of dependency {library.Identity.Name} was changed.",
+                    libraryRange.SourceFilePath,
+                    DiagnosticMessageSeverity.Error,
+                    libraryRange.SourceLine,
+                    libraryRange.SourceColumn,
+                    library);
+            }
+
+            return null;
+        }
+
+        private static HashSet<string> GetProjectCandidates(IEnumerable<string> searchPaths)
+        {
+            if (searchPaths == null)
+            {
+                return null;
+            }
+
+            return new HashSet<string>(searchPaths.Where(path => Directory.Exists(path))
+                                                  .SelectMany(path => Directory.GetDirectories(path))
+                                                  .Where(path => File.Exists(Path.Combine(path, Project.FileName)))
+                                                  .Select(path => Path.GetFileName(path)));
+        }
+
+        /// <summary>
+        /// Returns the search paths if they're updated. Otherwise returns null.
+        /// </summary>
+        private static IEnumerable<string> GetUpdatedSearchPaths(IEnumerable<string> oldSearchPaths,
+                                                                 IEnumerable<string> newSearchPaths)
+        {
+            // The oldSearchPaths is null when the current project is not initialized. It is not necessary to 
+            // validate the dependency in this case.
+            if (oldSearchPaths == null)
+            {
+                return null;
+            }
+
+            if (Enumerable.SequenceEqual(oldSearchPaths, newSearchPaths))
+            {
+                return null;
+            }
+
+            return newSearchPaths;
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Helpers/JTokenExtensions.cs

@@ -0,0 +1,26 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Newtonsoft.Json.Linq;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Helpers
+{
+    public static class JTokenExtensions
+    {
+        public static string GetValue(this JToken token, string name)
+        {
+            return GetValue<string>(token, name);
+        }
+
+        public static TVal GetValue<TVal>(this JToken token, string name)
+        {
+            var value = token?[name];
+            if (value != null)
+            {
+                return value.Value<TVal>();
+            }
+
+            return default(TVal);
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Helpers/LibraryExtensions.cs

@@ -0,0 +1,21 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Microsoft.DotNet.ProjectModel.Graph;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Helpers
+{
+    public static class LibraryExtensions
+    {
+        public static string GetUniqueName(this LibraryDescription library)
+        {
+            var identity = library.Identity;
+            return identity.Type != LibraryType.ReferenceAssembly ? identity.Name : $"fx/{identity.Name}";
+        }
+
+        public static string GetUniqueName(this LibraryRange range)
+        {
+            return range.Target != LibraryType.ReferenceAssembly ? range.Name : $"fx/{range.Name}";
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Helpers/NuGetFrameworkExtensions.cs

@@ -0,0 +1,22 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Microsoft.DotNet.ProjectModel.Resolution;
+using NuGet.Frameworks;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Models
+{
+    public static class NuGetFrameworkExtensions
+    {
+        public static FrameworkData ToPayload(this NuGetFramework framework)
+        {
+            return new FrameworkData
+            {
+                ShortName = framework.GetShortFolderName(),
+                FrameworkName = framework.DotNetFrameworkName,
+                FriendlyName = FrameworkReferenceResolver.Default.GetFriendlyFrameworkName(framework),
+                RedistListPath = FrameworkReferenceResolver.Default.GetFrameworkRedistListPath(framework)
+            };
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Helpers/ProjectExtensions.cs

@@ -0,0 +1,59 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Helpers
+{
+    public static class ProjectExtensions
+    {
+        public static IEnumerable<string> ResolveSearchPaths(this Project project)
+        {
+            GlobalSettings settings;
+            return project.ResolveSearchPaths(out settings);
+        }
+
+        public static IEnumerable<string> ResolveSearchPaths(this Project project, out GlobalSettings globalSettings)
+        {
+            if (project == null)
+            {
+                throw new ArgumentNullException(nameof(project));
+            }
+
+            var searchPaths = new HashSet<string> { Directory.GetParent(project.ProjectDirectory).FullName };
+
+            globalSettings = project.ResolveGlobalSettings();
+            if (globalSettings != null)
+            {
+                foreach (var searchPath in globalSettings.ProjectSearchPaths)
+                {
+                    var path = Path.Combine(globalSettings.DirectoryPath, searchPath);
+                    searchPaths.Add(Path.GetFullPath(path));
+                }
+            }
+
+            return searchPaths;
+        }
+
+        public static GlobalSettings ResolveGlobalSettings(this Project project)
+        {
+            if (project == null)
+            {
+                throw new ArgumentNullException(nameof(project));
+            }
+
+            GlobalSettings settings;
+            var root = ProjectRootResolver.ResolveRootDirectory(project.ProjectDirectory);
+            if (GlobalSettings.TryGetGlobalSettings(root, out settings))
+            {
+                return settings;
+            }
+            else
+            {
+                return null;
+            }
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/InternalModels/ProjectContextSnapshot.cs

@@ -0,0 +1,93 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.DotNet.Cli.Compiler.Common;
+using Microsoft.DotNet.ProjectModel.Files;
+using Microsoft.DotNet.ProjectModel.Graph;
+using Microsoft.DotNet.ProjectModel.Server.Helpers;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+using NuGet.Frameworks;
+
+namespace Microsoft.DotNet.ProjectModel.Server
+{
+    internal class ProjectContextSnapshot
+    {
+        public string RootDependency { get; set; }
+        public NuGetFramework TargetFramework { get; set; }
+        public IReadOnlyList<string> SourceFiles { get; set; }
+        public CommonCompilerOptions CompilerOptions { get; set; }
+        public IReadOnlyList<ProjectReferenceDescription> ProjectReferences { get; set; }
+        public IReadOnlyList<string> FileReferences { get; set; }
+        public IReadOnlyList<DiagnosticMessage> DependencyDiagnostics { get; set; }
+        public IDictionary<string, DependencyDescription> Dependencies { get; set; }
+
+        public static ProjectContextSnapshot Create(ProjectContext context, string configuration, IEnumerable<string> previousSearchPaths)
+        {
+            var snapshot = new ProjectContextSnapshot();
+
+            var allDependencyDiagnostics = new List<DiagnosticMessage>();
+            allDependencyDiagnostics.AddRange(context.LibraryManager.GetAllDiagnostics());
+            allDependencyDiagnostics.AddRange(DependencyTypeChangeFinder.Diagnose(context, previousSearchPaths));
+
+            var diagnosticsLookup = allDependencyDiagnostics.ToLookup(d => d.Source);
+
+            var allExports = context.CreateExporter(configuration)
+                                    .GetAllExports()
+                                    .ToDictionary(export => export.Library.Identity.Name);
+
+            var allSourceFiles = new List<string>(GetSourceFiles(context, configuration));
+            var allFileReferences = new List<string>();
+            var allProjectReferences = new List<ProjectReferenceDescription>();
+            var allDependencies = new Dictionary<string, DependencyDescription>();
+
+            // All exports are returned. When the same library name have a ReferenceAssembly type export and a Package type export
+            // both will be listed as dependencies. Prefix "fx/" will be added to ReferenceAssembly type dependency.
+            foreach (var export in allExports.Values)
+            {
+                allSourceFiles.AddRange(export.SourceReferences.Select(f => f.ResolvedPath));
+                var diagnostics = diagnosticsLookup[export.Library].ToList();
+                var description = DependencyDescription.Create(export.Library, diagnostics, allExports);
+                allDependencies[description.Name] = description;
+
+                var projectReferene = ProjectReferenceDescription.Create(export.Library);
+                if (projectReferene != null && export.Library.Identity.Name != context.ProjectFile.Name)
+                {
+                    allProjectReferences.Add(projectReferene);
+                }
+                
+                if (export.Library.Identity.Type != LibraryType.Project)
+                {
+                    allFileReferences.AddRange(export.CompilationAssemblies.Select(asset => asset.ResolvedPath));
+                }
+            }
+
+            snapshot.RootDependency = context.ProjectFile.Name;
+            snapshot.TargetFramework = context.TargetFramework;
+            snapshot.SourceFiles = allSourceFiles.Distinct(StringComparer.OrdinalIgnoreCase).OrderBy(path => path).ToList();
+            snapshot.CompilerOptions = context.GetLanguageSpecificCompilerOptions(context.TargetFramework, configuration);
+            snapshot.ProjectReferences = allProjectReferences.OrderBy(reference => reference.Name).ToList();
+            snapshot.FileReferences = allFileReferences.Distinct(StringComparer.OrdinalIgnoreCase).OrderBy(path => path).ToList();
+            snapshot.DependencyDiagnostics = allDependencyDiagnostics;
+            snapshot.Dependencies = allDependencies;
+
+            return snapshot;
+        }
+
+        private static IEnumerable<string> GetSourceFiles(ProjectContext context, string configuration)
+        {
+            var compilerOptions = context.ProjectFile.GetCompilerOptions(context.TargetFramework, configuration);
+
+            if (compilerOptions.CompileInclude == null)
+            {
+                return context.ProjectFile.Files.SourceFiles;
+            }
+
+            var includeFiles = IncludeFilesResolver.GetIncludeFiles(compilerOptions.CompileInclude, "/", diagnostics: null);
+
+            return includeFiles.Select(f => f.SourcePath);
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/InternalModels/ProjectSnapshot.cs

@@ -0,0 +1,51 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.DotNet.ProjectModel.Server.Helpers;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+using NuGet.Frameworks;
+
+namespace Microsoft.DotNet.ProjectModel.Server
+{
+    internal class ProjectSnapshot
+    {
+        public Project Project { get; set; }
+        public string GlobalJsonPath { get; set; }
+        public IReadOnlyList<string> ProjectSearchPaths { get; set; }
+        public IReadOnlyList<DiagnosticMessage> ProjectDiagnostics { get; set; }
+        public ErrorMessage GlobalErrorMessage { get; set; }
+        public Dictionary<NuGetFramework, ProjectContextSnapshot> ProjectContexts { get; } = new Dictionary<NuGetFramework, ProjectContextSnapshot>();
+
+        public static ProjectSnapshot Create(string projectDirectory,
+                                             string configuration,
+                                             DesignTimeWorkspace workspaceContext,
+                                             IReadOnlyList<string> previousSearchPaths,
+                                             bool clearWorkspaceContextCache)
+        {
+            var projectContextsCollection = workspaceContext.GetProjectContextCollection(projectDirectory, clearWorkspaceContextCache);
+            if (!projectContextsCollection.ProjectContexts.Any())
+            {
+                throw new InvalidOperationException($"Unable to find project.json in '{projectDirectory}'");
+            }
+            GlobalSettings globalSettings;
+            var currentSearchPaths = projectContextsCollection.Project.ResolveSearchPaths(out globalSettings);
+
+            var snapshot = new ProjectSnapshot();
+            snapshot.Project = projectContextsCollection.Project;
+            snapshot.ProjectDiagnostics = new List<DiagnosticMessage>(projectContextsCollection.ProjectDiagnostics);
+            snapshot.ProjectSearchPaths = currentSearchPaths.ToList();
+            snapshot.GlobalJsonPath = globalSettings?.FilePath;
+
+            foreach (var projectContext in projectContextsCollection.FrameworkOnlyContexts)
+            {
+                snapshot.ProjectContexts[projectContext.TargetFramework] =
+                    ProjectContextSnapshot.Create(projectContext, configuration, previousSearchPaths);
+            }
+
+            return snapshot;
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/MessageTypes.cs

@@ -0,0 +1,27 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Microsoft.DotNet.ProjectModel.Server
+{
+    public class MessageTypes
+    {
+        // Incoming
+        public const string Initialize = nameof(Initialize);
+        public const string ChangeConfiguration = nameof(ChangeConfiguration);
+        public const string RefreshDependencies = nameof(RefreshDependencies);
+        public const string RestoreComplete = nameof(RestoreComplete);
+        public const string FilesChanged = nameof(FilesChanged);
+        public const string GetDiagnostics = nameof(GetDiagnostics);
+        public const string ProtocolVersion = nameof(ProtocolVersion);
+
+        // Outgoing
+        public const string Error = nameof(Error);
+        public const string ProjectInformation = nameof(ProjectInformation);
+        public const string Diagnostics = nameof(Diagnostics);
+        public const string DependencyDiagnostics = nameof(DependencyDiagnostics);
+        public const string Dependencies = nameof(Dependencies);
+        public const string CompilerOptions = nameof(CompilerOptions);
+        public const string References = nameof(References);
+        public const string Sources = nameof(Sources);
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Messengers/CompilerOptionsMessenger.cs

@@ -0,0 +1,42 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Messengers
+{
+    internal class CompilerOptionsMessenger : Messenger<ProjectContextSnapshot>
+    {
+        public CompilerOptionsMessenger(Action<string, object> transmit)
+            : base(MessageTypes.CompilerOptions, transmit)
+        { }
+
+        protected override bool CheckDifference(ProjectContextSnapshot local, ProjectContextSnapshot remote)
+        {
+            return remote.CompilerOptions != null &&
+                   Equals(local.CompilerOptions, remote.CompilerOptions);
+        }
+
+        protected override void SendPayload(ProjectContextSnapshot local, Action<object> send)
+        {
+            send(new CompilationOptionsMessage
+            {
+                Framework = local.TargetFramework.ToPayload(),
+                Options = local.CompilerOptions
+            });
+        }
+
+        protected override void SetValue(ProjectContextSnapshot local, ProjectContextSnapshot remote)
+        {
+            remote.CompilerOptions = local.CompilerOptions;
+        }
+
+        private class CompilationOptionsMessage
+        {
+            public FrameworkData Framework { get; set; }
+
+            public CommonCompilerOptions Options { get; set; }
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Messengers/DependenciesMessenger.cs

@@ -0,0 +1,47 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Messengers
+{
+    internal class DependenciesMessenger : Messenger<ProjectContextSnapshot>
+    {
+        public DependenciesMessenger(Action<string, object> transmit)
+            : base(MessageTypes.Dependencies, transmit)
+        { }
+
+        protected override bool CheckDifference(ProjectContextSnapshot local, ProjectContextSnapshot remote)
+        {
+            return remote.Dependencies != null &&
+                   string.Equals(local.RootDependency, remote.RootDependency) &&
+                   Equals(local.TargetFramework, remote.TargetFramework) &&
+                   Enumerable.SequenceEqual(local.Dependencies, remote.Dependencies);
+        }
+
+        protected override void SendPayload(ProjectContextSnapshot local, Action<object> send)
+        {
+            send(new DependenciesMessage
+            {
+                Framework = local.TargetFramework.ToPayload(),
+                RootDependency = local.RootDependency,
+                Dependencies = local.Dependencies
+            });
+        }
+
+        protected override void SetValue(ProjectContextSnapshot local, ProjectContextSnapshot remote)
+        {
+            remote.Dependencies = local.Dependencies;
+        }
+
+        private class DependenciesMessage
+        {
+            public FrameworkData Framework { get; set; }
+            public string RootDependency { get; set; }
+            public IDictionary<string, DependencyDescription> Dependencies { get; set; }
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Messengers/DependencyDiagnosticsMessenger.cs

@@ -0,0 +1,34 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Linq;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Messengers
+{
+    internal class DependencyDiagnosticsMessenger : Messenger<ProjectContextSnapshot>
+    {
+        public DependencyDiagnosticsMessenger(Action<string, object> transmit)
+            : base(MessageTypes.DependencyDiagnostics, transmit)
+        { }
+
+        protected override bool CheckDifference(ProjectContextSnapshot local, ProjectContextSnapshot remote)
+        {
+            return remote.DependencyDiagnostics != null &&
+                   Enumerable.SequenceEqual(local.DependencyDiagnostics, remote.DependencyDiagnostics);
+        }
+
+        protected override void SendPayload(ProjectContextSnapshot local, Action<object> send)
+        {
+            send(new DiagnosticsListMessage(
+                local.DependencyDiagnostics,
+                local.TargetFramework?.ToPayload()));
+        }
+
+        protected override void SetValue(ProjectContextSnapshot local, ProjectContextSnapshot remote)
+        {
+            remote.DependencyDiagnostics = local.DependencyDiagnostics;
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Messengers/GlobalErrorMessenger.cs

@@ -0,0 +1,43 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Messengers
+{
+    internal class GlobalErrorMessenger : Messenger<ProjectSnapshot>
+    {
+        public GlobalErrorMessenger(Action<string, object> transmit)
+            : base(MessageTypes.Error, transmit)
+        { }
+
+        protected override bool CheckDifference(ProjectSnapshot local, ProjectSnapshot remote)
+        {
+            return remote != null && Equals(local.GlobalErrorMessage, remote.GlobalErrorMessage);
+        }
+
+        protected override void SendPayload(ProjectSnapshot local, Action<object> send)
+        {
+            if (local.GlobalErrorMessage != null)
+            {
+                send(local.GlobalErrorMessage);
+            }
+            else
+            {
+                send(new ErrorMessage
+                {
+                    Message = null,
+                    Path = null,
+                    Line = -1,
+                    Column = -1
+                });
+            }
+        }
+
+        protected override void SetValue(ProjectSnapshot local, ProjectSnapshot remote)
+        {
+            remote.GlobalErrorMessage = local.GlobalErrorMessage;
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Messengers/Messenger.cs

@@ -0,0 +1,34 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Messengers
+{
+    internal abstract class Messenger<T> where T : class
+    {
+        protected readonly Action<string, object> _transmit;
+
+        public Messenger(string messageType, Action<string, object> transmit)
+        {
+            _transmit = transmit;
+
+            MessageType = messageType;
+        }
+
+        public string MessageType { get; }
+
+        public void UpdateRemote(T local, T remote)
+        {
+            if (!CheckDifference(local, remote))
+            {
+                SendPayload(local, payload => _transmit(MessageType, payload));
+                SetValue(local, remote);
+            }
+        }
+
+        protected abstract void SetValue(T local, T remote);        
+        protected abstract void SendPayload(T local, Action<object> send);
+        protected abstract bool CheckDifference(T local, T remote);
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Messengers/ProjectDiagnosticsMessenger.cs

@@ -0,0 +1,32 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Linq;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Messengers
+{
+    internal class ProjectDiagnosticsMessenger : Messenger<ProjectSnapshot>
+    {
+        public ProjectDiagnosticsMessenger(Action<string, object> transmit)
+            : base(MessageTypes.Diagnostics, transmit)
+        { }
+
+        protected override bool CheckDifference(ProjectSnapshot local, ProjectSnapshot remote)
+        {
+            return remote.ProjectDiagnostics != null &&
+                   Enumerable.SequenceEqual(local.ProjectDiagnostics, remote.ProjectDiagnostics);
+        }
+
+        protected override void SendPayload(ProjectSnapshot local, Action<object> send)
+        {
+            send(new DiagnosticsListMessage(local.ProjectDiagnostics));
+        }
+
+        protected override void SetValue(ProjectSnapshot local, ProjectSnapshot remote)
+        {
+            remote.ProjectDiagnostics = local.ProjectDiagnostics;
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Messengers/ProjectInformationMessenger.cs

@@ -0,0 +1,68 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Messengers
+{
+    internal class ProjectInformationMessenger : Messenger<ProjectSnapshot>
+    {
+        public ProjectInformationMessenger(Action<string, object> transmit)
+            : base(MessageTypes.ProjectInformation, transmit)
+        { }
+
+        protected override bool CheckDifference(ProjectSnapshot local, ProjectSnapshot remote)
+        {
+            return remote.Project != null &&
+                   string.Equals(local.Project.Name, remote.Project.Name) &&
+                   string.Equals(local.GlobalJsonPath, remote.GlobalJsonPath) &&
+                   Enumerable.SequenceEqual(local.Project.GetTargetFrameworks().Select(f => f.FrameworkName),
+                                            remote.Project.GetTargetFrameworks().Select(f => f.FrameworkName)) &&
+                   Enumerable.SequenceEqual(local.Project.GetConfigurations(), remote.Project.GetConfigurations()) &&
+                   Enumerable.SequenceEqual(local.Project.Commands, remote.Project.Commands) &&
+                   Enumerable.SequenceEqual(local.ProjectSearchPaths, remote.ProjectSearchPaths);
+        }
+
+        protected override void SendPayload(ProjectSnapshot local, Action<object> send)
+        {
+            send(new ProjectInformationMessage(local.Project, local.GlobalJsonPath, local.ProjectSearchPaths));
+        }
+
+        protected override void SetValue(ProjectSnapshot local, ProjectSnapshot remote)
+        {
+            remote.Project = local.Project;
+            remote.GlobalJsonPath = local.GlobalJsonPath;
+            remote.ProjectSearchPaths = local.ProjectSearchPaths;
+        }
+
+        private class ProjectInformationMessage
+        {
+            public ProjectInformationMessage(Project project,
+                                             string gloablJsonPath,
+                                             IReadOnlyList<string> projectSearchPaths)
+            {
+                Name = project.Name;
+                Frameworks = project.GetTargetFrameworks().Select(f => f.FrameworkName.ToPayload()).ToList();
+                Configurations = project.GetConfigurations().ToList();
+                Commands = project.Commands;
+                ProjectSearchPaths = projectSearchPaths;
+                GlobalJsonPath = gloablJsonPath;
+            }
+
+            public string Name { get; }
+
+            public IReadOnlyList<FrameworkData> Frameworks { get; }
+
+            public IReadOnlyList<string> Configurations { get; }
+
+            public IDictionary<string, string> Commands { get; }
+
+            public IReadOnlyList<string> ProjectSearchPaths { get; }
+
+            public string GlobalJsonPath { get; }
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Messengers/ReferencesMessenger.cs

@@ -0,0 +1,48 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Messengers
+{
+    internal class ReferencesMessenger : Messenger<ProjectContextSnapshot>
+    {
+        public ReferencesMessenger(Action<string, object> transmit)
+            : base(MessageTypes.References, transmit)
+        { }
+
+        protected override bool CheckDifference(ProjectContextSnapshot local, ProjectContextSnapshot remote)
+        {
+            return remote.FileReferences != null &&
+                   remote.ProjectReferences != null &&
+                   Enumerable.SequenceEqual(local.FileReferences, remote.FileReferences) &&
+                   Enumerable.SequenceEqual(local.ProjectReferences, remote.ProjectReferences);
+        }
+
+        protected override void SendPayload(ProjectContextSnapshot local, Action<object> send)
+        {
+            send(new ReferencesMessage
+            {
+                Framework = local.TargetFramework.ToPayload(),
+                ProjectReferences = local.ProjectReferences,
+                FileReferences = local.FileReferences
+            });
+        }
+
+        protected override void SetValue(ProjectContextSnapshot local, ProjectContextSnapshot remote)
+        {
+            remote.FileReferences = local.FileReferences;
+            remote.ProjectReferences = local.ProjectReferences;
+        }
+
+        private class ReferencesMessage
+        {
+            public FrameworkData Framework { get; set; }
+            public IReadOnlyList<string> FileReferences { get; set; }
+            public IReadOnlyList<ProjectReferenceDescription> ProjectReferences { get; set; }
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Messengers/SourcesMessenger.cs

@@ -0,0 +1,45 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Messengers
+{
+    internal class SourcesMessenger : Messenger<ProjectContextSnapshot>
+    {
+        public SourcesMessenger(Action<string, object> transmit)
+            : base(MessageTypes.Sources, transmit)
+        { }
+
+        protected override bool CheckDifference(ProjectContextSnapshot local, ProjectContextSnapshot remote)
+        {
+            return remote.SourceFiles != null &&
+                   Enumerable.SequenceEqual(local.SourceFiles, remote.SourceFiles);
+        }
+
+        protected override void SendPayload(ProjectContextSnapshot local, Action<object> send)
+        {
+            send(new SourcesMessage
+            {
+                Framework = local.TargetFramework.ToPayload(),
+                Files = local.SourceFiles,
+                GeneratedFiles = new Dictionary<string, string>()
+            });
+        }
+
+        protected override void SetValue(ProjectContextSnapshot local, ProjectContextSnapshot remote)
+        {
+            remote.SourceFiles = local.SourceFiles;
+        }
+
+        private class SourcesMessage
+        {
+            public FrameworkData Framework { get; set; }
+            public IReadOnlyList<string> Files { get; set; }
+            public IDictionary<string, string> GeneratedFiles { get; set; }
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Models/DependencyDescription.cs

@@ -0,0 +1,94 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.DotNet.ProjectModel.Compilation;
+using Microsoft.DotNet.ProjectModel.Graph;
+using NuGet.Versioning;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Models
+{
+    public class DependencyDescription
+    {
+        private DependencyDescription() { }
+
+        public string Name { get; private set; }
+
+        public string DisplayName { get; private set; }
+
+        public string Version { get; private set; }
+
+        public string Path { get; private set; }
+
+        public string Type { get; private set; }
+
+        public bool Resolved { get; private set; }
+
+        public IEnumerable<DependencyItem> Dependencies { get; private set; }
+
+        public IEnumerable<DiagnosticMessageView> Errors { get; private set; }
+
+        public IEnumerable<DiagnosticMessageView> Warnings { get; private set; }
+
+        public override bool Equals(object obj)
+        {
+            var other = obj as DependencyDescription;
+
+            return other != null &&
+                   Resolved == other.Resolved &&
+                   string.Equals(Name, other.Name) &&
+                   object.Equals(Version, other.Version) &&
+                   string.Equals(Path, other.Path) &&
+                   string.Equals(Type, other.Type) &&
+                   Enumerable.SequenceEqual(Dependencies, other.Dependencies) &&
+                   Enumerable.SequenceEqual(Errors, other.Errors) &&
+                   Enumerable.SequenceEqual(Warnings, other.Warnings);
+        }
+
+        public override int GetHashCode()
+        {
+            // These objects are currently POCOs and we're overriding equals
+            // so that things like Enumerable.SequenceEqual just work.
+            return base.GetHashCode();
+        }
+
+        public static DependencyDescription Create(LibraryDescription library,
+                                                   List<DiagnosticMessage> diagnostics,
+                                                   IDictionary<string, LibraryExport> exportsLookup)
+        {
+            var result = new DependencyDescription
+            {
+                Name = library.Identity.Name,
+                DisplayName = library.Identity.Name,
+                Version = (library.Identity.Version ?? new NuGetVersion("1.0.0")).ToNormalizedString(),
+                Type = library.Identity.Type.Value,
+                Resolved = library.Resolved,
+                Path = library.Path,
+                Dependencies = library.Dependencies.Select(dependency => GetDependencyItem(dependency, exportsLookup)),
+                Errors = diagnostics.Where(d => d.Severity == DiagnosticMessageSeverity.Error)
+                                    .Select(d => new DiagnosticMessageView(d)),
+                Warnings = diagnostics.Where(d => d.Severity == DiagnosticMessageSeverity.Warning)
+                                      .Select(d => new DiagnosticMessageView(d))
+            };
+
+            var msbuildLibrary = library as MSBuildProjectDescription;
+            if (msbuildLibrary != null)
+            {
+                result.Path = msbuildLibrary.MSBuildProjectPath;
+            }
+
+            return result;
+        }
+
+        private static DependencyItem GetDependencyItem(LibraryRange dependency,
+                                                        IDictionary<string, LibraryExport> exportsLookup)
+        {
+            return new DependencyItem
+            {
+                Name = dependency.Name,
+                Version = exportsLookup[dependency.Name].Library.Identity.Version?.ToNormalizedString()
+            };
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Models/DependencyItem.cs

@@ -0,0 +1,27 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Microsoft.DotNet.ProjectModel.Server.Models
+{
+    public class DependencyItem
+    {
+        public string Name { get; set; }
+
+        public string Version { get; set; }
+
+        public override bool Equals(object obj)
+        {
+            var other = obj as DependencyItem;
+            return other != null &&
+                   string.Equals(Name, other.Name) &&
+                   object.Equals(Version, other.Version);
+        }
+
+        public override int GetHashCode()
+        {
+            // These objects are currently POCOs and we're overriding equals
+            // so that things like Enumerable.SequenceEqual just work.
+            return base.GetHashCode();
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Models/DiagnosticMessageGroup.cs

@@ -0,0 +1,25 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.Collections.Generic;
+using NuGet.Frameworks;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Models
+{
+    public class DiagnosticMessageGroup
+    {
+        public DiagnosticMessageGroup(IEnumerable<DiagnosticMessage> diagnostics)
+            : this(framework: null, diagnostics: diagnostics)
+        { }
+
+        public DiagnosticMessageGroup(NuGetFramework framework, IEnumerable<DiagnosticMessage> diagnostics)
+        {
+            Framework = framework;
+            Diagnostics = diagnostics;
+        }
+
+        public IEnumerable<DiagnosticMessage> Diagnostics { get; }
+
+        public NuGetFramework Framework { get; }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Models/DiagnosticMessageView.cs

@@ -0,0 +1,74 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Models
+{
+    public class DiagnosticMessageView
+    {
+        public DiagnosticMessageView(DiagnosticMessage data)
+        {
+            ErrorCode = data.ErrorCode;
+            SourceFilePath = data.SourceFilePath;
+            Message = data.Message;
+            Severity = data.Severity;
+            StartLine = data.StartLine;
+            StartColumn = data.StartColumn;
+            EndLine = data.EndLine;
+            EndColumn = data.EndColumn;
+            FormattedMessage = data.FormattedMessage;
+
+            var description = data.Source as LibraryDescription;
+            if (description != null)
+            {
+                Source = new
+                {
+                    Name = description.Identity.Name,
+                    Version = description.Identity.Version?.ToString()
+                };
+            }
+        }
+
+        public string ErrorCode { get; }
+
+        public string SourceFilePath { get; }
+
+        public string Message { get; }
+
+        public DiagnosticMessageSeverity Severity { get; }
+
+        public int StartLine { get; }
+
+        public int StartColumn { get; }
+
+        public int EndLine { get; }
+
+        public int EndColumn { get; }
+
+        public string FormattedMessage { get; }
+
+        public object Source { get; }
+
+        public override bool Equals(object obj)
+        {
+            var other = obj as DiagnosticMessageView;
+
+            return other != null &&
+                   Severity == other.Severity &&
+                   StartLine == other.StartLine &&
+                   StartColumn == other.StartColumn &&
+                   EndLine == other.EndLine &&
+                   EndColumn == other.EndColumn &&
+                   string.Equals(ErrorCode, other.ErrorCode, StringComparison.Ordinal) &&
+                   string.Equals(SourceFilePath, other.SourceFilePath, StringComparison.Ordinal) &&
+                   string.Equals(Message, other.Message, StringComparison.Ordinal) &&
+                   object.Equals(Source, other.Source);
+        }
+
+        public override int GetHashCode()
+        {
+            return base.GetHashCode();
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Models/DiagnosticsListMessage.cs

@@ -0,0 +1,69 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Newtonsoft.Json;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Models
+{
+    public class DiagnosticsListMessage
+    {
+        public DiagnosticsListMessage(IEnumerable<DiagnosticMessage> diagnostics) :
+                this(diagnostics, frameworkData: null)
+        {
+        }
+
+        public DiagnosticsListMessage(IEnumerable<DiagnosticMessage> diagnostics, FrameworkData frameworkData) :
+                this(diagnostics.Select(msg => new DiagnosticMessageView(msg)).ToList(), frameworkData)
+        {
+            if (diagnostics == null)
+            {
+                throw new ArgumentNullException(nameof(diagnostics));
+            }
+        }
+
+        public DiagnosticsListMessage(IEnumerable<DiagnosticMessageView> diagnostics) :
+                this(diagnostics, frameworkData: null)
+        {
+        }
+
+        public DiagnosticsListMessage(IEnumerable<DiagnosticMessageView> diagnostics, FrameworkData frameworkData)
+        {
+            if (diagnostics == null)
+            {
+                throw new ArgumentNullException(nameof(diagnostics));
+            }
+
+            Diagnostics = diagnostics;
+            Errors = diagnostics.Where(msg => msg.Severity == DiagnosticMessageSeverity.Error).ToList();
+            Warnings = diagnostics.Where(msg => msg.Severity == DiagnosticMessageSeverity.Warning).ToList();
+            Framework = frameworkData;
+        }
+
+        public FrameworkData Framework { get; }
+
+        [JsonIgnore]
+        public IEnumerable<DiagnosticMessageView> Diagnostics { get; }
+
+        public IList<DiagnosticMessageView> Errors { get; }
+
+        public IList<DiagnosticMessageView> Warnings { get; }
+
+        public override bool Equals(object obj)
+        {
+            var other = obj as DiagnosticsListMessage;
+
+            return other != null &&
+                Enumerable.SequenceEqual(Errors, other.Errors) &&
+                Enumerable.SequenceEqual(Warnings, other.Warnings) &&
+                object.Equals(Framework, other.Framework);
+        }
+
+        public override int GetHashCode()
+        {
+            return base.GetHashCode();
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Models/ErrorMessage.cs

@@ -0,0 +1,30 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Models
+{
+    public class ErrorMessage
+    {
+        public string Message { get; set; }
+        public string Path { get; set; }
+        public int Line { get; set; }
+        public int Column { get; set; }
+
+        public override bool Equals(object obj)
+        {
+            var payload = obj as ErrorMessage;
+            return payload != null &&
+                   string.Equals(Message, payload.Message, StringComparison.Ordinal) &&
+                   string.Equals(Path, payload.Path, StringComparison.OrdinalIgnoreCase) &&
+                   Line == payload.Line &&
+                   Column == payload.Column;
+        }
+
+        public override int GetHashCode()
+        {
+            return base.GetHashCode();
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Models/FrameworkData.cs

@@ -0,0 +1,28 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Microsoft.DotNet.ProjectModel.Server.Models
+{
+    public class FrameworkData
+    {
+        public string FrameworkName { get; set; }
+        public string FriendlyName { get; set; }
+        public string ShortName { get; set; }
+        public string RedistListPath { get; set; }
+
+        public override bool Equals(object obj)
+        {
+            var other = obj as FrameworkData;
+
+            return other != null &&
+                   string.Equals(FrameworkName, other.FrameworkName);
+        }
+
+        public override int GetHashCode()
+        {
+            // These objects are currently POCOs and we're overriding equals
+            // so that things like Enumerable.SequenceEqual just work.
+            return base.GetHashCode();
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Models/Message.cs

@@ -0,0 +1,39 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace Microsoft.DotNet.ProjectModel.Server.Models
+{
+    internal class Message
+    {
+        public static Message FromPayload(string messageType, int contextId, object payload)
+        {
+            return new Message
+            {
+                MessageType = messageType,
+                ContextId = contextId,
+                Payload = payload is JToken ? (JToken)payload : JToken.FromObject(payload)
+            };
+        }
+
+        private Message() { }
+
+        public string MessageType { get; set; }
+
+        public string HostId { get; set; }
+
+        public int ContextId { get; set; } = -1;
+
+        public JToken Payload { get; set; }
+
+        [JsonIgnore]
+        public ConnectionContext Sender { get; set; }
+
+        public override string ToString()
+        {
+            return $"({HostId}, {MessageType}, {ContextId}) -> {Payload?.ToString(Formatting.Indented)}";
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Models/ProjectReferenceDescription.cs

@@ -0,0 +1,57 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Microsoft.DotNet.ProjectModel.Server.Models
+{
+    internal class ProjectReferenceDescription
+    {
+        private ProjectReferenceDescription() { }
+
+        public FrameworkData Framework { get; set; }
+        public string Name { get; set; }
+        public string Path { get; set; }
+
+        public override bool Equals(object obj)
+        {
+            var other = obj as ProjectReferenceDescription;
+            return other != null &&
+                   string.Equals(Name, other.Name) &&
+                   string.Equals(Path, other.Path);
+        }
+
+        public override int GetHashCode()
+        {
+            return base.GetHashCode();
+        }
+
+        /// <summary>
+        /// Create a ProjectReferenceDescription from given LibraryDescription. If the library doesn't 
+        /// represent a project reference returns null.
+        /// </summary>
+        public static ProjectReferenceDescription Create(LibraryDescription library)
+        {
+            if (library is ProjectDescription)
+            {
+                return new ProjectReferenceDescription
+                {
+                    Framework = library.Framework.ToPayload(),
+                    Name = library.Identity.Name,
+                    Path = library.Path
+                };
+            }
+            else if (library is MSBuildProjectDescription)
+            {
+                return new ProjectReferenceDescription
+                {
+                    Framework = library.Framework.ToPayload(),
+                    Name = library.Identity.Name,
+                    Path = ((MSBuildProjectDescription)library).MSBuildProjectPath,
+                };
+            }
+            else
+            {
+                return null;
+            }
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/ProcessingQueue.cs

@@ -0,0 +1,88 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.IO;
+using System.Threading;
+using Microsoft.DotNet.Cli.Utils;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+using Newtonsoft.Json;
+
+namespace Microsoft.DotNet.ProjectModel.Server
+{
+    internal class ProcessingQueue
+    {
+        private readonly BinaryReader _reader;
+        private readonly BinaryWriter _writer;
+
+        public ProcessingQueue(Stream stream)
+        {
+            _reader = new BinaryReader(stream);
+            _writer = new BinaryWriter(stream);
+        }
+
+        public event Action<Message> OnReceive;
+
+        public void Start()
+        {
+            Reporter.Output.WriteLine("Start");
+            new Thread(ReceiveMessages).Start();
+        }
+
+        public bool Send(Action<BinaryWriter> writeAction)
+        {
+            lock (_writer)
+            {
+                try
+                {
+                    writeAction(_writer);
+                    return true;
+                }
+                catch (IOException ex)
+                {
+                    // swallow
+                    Reporter.Output.WriteLine($"Ignore {nameof(IOException)} during sending message: \"{ex.Message}\".");
+                }
+                catch (Exception ex)
+                {
+                    Reporter.Output.WriteLine($"Unexpected exception {ex.GetType().Name} during sending message: \"{ex.Message}\".");
+                    throw;
+                }
+            }
+
+            return false;
+        }
+
+        public bool Send(Message message)
+        {
+            return Send(_writer =>
+            {
+                Reporter.Output.WriteLine($"OnSend ({message})");
+                _writer.Write(JsonConvert.SerializeObject(message));
+            });
+        }
+
+        private void ReceiveMessages()
+        {
+            try
+            {
+                while (true)
+                {
+                    var content = _reader.ReadString();
+                    var message = JsonConvert.DeserializeObject<Message>(content);
+
+                    Reporter.Output.WriteLine($"OnReceive ({message})");
+                    OnReceive(message);
+                }
+            }
+            catch (IOException ex)
+            {
+                Reporter.Output.WriteLine($"Ignore {nameof(IOException)} during receiving messages: \"{ex}\".");
+            }
+            catch (Exception ex)
+            {
+                Reporter.Error.WriteLine($"Unexpected exception {ex.GetType().Name} during receiving messages: \"{ex}\".");
+            }
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/Program.cs

@@ -0,0 +1,161 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Net;
+using System.Net.Sockets;
+using Microsoft.DotNet.Cli.CommandLine;
+using Microsoft.DotNet.Cli.Utils;
+
+namespace Microsoft.DotNet.ProjectModel.Server
+{
+    public class ProjectModelServerCommand
+    {
+        private readonly Dictionary<int, ProjectManager> _projects;
+        private readonly DesignTimeWorkspace _workspaceContext;
+        private readonly ProtocolManager _protocolManager;
+        private readonly string _hostName;
+        private readonly int _port;
+        private Socket _listenSocket;
+
+        public ProjectModelServerCommand(int port, string hostName)
+        {
+            _port = port;
+            _hostName = hostName;
+            _protocolManager = new ProtocolManager(maxVersion: 4);
+            _workspaceContext = new DesignTimeWorkspace(ProjectReaderSettings.ReadFromEnvironment());
+            _projects = new Dictionary<int, ProjectManager>();
+        }
+
+        public static int Run(string[] args)
+        {
+            var app = new CommandLineApplication();
+            app.Name = "dotnet-projectmodel-server";
+            app.Description = ".NET Project Model Server";
+            app.FullName = ".NET Design Time Server";
+            app.Description = ".NET Design Time Server";
+            app.HelpOption("-?|-h|--help");
+
+            var verbose = app.Option("--verbose", "Verbose ouput", CommandOptionType.NoValue);
+            var hostpid = app.Option("--host-pid", "The process id of the host", CommandOptionType.SingleValue);
+            var hostname = app.Option("--host-name", "The name of the host", CommandOptionType.SingleValue);
+            var port = app.Option("--port", "The TCP port used for communication", CommandOptionType.SingleValue);
+
+            app.OnExecute(() =>
+            {
+                try
+                {
+                    if (!MonitorHostProcess(hostpid))
+                    {
+                        return 1;
+                    }
+
+                    var intPort = CheckPort(port);
+                    if (intPort == -1)
+                    {
+                        return 1;
+                    }
+
+                    if (!hostname.HasValue())
+                    {
+                        Reporter.Error.WriteLine($"Option \"{hostname.LongName}\" is missing.");
+                        return 1;
+                    }
+
+                    var program = new ProjectModelServerCommand(intPort, hostname.Value());
+                    program.OpenChannel();
+                }
+                catch (Exception ex)
+                {
+                    Reporter.Error.WriteLine($"Unhandled exception in server main: {ex}");
+                    throw;
+                }
+
+                return 0;
+            });
+
+            return app.Execute(args);
+        }
+
+        public void OpenChannel()
+        {
+            _listenSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
+            _listenSocket.Bind(new IPEndPoint(IPAddress.Loopback, _port));
+            _listenSocket.Listen(10);
+
+            Reporter.Output.WriteLine($"Process ID {Process.GetCurrentProcess().Id}");
+            Reporter.Output.WriteLine($"Listening on port {_port}");
+
+            while (true)
+            {
+                var acceptSocket = _listenSocket.Accept();
+                Reporter.Output.WriteLine($"Client accepted {acceptSocket.LocalEndPoint}");
+
+                var connection = new ConnectionContext(acceptSocket,
+                                                       _hostName,
+                                                       _protocolManager,
+                                                       _workspaceContext,
+                                                       _projects);
+
+                connection.QueueStart();
+            }
+        }
+
+        public void Shutdown()
+        {
+            if (_listenSocket.Connected)
+            {
+                _listenSocket.Shutdown(SocketShutdown.Both);
+            }
+        }
+
+        private static int CheckPort(CommandOption port)
+        {
+            if (!port.HasValue())
+            {
+                Reporter.Error.WriteLine($"Option \"{port.LongName}\" is missing.");
+            }
+
+            int result;
+            if (int.TryParse(port.Value(), out result))
+            {
+                return result;
+            }
+            else
+            {
+                Reporter.Error.WriteLine($"Option \"{port.LongName}\" is not a valid Int32 value.");
+                return -1;
+            }
+        }
+
+        private static bool MonitorHostProcess(CommandOption host)
+        {
+            if (!host.HasValue())
+            {
+                Console.Error.WriteLine($"Option \"{host.LongName}\" is missing.");
+                return false;
+            }
+
+            int hostPID;
+            if (int.TryParse(host.Value(), out hostPID))
+            {
+                var hostProcess = Process.GetProcessById(hostPID);
+                hostProcess.EnableRaisingEvents = true;
+                hostProcess.Exited += (s, e) =>
+                {
+                    Process.GetCurrentProcess().Kill();
+                };
+
+                Reporter.Output.WriteLine($"Server will exit when process {hostPID} exits.");
+                return true;
+            }
+            else
+            {
+                Reporter.Error.WriteLine($"Option \"{host.LongName}\" is not a valid Int32 value.");
+                return false;
+            }
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/ProjectManager.cs

@@ -0,0 +1,327 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using Microsoft.DotNet.Cli.Utils;
+using Microsoft.DotNet.ProjectModel.Server.Helpers;
+using Microsoft.DotNet.ProjectModel.Server.Messengers;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+using NuGet.Frameworks;
+
+namespace Microsoft.DotNet.ProjectModel.Server
+{
+    internal class ProjectManager
+    {
+        private readonly object _processingLock = new object();
+        private readonly Queue<Message> _inbox = new Queue<Message>();
+        private readonly ProtocolManager _protocolManager;
+
+        private ConnectionContext _initializedContext;
+
+        // triggers
+        private readonly Trigger<string> _appPath = new Trigger<string>();
+        private readonly Trigger<string> _configure = new Trigger<string>();
+        private readonly Trigger<bool> _refreshDependencies = new Trigger<bool>();
+        private readonly Trigger<int> _filesChanged = new Trigger<int>();
+
+        private ProjectSnapshot _local = new ProjectSnapshot();
+        private ProjectSnapshot _remote = new ProjectSnapshot();
+
+        private readonly DesignTimeWorkspace _workspaceContext;
+        private int? _contextProtocolVersion;
+
+        private readonly List<Messenger<ProjectContextSnapshot>> _messengers;
+
+        private ProjectDiagnosticsMessenger _projectDiagnosticsMessenger;
+        private GlobalErrorMessenger _globalErrorMessenger;
+        private ProjectInformationMessenger _projectInforamtionMessenger;
+
+        public ProjectManager(
+            int contextId,
+            DesignTimeWorkspace workspaceContext,
+            ProtocolManager protocolManager)
+        {
+            Id = contextId;
+            _workspaceContext = workspaceContext;
+            _protocolManager = protocolManager;
+
+            _messengers = new List<Messenger<ProjectContextSnapshot>>
+            {
+                new ReferencesMessenger(Transmit),
+                new DependenciesMessenger(Transmit),
+                new DependencyDiagnosticsMessenger(Transmit),
+                new CompilerOptionsMessenger(Transmit),
+                new SourcesMessenger(Transmit)
+            };
+
+            _projectDiagnosticsMessenger = new ProjectDiagnosticsMessenger(Transmit);
+            _globalErrorMessenger = new GlobalErrorMessenger(Transmit);
+            _projectInforamtionMessenger = new ProjectInformationMessenger(Transmit);
+        }
+
+        public int Id { get; }
+
+        public string ProjectPath { get { return _appPath.Value; } }
+
+        public int ProtocolVersion
+        {
+            get
+            {
+                if (_contextProtocolVersion.HasValue)
+                {
+                    return _contextProtocolVersion.Value;
+                }
+                else
+                {
+                    return _protocolManager.CurrentVersion;
+                }
+            }
+        }
+
+        public void OnReceive(Message message)
+        {
+            lock (_inbox)
+            {
+                _inbox.Enqueue(message);
+            }
+
+            ThreadPool.QueueUserWorkItem(state => ((ProjectManager)state).ProcessLoop(), this);
+        }
+
+        private void Transmit(string messageType, object payload)
+        {
+            var message = Message.FromPayload(messageType, Id, payload);
+            _initializedContext.Transmit(message);
+        }
+
+        private void ProcessLoop()
+        {
+            if (!Monitor.TryEnter(_processingLock))
+            {
+                return;
+            }
+
+            try
+            {
+                lock (_inbox)
+                {
+                    if (!_inbox.Any())
+                    {
+                        return;
+                    }
+                }
+
+                DoProcessLoop();
+            }
+            catch (Exception ex)
+            {
+                Reporter.Error.WriteLine($"A unexpected exception occurred: {ex}");
+
+                var error = new ErrorMessage
+                {
+                    Message = ex.Message
+                };
+
+                var fileFormatException = ex as FileFormatException;
+                if (fileFormatException != null)
+                {
+                    error.Path = fileFormatException.Path;
+                    error.Line = fileFormatException.Line;
+                    error.Column = fileFormatException.Column;
+                }
+
+                var message = Message.FromPayload(MessageTypes.Error, Id, error);
+
+                _initializedContext.Transmit(message);
+                _remote.GlobalErrorMessage = error;
+            }
+            finally
+            {
+                Monitor.Exit(_processingLock);
+            }
+        }
+
+        private void DoProcessLoop()
+        {
+            while (true)
+            {
+                DrainInbox();
+
+                UpdateProject();
+                SendOutgingMessages();
+
+                lock (_inbox)
+                {
+                    if (_inbox.Count == 0)
+                    {
+                        return;
+                    }
+                }
+            }
+        }
+
+        private void DrainInbox()
+        {
+            Reporter.Output.WriteLine("Begin draining inbox.");
+
+            while (ProcessMessage()) { }
+
+            Reporter.Output.WriteLine("Finish draining inbox.");
+        }
+
+        private bool ProcessMessage()
+        {
+            Message message;
+
+            lock (_inbox)
+            {
+                if (!_inbox.Any())
+                {
+                    return false;
+                }
+
+                message = _inbox.Dequeue();
+                Debug.Assert(message != null);
+            }
+
+            Reporter.Output.WriteLine($"Received {message.MessageType}");
+
+            switch (message.MessageType)
+            {
+                case MessageTypes.Initialize:
+                    Initialize(message);
+                    break;
+                case MessageTypes.ChangeConfiguration:
+                    // TODO: what if the payload is null or represent empty string?
+                    _configure.Value = message.Payload.GetValue("Configuration");
+                    break;
+                case MessageTypes.RefreshDependencies:
+                    // In the case of RefreshDependencies request, the cache will not be reset in any case. The value 
+                    // is set so as to trigger refresh action in later loop.
+                    _refreshDependencies.Value = false;
+                    break;
+                case MessageTypes.RestoreComplete:
+                    // In the case of RestoreComplete request, the value of the 'Reset' property in payload will determine
+                    // if the cache should be reset. If the property doesn't exist, cache will be reset.
+                    _refreshDependencies.Value = message.Payload.HasValues ? message.Payload.Value<bool>("Reset") : true;
+                    break;
+                case MessageTypes.FilesChanged:
+                    _filesChanged.Value = 0;
+                    break;
+            }
+
+            return true;
+        }
+
+        private void Initialize(Message message)
+        {
+            if (_initializedContext != null)
+            {
+                Reporter.Output.WriteLine($"Received {message.MessageType} message more than once for {_appPath.Value}");
+                return;
+            }
+
+            _initializedContext = message.Sender;
+            _appPath.Value = message.Payload.GetValue("ProjectFolder");
+            _configure.Value = message.Payload.GetValue("Configuration") ?? "Debug";
+
+            var version = message.Payload.GetValue<int>("Version");
+            if (version != 0 && !_protocolManager.EnvironmentOverridden)
+            {
+                _contextProtocolVersion = Math.Min(version, _protocolManager.MaxVersion);
+                Reporter.Output.WriteLine($"Set context protocol version to {_contextProtocolVersion.Value}");
+            }
+        }
+
+        private bool UpdateProject()
+        {
+            ProjectSnapshot newSnapshot = null;
+
+            if (_appPath.WasAssigned || _configure.WasAssigned || _filesChanged.WasAssigned || _refreshDependencies.WasAssigned)
+            {
+                _appPath.ClearAssigned();
+                _configure.ClearAssigned();
+                _filesChanged.ClearAssigned();
+
+                bool resetCache = _refreshDependencies.WasAssigned ? _refreshDependencies.Value : false;
+                _refreshDependencies.ClearAssigned();
+
+                newSnapshot = ProjectSnapshot.Create(_appPath.Value,
+                                                     _configure.Value,
+                                                     _workspaceContext,
+                                                     _remote.ProjectSearchPaths,
+                                                     clearWorkspaceContextCache: resetCache);
+            }
+
+            if (newSnapshot == null)
+            {
+                return false;
+            }
+
+            _local = newSnapshot;
+
+            return true;
+        }
+
+        private void SendOutgingMessages()
+        {
+            _projectInforamtionMessenger.UpdateRemote(_local, _remote);
+            _projectDiagnosticsMessenger.UpdateRemote(_local, _remote);
+
+            var unprocessedFrameworks = new HashSet<NuGetFramework>(_remote.ProjectContexts.Keys);
+            foreach (var pair in _local.ProjectContexts)
+            {
+                ProjectContextSnapshot localProjectSnapshot = pair.Value;
+                ProjectContextSnapshot remoteProjectSnapshot;
+
+                if (!_remote.ProjectContexts.TryGetValue(pair.Key, out remoteProjectSnapshot))
+                {
+                    remoteProjectSnapshot = new ProjectContextSnapshot();
+                    _remote.ProjectContexts[pair.Key] = remoteProjectSnapshot;
+                }
+
+                unprocessedFrameworks.Remove(pair.Key);
+
+                foreach (var messenger in _messengers)
+                {
+                    messenger.UpdateRemote(localProjectSnapshot,
+                                           remoteProjectSnapshot);
+                }
+            }
+
+            // Remove all processed frameworks from the remote view
+            foreach (var framework in unprocessedFrameworks)
+            {
+                _remote.ProjectContexts.Remove(framework);
+            }
+
+            _globalErrorMessenger.UpdateRemote(_local, _remote);
+        }
+
+        private class Trigger<TValue>
+        {
+            private TValue _value;
+
+            public bool WasAssigned { get; private set; }
+
+            public void ClearAssigned()
+            {
+                WasAssigned = false;
+            }
+
+            public TValue Value
+            {
+                get { return _value; }
+                set
+                {
+                    WasAssigned = true;
+                    _value = value;
+                }
+            }
+        }
+    }
+}

src/dotnet/commands/dotnet-projectmodel-server/ProtocolManager.cs

@@ -0,0 +1,107 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using Microsoft.DotNet.Cli.Utils;
+using Microsoft.DotNet.ProjectModel.Server.Models;
+
+namespace Microsoft.DotNet.ProjectModel.Server
+{
+    internal class ProtocolManager
+    {
+        /// <summary>
+        /// Environment variable for overriding protocol.
+        /// </summary>
+        public const string EnvDthProtocol = "DTH_PROTOCOL";
+
+        public ProtocolManager(int maxVersion)
+        {
+            MaxVersion = maxVersion;
+
+            // initialized to the highest supported version or environment overridden value
+            int? protocol = GetProtocolVersionFromEnvironment();
+
+            if (protocol.HasValue)
+            {
+                CurrentVersion = protocol.Value;
+                EnvironmentOverridden = true;
+            }
+            else
+            {
+                CurrentVersion = 4;
+            }
+        }
+
+        public int MaxVersion { get; }
+
+        public int CurrentVersion { get; private set; }
+
+        public bool EnvironmentOverridden { get; }
+
+        public bool IsProtocolNegotiation(Message message)
+        {
+            return message?.MessageType == MessageTypes.ProtocolVersion;
+        }
+
+        public void Negotiate(Message message)
+        {
+            if (!IsProtocolNegotiation(message))
+            {
+                return;
+            }
+
+            Reporter.Output.WriteLine("Initializing the protocol negotiation.");
+
+            if (EnvironmentOverridden)
+            {
+                Reporter.Output.WriteLine($"DTH protocol negotiation is override by environment variable {EnvDthProtocol} and set to {CurrentVersion}.");
+                return;
+            }
+
+            var tokenValue = message.Payload?["Version"];
+            if (tokenValue == null)
+            {
+                Reporter.Output.WriteLine("Protocol negotiation failed. Version property is missing in payload.");
+                return;
+            }
+
+            var preferredVersion = tokenValue.ToObject<int>();
+            if (preferredVersion == 0)
+            {
+                // the preferred version can't be zero. either property is missing or the the payload is corrupted.
+                Reporter.Output.WriteLine("Protocol negotiation failed. Protocol version 0 is invalid.");
+                return;
+            }
+
+            CurrentVersion = Math.Min(preferredVersion, MaxVersion);
+            Reporter.Output.WriteLine($"Protocol negotiation successed. Use protocol {CurrentVersion}");
+
+            if (message.Sender != null)
+            {
+                Reporter.Output.WriteLine("Respond to protocol negotiation.");
+                message.Sender.Transmit(Message.FromPayload(
+                    MessageTypes.ProtocolVersion,
+                    0,
+                    new { Version = CurrentVersion }));
+            }
+            else
+            {
+                Reporter.Output.WriteLine($"{nameof(Message.Sender)} is null.");
+            }
+        }
+
+        private static int? GetProtocolVersionFromEnvironment()
+        {
+            // look for the environment variable DTH_PROTOCOL, if it is set override the protocol version.
+            // this is for debugging.
+            var strProtocol = Environment.GetEnvironmentVariable(EnvDthProtocol);
+            int intProtocol = -1;
+            if (!string.IsNullOrEmpty(strProtocol) && Int32.TryParse(strProtocol, out intProtocol))
+            {
+                return intProtocol;
+            }
+
+            return null;
+        }
+    }
+}