Making the reporing channel port discovery and accept incoming connections separate. Before we were hanging when creating the reporting channel and never starting the test runner.

src/dotnet/commands/dotnet-test/IReportingChannel.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System;
+using System.Threading.Tasks;
 using Microsoft.Extensions.Testing.Abstractions;
 
 namespace Microsoft.DotNet.Tools.Test
@@ -12,6 +13,8 @@ namespace Microsoft.DotNet.Tools.Test
 
         int Port { get; }
 
+        void Accept();
+
         void Send(Message message);
 
         void SendError(string error);

src/dotnet/commands/dotnet-test/MessageHandlers/GetTestRunnerProcessStartInfoMessageHandler.cs

@@ -41,6 +41,8 @@ namespace Microsoft.DotNet.Tools.Test
 
             dotnetTest.StartListeningTo(testRunnerChannel);
 
+            testRunnerChannel.Accept();
+
             var testRunner = _testRunnerFactory.CreateTestRunner(
                 new RunTestsArgumentsBuilder(dotnetTest.PathToAssemblyUnderTest, testRunnerChannel.Port, message));
 

src/dotnet/commands/dotnet-test/MessageHandlers/TestDiscoveryStartMessageHandler.cs

@@ -55,6 +55,8 @@ namespace Microsoft.DotNet.Cli.Tools.Test
 
                 dotnetTest.StartListeningTo(testRunnerChannel);
 
+                testRunnerChannel.Accept();
+
                 var testRunner = _testRunnerFactory.CreateTestRunner(
                     new DiscoverTestsArgumentsBuilder(dotnetTest.PathToAssemblyUnderTest, testRunnerChannel.Port));
 

src/dotnet/commands/dotnet-test/Program.cs

@@ -141,6 +141,8 @@ namespace Microsoft.DotNet.Tools.Test
 
                     dotnetTest.StartListeningTo(adapterChannel);
 
+                    adapterChannel.Accept();
+
                     dotnetTest.StartHandlingMessages();
                 }
             }

src/dotnet/commands/dotnet-test/ReportingChannel.cs

@@ -7,6 +7,7 @@ using System.IO;
 using System.Net;
 using System.Net.Sockets;
 using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.Extensions.Testing.Abstractions;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
@@ -18,37 +19,47 @@ namespace Microsoft.DotNet.Tools.Test
         public static ReportingChannel ListenOn(int port)
         {
             // This fixes the mono incompatibility but ties it to ipv4 connections
-            using (var listenSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
+            var listenSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
-            {
-                listenSocket.Bind(new IPEndPoint(IPAddress.Loopback, port));
-                listenSocket.Listen(10);
 
-                var socket = listenSocket.Accept();
+            listenSocket.Bind(new IPEndPoint(IPAddress.Loopback, port));
+            listenSocket.Listen(10);
 
-                return new ReportingChannel(socket);
+            return new ReportingChannel(listenSocket);
-            }
         }
 
-        private readonly BinaryWriter _writer;
+        private BinaryWriter _writer;
-        private readonly BinaryReader _reader;
+        private BinaryReader _reader;
+        private Socket _listenSocket;
 
-        private ReportingChannel(Socket socket)
+        private ReportingChannel(Socket listenSocket)
         {
-            Socket = socket;
+            _listenSocket = listenSocket;
-
+            Port = ((IPEndPoint)listenSocket.LocalEndPoint).Port;
-            var stream = new NetworkStream(Socket);
-            _writer = new BinaryWriter(stream);
-            _reader = new BinaryReader(stream);
-
-            // Read incoming messages on the background thread
-            new Thread(ReadMessages) { IsBackground = true }.Start();
         }
 
         public event EventHandler<Message> MessageReceived;
 
         public Socket Socket { get; private set; }
 
-        public int Port => ((IPEndPoint) Socket.LocalEndPoint).Port;
+        public int Port { get; }
+
+        public void Accept()
+        {
+            new Thread(() =>
+            {
+                using (_listenSocket)
+                {
+                    Socket = _listenSocket.Accept();
+
+                    var stream = new NetworkStream(Socket);
+                    _writer = new BinaryWriter(stream);
+                    _reader = new BinaryReader(stream);
+
+                    // Read incoming messages on the background thread
+                    new Thread(ReadMessages) { IsBackground = true }.Start();
+                }
+            }) { IsBackground = true }.Start();
+        }
 
         public void Send(Message message)
         {
@@ -99,7 +110,8 @@ namespace Microsoft.DotNet.Tools.Test
             {
                 try
                 {
-                    var message = JsonConvert.DeserializeObject<Message>(_reader.ReadString());
+                    var rawMessage = _reader.ReadString();
+                    var message = JsonConvert.DeserializeObject<Message>(rawMessage);
 
                     MessageReceived?.Invoke(this, message);
                 }

test/dotnet-test.UnitTests/GivenATestDiscoveryStartMessageHandler.cs

@@ -134,6 +134,16 @@ namespace Microsoft.Dotnet.Tools.Test.Tests
             _reportingChannelFactoryMock.Verify(r => r.CreateChannelWithAnyAvailablePort(), Times.Once);
         }
 
+        [Fact]
+        public void It_calls_accept_on_the_test_runner_channel()
+        {
+            _testDiscoveryStartMessageHandler.HandleMessage(
+                    _dotnetTestMock.Object,
+                    _validMessage);
+
+            _testRunnerChannelMock.Verify(t => t.Accept(), Times.Once);
+        }
+
         [Fact]
         public void It_makes_dotnet_test_listen_on_the_test_runner_port_for_messages_when_it_handles_the_message()
         {

test/dotnet-test.UnitTests/GivenATestExecutionGetTestRunnerProcessStartInfoMessageHandler.cs

@@ -148,6 +148,16 @@ namespace Microsoft.Dotnet.Tools.Test.Tests
             _reportingChannelFactoryMock.Verify(r => r.CreateChannelWithAnyAvailablePort(), Times.Once);
         }
 
+        [Fact]
+        public void It_calls_accept_on_the_test_runner_channel()
+        {
+            _testGetTestRunnerProcessStartInfoMessageHandler.HandleMessage(
+                    _dotnetTestMock.Object,
+                    _validMessage);
+
+            _testRunnerChannelMock.Verify(t => t.Accept(), Times.Once);
+        }
+
         [Fact]
         public void It_makes_dotnet_test_listen_on_the_test_runner_port_for_messages_when_it_handles_the_message()
         {