# net

> Issue HTTP/HTTPS requests.

The `net` module is a client-side API for issuing HTTP(S) requests. It is similar to the 
[HTTP](https://nodejs.org/api/http.html)  and [HTTPS](https://nodejs.org/api/https.html) modules of Node.js 
but it uses Chromium native networking library instead of the Node.js implementation offering 
therefore a much greater support regarding web proxies.

Following is a non-exhaustive list of why you may consider using the `net` module instead of the native Node.js modules:
* Automatic management of system proxy configuration, support of the wpad protocol and proxy pac configuration files.
* Automatic tunneling of HTTPS requests.
* Support for authenticating proxies using basic, digest, NTLM, Kerberos or negotiate authentication schemes.
* Support for traffic monitoring proxies: Fiddler-like proxies used for access control and monitoring.

The `net` module API has been specifically designed to mimic, as much closely as possible, the familiar Node.js API.
The API components including classes, methods, properties and event names are similar to those commonly used in Node.js.

For instance, the following example quickly shows how the `net` API might be used:

```javascript
const {app} = require('electron')

app.on('ready', () => {
  
  const {net} = require('electron')

  const request = net.request('https://github.com')

  request.on('response', (response) => {

    console.log(`STATUS: ${response.statusCode}`);  
    console.log(`HEADERS: ${JSON.stringify(response.headers)}`);

    response.on('data', (chunk) => {
      console.log(`BODY: ${chunk}`)
    })

    response.on('end', () => {
      console.log('No more data in response.');
    })

  })

  request.end()
})
```

By the way, it is almost identical to the way you would normally use the
[HTTP](https://nodejs.org/api/http.html)/[HTTPS](https://nodejs.org/api/https.html) modules of Node.js

## Methods

The `net` module has the following methods:

### `net.request(options)`

* `options`: Object or String - The `ClientRequest` constructor options.

Returns `ClientRequest`

Create a `ClientRequest` instance using the provided `options` object which is directly
passed to the `ClientRequest` constructor. The `net.request` method would be used to issue
both secure and insecure HTTP requests according to the specified protocol scheme in the `options` object.

## Class: ClientRequest

`ClientRequest` implements the [Writable Stream](https://nodejs.org/api/stream.html#stream_writable_streams) interface
and it is therefore an [EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter).

### `new ClientRequest(options)`

* `options` Object or String - If `options` is a String, it is interpreted as the request URL. 
If it is an object, it is expected to fully specify an HTTP request via the following properties:
  * `method` String (optional) - The HTTP request method. Defaults to the GET method.
  * `url` String (required) - The request URL. Must be provided in the absolute form with the protocol scheme specified as http or https.
  * `protocol` String (optional) - The protocol scheme in the form 'scheme:'. Current supported values are 'http:' or 'https:'. Defaults to 'http:'.
  * `host` String (optional) - The server host provided as a concatenation of a hostname and a port number 'hostname:port'
  * `hostname` String (optional) - The server host name.
  * `port` Integer (optional) - The server's listening port number.
  * `path` String (optional) - The path part of the request URL. 
  
`options` properties `protocol`, `host`, `hostname`, `port` and `path` strictly 
follow the Node.js model as described in the [URL](https://nodejs.org/api/url.html) module.

### Instance Events

#### Event: 'response'

Returns:

* `response` IncomingMessage - An object representing an HTTP response message.

#### Event: 'login'

Returns:

* `authInfo` Object
  * `isProxy` Boolean
  * `scheme` String
  * `host` String
  * `port` Integer
  * `realm` String
* `callback` Function

Emitted when an authenticating proxy is asking for user credentials.

The `callback` function is expected to be called back with user credentials:

* `usrename` String
* `password` String

```JavaScript
request.on('login', (authInfo, callback) => {
  callback('username', 'password')
})
```
Providing empty credentials will cancel the request and report an authentication error on the response object:

```JavaScript
request.on('response', (response) => {
  console.log(`STATUS: ${response.statusCode}`);
  response.on('error', (error) => {
    console.log(`ERROR: ${JSON.stringify(error)}`)
  })
})
request.on('login', (authInfo, callback) => {
  callback()
})
```

#### Event: 'finish'

Emitted just after the last chunk of the `request`'s data has been written into the `request` object.

#### Event: 'abort'

Emitted when the `request` is aborted. The abort event will not be fired if the `request` is already closed.

#### Event: 'error'

Returns:

* `error` Error - an error object providing some information about the failure.

Emitted when the `net` module fails to issue a network request. Typically when the `request`
object emits an error event, a close event will subsequently follow and no response object will be provided.

#### Event: 'close'

Emitted as the last event in the HTTP request-response transaction. The close event indicates
that no more events will be emitted on either the `request` or `response` objects.

### Instance Properties

#### `request.chunkedEncoding`

A Boolean specifying whether the request will use HTTP chunked transfer encoding or
not. Defaults to false. The property is readable and writable, 
however it can be set only before the first write operation as the HTTP headers are
not yet put on the wire. Trying to set the `chunkedEncoding` property
after a write will throw an error.

Using chunked encoding is strongly recommended if you need to send a large request body as
data will be streamed as small chunks instead of being internally buffered 
in Electron memory.

### Instance Methods

#### `request.setHeader(name, value)`

* `name` String - An extra header name.
* `value` String - An extra header value.

Adds an extra HTTP header. The header name will issued as it is without lowercasing.

#### `request.getHeader(name)`

* `name` String - Specify an extra header name.

Returns String - The value of a previously set extra header name.

#### `request.removeHeader(name)`

* `name` String - Specify an extra header name.

Removes a previously set extra header name. 

#### `request.write(chunk[, encoding][, callback])`

* `chunk` String or Buffer - A chunk of the request body' data. If it is a string,
it is converted into a Buffer object using the specified encoding.
* `encoding` String (optional) - Used to convert string chunks into Buffer objects. Defaults to 'utf-8'.
* `callback` Function (optional) - Called after the write operation ends.

Adds a chunk of data to the request body. Generally, the first write operation causes the request headers to be issued on the wire. 
After the first write operation, it is not allowed to add or remove a custom header.

#### `request.end([chunk][, encoding][, callback])`

* `chunk` String or Buffer (optional)
* `encoding` String (optional)
* `callback` Function (optional)

Sends the last chunk of the request data. Subsequent write or end operations will not
be allowed. The finish event is emitted just after the end operation.

#### `request.abort()`

Cancels an ongoing HTTP transaction. If the request has already closed, the abort operation will have no effect. 
Otherwise an ongoing event will emit abort and close events. Additionally, if there is an ongoing response object,
it will emit the aborted event.


## Class: IncomingMessage

`IncomingMessage` represents an HTTP response message.
It is a [Readable Stream](https://nodejs.org/api/stream.html#stream_readable_streams) and therefore 
an [EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter).

### Instance Events

#### Event 'data'

Returns:

* `chunk`: Buffer - A chunk of response body's data.

The data event is the usual method of transferring response data into applicative code. 

#### Event 'end'

Indicates that response body has ended.

#### Event 'aborted'

Emitted when a request has been canceled during an ongoing HTTP transaction.

#### Event 'error'

Returns

`error` Error - Typically holds an error string identifying failure root cause.

Emitted if an error is encountered while streaming response data events. For instance, 
if the server closes the underlying socket while streaming the response, an error event 
will be emitted on the response object and a close event will subsequently follow in the request object.

### Instance properties

An `IncomingMessage` instance has the following readable properties:

#### `response.statusCode`

An Integer indicating the HTTP response status code.

#### `response.statusMessage`

A String representing the HTTP status message.

#### `response.headers`

An Object representing the response HTTP headers. The `headers` object is formatted as follows:

* All header names are lowercased.
* Each header name produces an array-valued property on the headers object.
* Each header value is pushed into the array associated with its header name.

#### `response.httpVersion`

A String indicating the HTTP protocol version number. Typical values are '1.0' or '1.1'. Additionally `httpVersionMajor` and
`httpVersionMinor` are two Integer-valued readable properties that return respectively the HTTP major and minor version numbers.