323 lines
11 KiB
Markdown
323 lines
11 KiB
Markdown
# net
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> Issue HTTP/HTTPS requests.
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The `net` module is a client-side API for issuing HTTP(S) requests. It is
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similar to the [HTTP](https://nodejs.org/api/http.html) and
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[HTTPS](https://nodejs.org/api/https.html) modules of Node.js but uses
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Chromium native networking library instead of the Node.js implementation
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offering therefore a much greater support regarding web proxies.
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Following is a non-exhaustive list of why you may consider using the `net`
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module instead of the native Node.js modules:
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* Automatic management of system proxy configuration, support of the wpad
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protocol and proxy pac configuration files.
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* Automatic tunneling of HTTPS requests.
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* Support for authenticating proxies using basic, digest, NTLM, Kerberos or
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negotiate authentication schemes.
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* Support for traffic monitoring proxies: Fiddler-like proxies used for access
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control and monitoring.
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The `net` module API has been specifically designed to mimic, as closely as
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possible, the familiar Node.js API. The API components including classes,
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methods, properties and event names are similar to those commonly used in
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Node.js.
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For instance, the following example quickly shows how the `net` API might be
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used:
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```javascript
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const {app} = require('electron')
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app.on('ready', () => {
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const {net} = require('electron')
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const request = net.request('https://github.com')
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request.on('response', (response) => {
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console.log(`STATUS: ${response.statusCode}`)
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console.log(`HEADERS: ${JSON.stringify(response.headers)}`)
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response.on('data', (chunk) => {
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console.log(`BODY: ${chunk}`)
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})
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response.on('end', () => {
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console.log('No more data in response.')
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})
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})
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request.end()
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})
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```
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By the way, it is almost identical to how you would normally use the
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[HTTP](https://nodejs.org/api/http.html)/[HTTPS](https://nodejs.org/api/https.html)
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modules of Node.js
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The `net` API can be used only after the application emits the `ready` event.
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Trying to use the module before the `ready` event will throw an error.
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## Methods
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The `net` module has the following methods:
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### `net.request(options)`
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* `options`: Object or String - The `ClientRequest` constructor options.
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Returns `ClientRequest`
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Creates a `ClientRequest` instance using the provided `options` which are
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directly forwarded to the `ClientRequest` constructor. The `net.request` method
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would be used to issue both secure and insecure HTTP requests according to the
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specified protocol scheme in the `options` object.
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## Class: ClientRequest
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`ClientRequest` implements the [Writable Stream](https://nodejs.org/api/stream.html#stream_writable_streams)
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interface and it is therefore an [EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter).
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### `new ClientRequest(options)`
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* `options` (Object | String) - If `options` is a String, it is interpreted as
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the request URL.
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If it is an object, it is expected to fully specify an HTTP request via the
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following properties:
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* `method` String (optional) - The HTTP request method. Defaults to the GET
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method.
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* `url` String (optional) - The request URL. Must be provided in the absolute
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form with the protocol scheme specified as http or https.
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* `session` Object (optional) - The [`Session`](session.md) instance with
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which the request is associated.
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* `partition` String (optional) - The name of the [`partition`](session.md)
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with which the request is associated. Defaults to the empty string. The
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`session` option prevails on `partition`. Thus if a `session` is explicitly
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specified, `partition` is ignored.
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* `protocol` String (optional) - The protocol scheme in the form 'scheme:'.
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Currently supported values are 'http:' or 'https:'. Defaults to 'http:'.
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* `host` String (optional) - The server host provided as a concatenation of
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the hostname and the port number 'hostname:port'
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* `hostname` String (optional) - The server host name.
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* `port` Integer (optional) - The server's listening port number.
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* `path` String (optional) - The path part of the request URL.
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`options` properties such as `protocol`, `host`, `hostname`, `port` and `path`
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strictly follow the Node.js model as described in the
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[URL](https://nodejs.org/api/url.html) module.
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For instance, we could have created the same request to 'github.com' as follows:
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```JavaScript
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const request = net.request({
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method: 'GET',
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protocol: 'https:',
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hostname: 'github.com',
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port: 443,
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path: '/'
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})
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```
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### Instance Events
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#### Event: 'response'
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Returns:
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* `response` IncomingMessage - An object representing the HTTP response message.
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#### Event: 'login'
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Returns:
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* `authInfo` Object
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* `isProxy` Boolean
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* `scheme` String
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* `host` String
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* `port` Integer
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* `realm` String
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* `callback` Function
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Emitted when an authenticating proxy is asking for user credentials.
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The `callback` function is expected to be called back with user credentials:
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* `username` String
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* `password` String
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```JavaScript
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request.on('login', (authInfo, callback) => {
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callback('username', 'password')
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})
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```
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Providing empty credentials will cancel the request and report an authentication
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error on the response object:
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```JavaScript
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request.on('response', (response) => {
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console.log(`STATUS: ${response.statusCode}`);
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response.on('error', (error) => {
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console.log(`ERROR: ${JSON.stringify(error)}`)
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})
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})
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request.on('login', (authInfo, callback) => {
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callback()
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})
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```
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#### Event: 'finish'
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Emitted just after the last chunk of the `request`'s data has been written into
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the `request` object.
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#### Event: 'abort'
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Emitted when the `request` is aborted. The `abort` event will not be fired if
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the `request` is already closed.
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#### Event: 'error'
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Returns:
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* `error` Error - an error object providing some information about the failure.
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Emitted when the `net` module fails to issue a network request. Typically when
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the `request` object emits an `error` event, a `close` event will subsequently
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follow and no response object will be provided.
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#### Event: 'close'
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Emitted as the last event in the HTTP request-response transaction. The `close`
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event indicates that no more events will be emitted on either the `request` or
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`response` objects.
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### Instance Properties
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#### `request.chunkedEncoding`
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A Boolean specifying whether the request will use HTTP chunked transfer encoding
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or not. Defaults to false. The property is readable and writable, however it can
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be set only before the first write operation as the HTTP headers are not yet put
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on the wire. Trying to set the `chunkedEncoding` property after the first write
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will throw an error.
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Using chunked encoding is strongly recommended if you need to send a large
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request body as data will be streamed in small chunks instead of being
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internally buffered inside Electron process memory.
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### Instance Methods
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#### `request.setHeader(name, value)`
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* `name` String - An extra HTTP header name.
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* `value` String - An extra HTTP header value.
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Adds an extra HTTP header. The header name will issued as it is without
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lowercasing. It can be called only before first write. Calling this method after
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the first write will throw an error.
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#### `request.getHeader(name)`
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* `name` String - Specify an extra header name.
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Returns String - The value of a previously set extra header name.
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#### `request.removeHeader(name)`
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* `name` String - Specify an extra header name.
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Removes a previously set extra header name. This method can be called only
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before first write. Trying to call it after the first write will throw an error.
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#### `request.write(chunk[, encoding][, callback])`
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* `chunk` (String | Buffer) - A chunk of the request body's data. If it is a
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string, it is converted into a Buffer using the specified encoding.
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* `encoding` String (optional) - Used to convert string chunks into Buffer
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objects. Defaults to 'utf-8'.
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* `callback` Function (optional) - Called after the write operation ends.
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`callback` is essentially a dummy function introduced in the purpose of keeping
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similarity with the Node.js API. It is called asynchronously in the next tick
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after `chunk` content have been delivered to the Chromium networking layer.
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Contrary to the Node.js implementation, it is not guaranteed that `chunk`
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content have been flushed on the wire before `callback` is called.
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Adds a chunk of data to the request body. The first write operation may cause
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the request headers to be issued on the wire. After the first write operation,
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it is not allowed to add or remove a custom header.
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#### `request.end([chunk][, encoding][, callback])`
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* `chunk` (String | Buffer) (optional)
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* `encoding` String (optional)
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* `callback` Function (optional)
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Sends the last chunk of the request data. Subsequent write or end operations
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will not be allowed. The `finish` event is emitted just after the end operation.
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#### `request.abort()`
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Cancels an ongoing HTTP transaction. If the request has already emitted the
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`close` event, the abort operation will have no effect. Otherwise an ongoing
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event will emit `abort` and `close` events. Additionally, if there is an ongoing
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response object,it will emit the `aborted` event.
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## Class: IncomingMessage
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`IncomingMessage` represents an HTTP response message.
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It is a [Readable Stream](https://nodejs.org/api/stream.html#stream_readable_streams)
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and consequently an [EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter).
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### Instance Events
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#### Event 'data'
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Returns:
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* `chunk`: Buffer - A chunk of response body's data.
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The `data` event is the usual method of transferring response data into
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applicative code.
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#### Event 'end'
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Indicates that response body has ended.
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#### Event 'aborted'
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Emitted when a request has been canceled during an ongoing HTTP transaction.
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#### Event 'error'
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Returns:
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`error` Error - Typically holds an error string identifying failure root cause.
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Emitted when an error was encountered while streaming response data events. For
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instance, if the server closes the underlying while the response is still
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streaming, an `error` event will be emitted on the response object and a `close`
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event will subsequently follow on the request object.
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### Instance properties
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An `IncomingMessage` instance has the following readable properties:
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#### `response.statusCode`
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An Integer indicating the HTTP response status code.
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#### `response.statusMessage`
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A String representing the HTTP status message.
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#### `response.headers`
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An Object representing the response HTTP headers. The `headers` object is
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formatted as follows:
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* All header names are lowercased.
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* Each header name produces an array-valued property on the headers object.
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* Each header value is pushed into the array associated with its header name.
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#### `response.httpVersion`
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A String indicating the HTTP protocol version number. Typical values are '1.0'
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or '1.1'. Additionally `httpVersionMajor` and `httpVersionMinor` are two
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Integer-valued readable properties that return respectively the HTTP major and
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minor version numbers.
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