256 lines
8.9 KiB
Markdown
256 lines
8.9 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 similar to the
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[HTTP](https://nodejs.org/api/http.html) and [HTTPS](https://nodejs.org/api/https.html) modules of Node.js
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but it uses Chromium native networking library instead of the Node.js implementation offering
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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` module instead of the native Node.js modules:
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* Automatic management of system proxy configuration, support of the wpad 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 negotiate authentication schemes.
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* Support for traffic monitoring proxies: Fiddler-like proxies used for access control and monitoring.
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The `net` module API has been specifically designed to mimic, as much closely as possible, the familiar Node.js API.
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The API components including classes, methods, properties and event names are similar to those commonly used in Node.js.
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For instance, the following example quickly shows how the `net` API might be 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 the way you would normally use the
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[HTTP](https://nodejs.org/api/http.html)/[HTTPS](https://nodejs.org/api/https.html) modules of Node.js
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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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Create a `ClientRequest` instance using the provided `options` object which is directly
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passed to the `ClientRequest` constructor. The `net.request` method would be used to issue
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both secure and insecure HTTP requests according to the 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) interface
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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 or String - If `options` is a String, it is interpreted as the request URL.
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If it is an object, it is expected to fully specify an HTTP request via the following properties:
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* `method` String (optional) - The HTTP request method. Defaults to the GET method.
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* `url` String (required) - The request URL. Must be provided in the absolute form with the protocol scheme specified as http or https.
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* `protocol` String (optional) - The protocol scheme in the form 'scheme:'. Current supported values are 'http:' or 'https:'. Defaults to 'http:'.
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* `host` String (optional) - The server host provided as a concatenation of a hostname and a 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 `protocol`, `host`, `hostname`, `port` and `path` strictly
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follow the Node.js model as described in the [URL](https://nodejs.org/api/url.html) module.
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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 an HTTP response message.
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#### Event: 'login'
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Returns:
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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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* `usrename` String
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* `password` String
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Providing empty credentials will cancel the request.
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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 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 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 the `request`
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object emits an error event, a close event will subsequently 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 event indicates
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that no more events will be emitted on either the `request` or `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 or
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not. Defaults to false. The property is readable and writable,
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however it can be set only before the first write operation as the HTTP headers are
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not yet put on the wire. Trying to set the `chunkedEncoding` property
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after a write will throw an error.
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Using chunked encoding is strongly recommended if you need to send a large request body as
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data will be streamed as small chunks instead of being internally buffered
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in Electron memory.
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### Instance Methods
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#### `request.setHeader(name, value)`
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* `name` String - An extra header name.
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* `value` String - An extra header value.
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Adds an extra HTTP header. The header name will issued as it is without lowercasing.
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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.
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#### `request.write(chunk[, encoding][, callback])`
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* `chunk` String or Buffer - A chunk of the request body' data. If it is a string,
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it is converted into a Buffer object using the specified encoding.
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* `encoding` String (optional) - Used to convert string chunks into Buffer objects. Defaults to 'utf-8'.
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* `callback` Function (optional) - Called after the write operation ends.
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Adds a chunk of data to the request body. Generally, the first write operation causes the request headers to be issued on the wire.
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After the first write operation, 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 or 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 will not
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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 closed, the abort operation will have no effect.
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Otherwise an ongoing event will emit abort and close events. Additionally, if there is an ongoing response object,
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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) and therefore
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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 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 if an error is encountered while streaming response data events. For instance,
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if the server closes the underlying socket while streaming the response, an error event
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will be emitted on the response object and a close event will subsequently follow in 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 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' or '1.1'. Additionally `httpVersionMajor` and
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`httpVersionMinor` are two Integer-valued readable properties that return respectively the HTTP major and minor version numbers.
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