ClientRequest.onSocket method | Node.js http module | Bun

ClientRequest.onSocket method | Node.js http module | BunBuildDocsReferenceGuidesBlogDiscord/node:http/ClientRequest/onSocketMonSocket

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http.ClientRequest.onSocketonSocket(socket: Socket): void;Referenced typesclass SocketThis class is an abstraction of a TCP socket or a streaming IPC endpoint (uses named pipes on Windows, and Unix domain sockets otherwise). It is also an EventEmitter.

A net.Socket can be created by the user and used directly to interact with a server. For example, it is returned by createConnection, so the user can use it to talk to the server.

It can also be created by Node.js and passed to the user when a connection is received. For example, it is passed to the listeners of a 'connection' event emitted on a Server, so the user can use it to interact with the client.

allowHalfOpen: booleanIf false then the stream will automatically end the writable side when the readable side ends. Set initially by the allowHalfOpen constructor option, which defaults to true.

This can be changed manually to change the half-open behavior of an existing Duplex stream instance, but must be changed before the 'end' event is emitted.

readonly autoSelectFamilyAttemptedAddresses: string[]This property is only present if the family autoselection algorithm is enabled in socket.connect(options) and it is an array of the addresses that have been attempted.

Each address is a string in the form of $IP:$PORT. If the connection was successful, then the last address is the one that the socket is currently connected to.

readonly bytesRead: numberThe amount of received bytes.

readonly bytesWritten: numberThe amount of bytes sent.

readonly closed: booleanIs true after 'close' has been emitted.

readonly connecting: booleanIf true, socket.connect(options[, connectListener]) was called and has not yet finished. It will stay true until the socket becomes connected, then it is set to false and the 'connect' event is emitted. Note that the socket.connect(options[, connectListener]) callback is a listener for the 'connect' event.

readonly destroyed: booleanSee writable.destroyed for further details.

readonly errored: null | ErrorReturns error if the stream has been destroyed with an error.

readonly localAddress?: stringThe string representation of the local IP address the remote client is connecting on. For example, in a server listening on '0.0.0.0', if a client connects on '192.168.1.1', the value of socket.localAddress would be'192.168.1.1'.

readonly localFamily?: stringThe string representation of the local IP family. 'IPv4' or 'IPv6'.

readonly localPort?: numberThe numeric representation of the local port. For example, 80 or 21.

readonly pending: booleanThis is true if the socket is not connected yet, either because .connect()has not yet been called or because it is still in the process of connecting (see socket.connecting).

readable: booleanIs true if it is safe to call read, which means the stream has not been destroyed or emitted 'error' or 'end'.

readonly readableAborted: booleanReturns whether the stream was destroyed or errored before emitting 'end'.

readonly readableDidRead: booleanReturns whether 'data' has been emitted.

readonly readableEncoding: null | BufferEncodingGetter for the property encoding of a given Readable stream. The encoding property can be set using the setEncoding method.

readonly readableEnded: booleanBecomes true when 'end' event is emitted.

readableFlowing: null | booleanThis property reflects the current state of a Readable stream as described in the Three states section.

readonly readableHighWaterMark: numberReturns the value of highWaterMark passed when creating this Readable.

readonly readableLength: numberThis property contains the number of bytes (or objects) in the queue ready to be read. The value provides introspection data regarding the status of the highWaterMark.

readonly readableObjectMode: booleanGetter for the property objectMode of a given Readable stream.

readonly readyState: SocketReadyStateThis property represents the state of the connection as a string.

If the stream is connecting socket.readyState is opening.If the stream is readable and writable, it is open.If the stream is readable and not writable, it is readOnly.If the stream is not readable and writable, it is writeOnly.readonly remoteAddress: undefined | stringThe string representation of the remote IP address. For example,'74.125.127.100' or '2001:4860:a005::68'. Value may be undefined if the socket is destroyed (for example, if the client disconnected).

readonly remoteFamily: undefined | stringThe string representation of the remote IP family. 'IPv4' or 'IPv6'. Value may be undefined if the socket is destroyed (for example, if the client disconnected).

readonly remotePort: undefined | numberThe numeric representation of the remote port. For example, 80 or 21. Value may be undefined if the socket is destroyed (for example, if the client disconnected).

readonly timeout?: numberThe socket timeout in milliseconds as set by socket.setTimeout(). It is undefined if a timeout has not been set.

writable: booleanIs true if it is safe to call writable.write(), which means the stream has not been destroyed, errored, or ended.

readonly writableAborted: booleanReturns whether the stream was destroyed or errored before emitting 'finish'.

readonly writableCorked: numberNumber of times writable.uncork() needs to be called in order to fully uncork the stream.

readonly writableEnded: booleanIs true after writable.end() has been called. This property does not indicate whether the data has been flushed, for this use writable.writableFinished instead.

readonly writableFinished: booleanIs set to true immediately before the 'finish' event is emitted.

readonly writableHighWaterMark: numberReturn the value of highWaterMark passed when creating this Writable.

readonly writableLength: numberThis property contains the number of bytes (or objects) in the queue ready to be written. The value provides introspection data regarding the status of the highWaterMark.

readonly writableNeedDrain: booleanIs true if the stream's buffer has been full and stream will emit 'drain'.

readonly writableObjectMode: booleanGetter for the property objectMode of a given Writable stream.

_construct(callback: (error?: null | Error) => void): void;_destroy(error: null | Error,callback: (error?: null | Error) => void): void;_final(callback: (error?: null | Error) => void): void;_read(size: number): void;_write(chunk: any,encoding: BufferEncoding,callback: (error?: null | Error) => void): void;_writev(chunks: { chunk: any; encoding: BufferEncoding }[],callback: (error?: null | Error) => void): void;[Symbol.asyncDispose](): Promisevoid>;Calls readable.destroy() with an AbortError and returns a promise that fulfills when the stream is finished.

[Symbol.asyncIterator](): AsyncIteratorany>;@returnsAsyncIterator to fully consume the stream.

[events.captureRejectionSymbol](error: Error,event: string | symbol,...args: any[]): void;The Symbol.for('nodejs.rejection') method is called in case a promise rejection happens when emitting an event and captureRejections is enabled on the emitter. It is possible to use events.captureRejectionSymbol in place of Symbol.for('nodejs.rejection').

import { EventEmitter, captureRejectionSymbol } from 'node:events'; class MyClass extends EventEmitter { constructor() { super({ captureRejections: true }); } [captureRejectionSymbol](err, event, ...args) { console.log('rejection happened for', event, 'with', err, ...args); this.destroy(err); } destroy(err) { // Tear the resource down here. } } addListenerE extends keyof SocketEventMap>(eventName: E,listener: (...args: SocketEventMap[E]) => void): this;Alias for emitter.on(eventName, listener).

addListener(eventName: string | symbol,listener: (...args: any[]) => void): this;address(): {} | AddressInfo;Returns the bound address, the address family name and port of the socket as reported by the operating system:{ port: 12346, family: 'IPv4', address: '127.0.0.1' }

compose(stream: WritableStream | WritableStreamany> | TransformStreamany, any> | (source: any) => void,options?: Abortable): Duplex;import { Readable } from 'node:stream'; async function* splitToWords(source) { for await (const chunk of source) { const words = String(chunk).split(' '); for (const word of words) { yield word; } } } const wordsStream = Readable.from(['this is', 'compose as operator']).compose(splitToWords); const words = await wordsStream.toArray(); console.log(words); // prints ['this', 'is', 'compose', 'as', 'operator'] See stream.compose for more information.

@returnsa stream composed with the stream stream.

connect(options: SocketConnectOpts,connectionListener?: () => void): this;Initiate a connection on a given socket.

Possible signatures:

socket.connect(options[, connectListener])socket.connect(path[, connectListener]) for IPC connections.socket.connect(port[, host][, connectListener]) for TCP connections.Returns: net.Socket The socket itself.This function is asynchronous. When the connection is established, the 'connect' event will be emitted. If there is a problem connecting, instead of a 'connect' event, an 'error' event will be emitted with the error passed to the 'error' listener. The last parameter connectListener, if supplied, will be added as a listener for the 'connect' event once.

This function should only be used for reconnecting a socket after'close' has been emitted or otherwise it may lead to undefined behavior.

connect(port: number,host: string,connectionListener?: () => void): this;Initiate a connection on a given socket.

Possible signatures:

socket.connect(options[, connectListener])socket.connect(path[, connectListener]) for IPC connections.socket.connect(port[, host][, connectListener]) for TCP connections.Returns: net.Socket The socket itself.This function is asynchronous. When the connection is established, the 'connect' event will be emitted. If there is a problem connecting, instead of a 'connect' event, an 'error' event will be emitted with the error passed to the 'error' listener. The last parameter connectListener, if supplied, will be added as a listener for the 'connect' event once.

This function should only be used for reconnecting a socket after'close' has been emitted or otherwise it may lead to undefined behavior.

connect(port: number,connectionListener?: () => void): this;Initiate a connection on a given socket.

Possible signatures:

socket.connect(options[, connectListener])socket.connect(path[, connectListener]) for IPC connections.socket.connect(port[, host][, connectListener]) for TCP connections.Returns: net.Socket The socket itself.This function is asynchronous. When the connection is established, the 'connect' event will be emitted. If there is a problem connecting, instead of a 'connect' event, an 'error' event will be emitted with the error passed to the 'error' listener. The last parameter connectListener, if supplied, will be added as a listener for the 'connect' event once.

This function should only be used for reconnecting a socket after'close' has been emitted or otherwise it may lead to undefined behavior.

connect(path: string,connectionListener?: () => void): this;Initiate a connection on a given socket.

Possible signatures:

socket.connect(options[, connectListener])socket.connect(path[, connectListener]) for IPC connections.socket.connect(port[, host][, connectListener]) for TCP connections.Returns: net.Socket The socket itself.This function is asynchronous. When the connection is established, the 'connect' event will be emitted. If there is a problem connecting, instead of a 'connect' event, an 'error' event will be emitted with the error passed to the 'error' listener. The last parameter connectListener, if supplied, will be added as a listener for the 'connect' event once.

This function should only be used for reconnecting a socket after'close' has been emitted or otherwise it may lead to undefined behavior.

cork(): void;The writable.cork() method forces all written data to be buffered in memory. The buffered data will be flushed when either the uncork or end methods are called.

The primary intent of writable.cork() is to accommodate a situation in which several small chunks are written to the stream in rapid succession. Instead of immediately forwarding them to the underlying destination, writable.cork() buffers all the chunks until writable.uncork() is called, which will pass them all to writable._writev(), if present. This prevents a head-of-line blocking situation where data is being buffered while waiting for the first small chunk to be processed. However, use of writable.cork() without implementing writable._writev() may have an adverse effect on throughput.

See also: writable.uncork(), writable._writev().

destroy(error?: Error): this;Destroy the stream. Optionally emit an 'error' event, and emit a 'close' event (unless emitClose is set to false). After this call, the readable stream will release any internal resources and subsequent calls to push() will be ignored.

Once destroy() has been called any further calls will be a no-op and no further errors except from _destroy() may be emitted as 'error'.

Implementors should not override this method, but instead implement readable._destroy().

@param errorError which will be passed as payload in 'error' event

destroySoon(): void;Destroys the socket after all data is written. If the finish event was already emitted the socket is destroyed immediately. If the socket is still writable it implicitly calls socket.end().

drop(limit: number,options?: Abortable): Readable;This method returns a new stream with the first limit chunks dropped from the start.

@param limitthe number of chunks to drop from the readable.

@returnsa stream with limit chunks dropped from the start.

emitE extends keyof SocketEventMap>(eventName: E,...args: SocketEventMap[E]): boolean;Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each.

Returns true if the event had listeners, false otherwise.

import { EventEmitter } from 'node:events'; const myEmitter = new EventEmitter(); // First listener myEmitter.on('event', function firstListener() { console.log('Helloooo! first listener'); }); // Second listener myEmitter.on('event', function secondListener(arg1, arg2) { console.log(`event with parameters ${arg1}, ${arg2} in second listener`); }); // Third listener myEmitter.on('event', function thirdListener(...args) { const parameters = args.join(', '); console.log(`event with parameters ${parameters} in third listener`); }); console.log(myEmitter.listeners('event')); myEmitter.emit('event', 1, 2, 3, 4, 5); // Prints: // [ // [Function: firstListener], // [Function: secondListener], // [Function: thirdListener] // ] // Helloooo! first listener // event with parameters 1, 2 in second listener // event with parameters 1, 2, 3, 4, 5 in third listener emit(eventName: string | symbol,...args: any[]): boolean;end(callback?: () => void): this;Half-closes the socket. i.e., it sends a FIN packet. It is possible the server will still send some data.

See writable.end() for further details.

@param callbackOptional callback for when the socket is finished.

@returnsThe socket itself.

end(buffer: string | Uint8ArrayArrayBufferLike>,callback?: () => void): this;Half-closes the socket. i.e., it sends a FIN packet. It is possible the server will still send some data.

See writable.end() for further details.

@param callbackOptional callback for when the socket is finished.

@returnsThe socket itself.

end(str: string | Uint8ArrayArrayBufferLike>,encoding?: BufferEncoding,callback?: () => void): this;Half-closes the socket. i.e., it sends a FIN packet. It is possible the server will still send some data.

See writable.end() for further details.

@param encodingOnly used when data is string.

@param callbackOptional callback for when the socket is finished.

@returnsThe socket itself.

{}); myEE.on('bar', () => {}); const sym = Symbol('symbol'); myEE.on(sym, () => {}); console.log(myEE.eventNames()); // Prints: [ 'foo', 'bar', Symbol(symbol) ] ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">eventNames(): string | symbol[];Returns an array listing the events for which the emitter has registered listeners.

import { EventEmitter } from 'node:events'; const myEE = new EventEmitter(); myEE.on('foo', () => {}); myEE.on('bar', () => {}); const sym = Symbol('symbol'); myEE.on(sym, () => {}); console.log(myEE.eventNames()); // Prints: [ 'foo', 'bar', Symbol(symbol) ] every(fn: (data: any, options?: Abortable) => boolean | Promiseboolean>,options?: PickReadableOperatorOptions, 'signal' | 'concurrency'>): Promiseboolean>;This method is similar to Array.prototype.every and calls fn on each chunk in the stream to check if all awaited return values are truthy value for fn. Once an fn call on a chunk awaited return value is falsy, the stream is destroyed and the promise is fulfilled with false. If all of the fn calls on the chunks return a truthy value, the promise is fulfilled with true.

@param fna function to call on each chunk of the stream. Async or not.

@returnsa promise evaluating to true if fn returned a truthy value for every one of the chunks.

filter(fn: (data: any, options?: Abortable) => boolean | Promiseboolean>,options?: ReadableOperatorOptions): Readable;This method allows filtering the stream. For each chunk in the stream the fn function will be called and if it returns a truthy value, the chunk will be passed to the result stream. If the fn function returns a promise - that promise will be awaited.

@param fna function to filter chunks from the stream. Async or not.

@returnsa stream filtered with the predicate fn.

findT>(fn: (data: any, options?: Abortable) => data is T,options?: PickReadableOperatorOptions, 'signal' | 'concurrency'>): Promiseundefined | T>;This method is similar to Array.prototype.find and calls fn on each chunk in the stream to find a chunk with a truthy value for fn. Once an fn call's awaited return value is truthy, the stream is destroyed and the promise is fulfilled with value for which fn returned a truthy value. If all of the fn calls on the chunks return a falsy value, the promise is fulfilled with undefined.

@param fna function to call on each chunk of the stream. Async or not.

@returnsa promise evaluating to the first chunk for which fn evaluated with a truthy value, or undefined if no element was found.

find(fn: (data: any, options?: Abortable) => boolean | Promiseboolean>,options?: PickReadableOperatorOptions, 'signal' | 'concurrency'>): Promiseany>;This method is similar to Array.prototype.find and calls fn on each chunk in the stream to find a chunk with a truthy value for fn. Once an fn call's awaited return value is truthy, the stream is destroyed and the promise is fulfilled with value for which fn returned a truthy value. If all of the fn calls on the chunks return a falsy value, the promise is fulfilled with undefined.

@param fna function to call on each chunk of the stream. Async or not.

@returnsa promise evaluating to the first chunk for which fn evaluated with a truthy value, or undefined if no element was found.

flatMap(fn: (data: any, options?: Abortable) => any,options?: PickReadableOperatorOptions, 'signal' | 'concurrency'>): Readable;This method returns a new stream by applying the given callback to each chunk of the stream and then flattening the result.

It is possible to return a stream or another iterable or async iterable from fn and the result streams will be merged (flattened) into the returned stream.

@param fna function to map over every chunk in the stream. May be async. May be a stream or generator.

@returnsa stream flat-mapped with the function fn.

forEach(fn: (data: any, options?: Abortable) => void | Promisevoid>,options?: PickReadableOperatorOptions, 'signal' | 'concurrency'>): Promisevoid>;This method allows iterating a stream. For each chunk in the stream the fn function will be called. If the fn function returns a promise - that promise will be awaited.

This method is different from for await...of loops in that it can optionally process chunks concurrently. In addition, a forEach iteration can only be stopped by having passed a signal option and aborting the related AbortController while for await...of can be stopped with break or return. In either case the stream will be destroyed.

This method is different from listening to the 'data' event in that it uses the readable event in the underlying machinary and can limit the number of concurrent fn calls.

@param fna function to call on each chunk of the stream. Async or not.

@returnsa promise for when the stream has finished.

getMaxListeners(): number;Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to events.defaultMaxListeners.

isPaused(): boolean;The readable.isPaused() method returns the current operating state of the Readable. This is used primarily by the mechanism that underlies the readable.pipe() method. In most typical cases, there will be no reason to use this method directly.

const readable = new stream.Readable(); readable.isPaused(); // === false readable.pause(); readable.isPaused(); // === true readable.resume(); readable.isPaused(); // === false iterator(options?: ReadableIteratorOptions): AsyncIteratorany>;The iterator created by this method gives users the option to cancel the destruction of the stream if the for await...of loop is exited by return, break, or throw, or if the iterator should destroy the stream if the stream emitted an error during iteration.

listenerCountE extends keyof SocketEventMap>(eventName: E,listener?: (...args: SocketEventMap[E]) => void): number;Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

@param eventNameThe name of the event being listened for

@param listenerThe event handler function

listenerCount(eventName: string | symbol,listener?: (...args: any[]) => void): number; { console.log('someone connected!'); }); console.log(util.inspect(server.listeners('connection'))); // Prints: [ [Function] ] ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">listenersE extends keyof SocketEventMap>(eventName: E): (...args: SocketEventMap[E]) => void[];Returns a copy of the array of listeners for the event named eventName.

server.on('connection', (stream) => { console.log('someone connected!'); }); console.log(util.inspect(server.listeners('connection'))); // Prints: [ [Function] ] listeners(eventName: string | symbol): (...args: any[]) => void[];map(fn: (data: any, options?: Abortable) => any,options?: ReadableOperatorOptions): Readable;This method allows mapping over the stream. The fn function will be called for every chunk in the stream. If the fn function returns a promise - that promise will be awaited before being passed to the result stream.

@param fna function to map over every chunk in the stream. Async or not.

@returnsa stream mapped with the function fn.

offE extends keyof SocketEventMap>(eventName: E,listener: (...args: SocketEventMap[E]) => void): this;Alias for emitter.removeListener().

off(eventName: string | symbol,listener: (...args: any[]) => void): this; { console.log('someone connected!'); }); ``` Returns a reference to the `EventEmitter`, so that calls can be chained. By default, event listeners are invoked in the order they are added. The `emitter.prependListener()` method can be used as an alternative to add the event listener to the beginning of the listeners array. ```js import { EventEmitter } from 'node:events'; const myEE = new EventEmitter(); myEE.on('foo', () => console.log('a')); myEE.prependListener('foo', () => console.log('b')); myEE.emit('foo'); // Prints: // b // a ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">onE extends keyof SocketEventMap>(eventName: E,listener: (...args: SocketEventMap[E]) => void): this;Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

server.on('connection', (stream) => { console.log('someone connected!'); }); Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

import { EventEmitter } from 'node:events'; const myEE = new EventEmitter(); myEE.on('foo', () => console.log('a')); myEE.prependListener('foo', () => console.log('b')); myEE.emit('foo'); // Prints: // b // a @param eventNameThe name of the event.

@param listenerThe callback function

on(eventName: string | symbol,listener: (...args: any[]) => void): this; { console.log('Ah, we have our first user!'); }); ``` Returns a reference to the `EventEmitter`, so that calls can be chained. By default, event listeners are invoked in the order they are added. The `emitter.prependOnceListener()` method can be used as an alternative to add the event listener to the beginning of the listeners array. ```js import { EventEmitter } from 'node:events'; const myEE = new EventEmitter(); myEE.once('foo', () => console.log('a')); myEE.prependOnceListener('foo', () => console.log('b')); myEE.emit('foo'); // Prints: // b // a ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">onceE extends keyof SocketEventMap>(eventName: E,listener: (...args: SocketEventMap[E]) => void): this;Adds a one-time listener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.

server.once('connection', (stream) => { console.log('Ah, we have our first user!'); }); Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. The emitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

import { EventEmitter } from 'node:events'; const myEE = new EventEmitter(); myEE.once('foo', () => console.log('a')); myEE.prependOnceListener('foo', () => console.log('b')); myEE.emit('foo'); // Prints: // b // a @param eventNameThe name of the event.

@param listenerThe callback function

once(eventName: string | symbol,listener: (...args: any[]) => void): this;pause(): this;Pauses the reading of data. That is, 'data' events will not be emitted. Useful to throttle back an upload.

@returnsThe socket itself.

pipeT extends WritableStream>(destination: T,options?: PipeOptions): T; { console.log('someone connected!'); }); ``` Returns a reference to the `EventEmitter`, so that calls can be chained." data-algolia-static="false" data-algolia-merged="false" data-type="Method">prependListenerE extends keyof SocketEventMap>(eventName: E,listener: (...args: SocketEventMap[E]) => void): this;Adds the listener function to the beginning of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

server.prependListener('connection', (stream) => { console.log('someone connected!'); }); Returns a reference to the EventEmitter, so that calls can be chained.

@param eventNameThe name of the event.

@param listenerThe callback function

prependListener(eventName: string | symbol,listener: (...args: any[]) => void): this; { console.log('Ah, we have our first user!'); }); ``` Returns a reference to the `EventEmitter`, so that calls can be chained." data-algolia-static="false" data-algolia-merged="false" data-type="Method">prependOnceListenerE extends keyof SocketEventMap>(eventName: E,listener: (...args: SocketEventMap[E]) => void): this;Adds a one-time listener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this listener is removed, and then invoked.

server.prependOnceListener('connection', (stream) => { console.log('Ah, we have our first user!'); }); Returns a reference to the EventEmitter, so that calls can be chained.

@param eventNameThe name of the event.

@param listenerThe callback function

prependOnceListener(eventName: string | symbol,listener: (...args: any[]) => void): this;push(chunk: any,encoding?: BufferEncoding): boolean; console.log('log once')); // Returns a new Array with a function `onceWrapper` which has a property // `listener` which contains the original listener bound above const listeners = emitter.rawListeners('log'); const logFnWrapper = listeners[0]; // Logs "log once" to the console and does not unbind the `once` event logFnWrapper.listener(); // Logs "log once" to the console and removes the listener logFnWrapper(); emitter.on('log', () => console.log('log persistently')); // Will return a new Array with a single function bound by `.on()` above const newListeners = emitter.rawListeners('log'); // Logs "log persistently" twice newListeners[0](); emitter.emit('log'); ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">rawListenersE extends keyof SocketEventMap>(eventName: E): (...args: SocketEventMap[E]) => void[];Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

import { EventEmitter } from 'node:events'; const emitter = new EventEmitter(); emitter.once('log', () => console.log('log once')); // Returns a new Array with a function `onceWrapper` which has a property // `listener` which contains the original listener bound above const listeners = emitter.rawListeners('log'); const logFnWrapper = listeners[0]; // Logs "log once" to the console and does not unbind the `once` event logFnWrapper.listener(); // Logs "log once" to the console and removes the listener logFnWrapper(); emitter.on('log', () => console.log('log persistently')); // Will return a new Array with a single function bound by `.on()` above const newListeners = emitter.rawListeners('log'); // Logs "log persistently" twice newListeners[0](); emitter.emit('log'); rawListeners(eventName: string | symbol): (...args: any[]) => void[]; { let chunk; console.log('Stream is readable (new data received in buffer)'); // Use a loop to make sure we read all currently available data while (null !== (chunk = readable.read())) { console.log(`Read ${chunk.length} bytes of data...`); } }); // 'end' will be triggered once when there is no more data available readable.on('end', () => { console.log('Reached end of stream.'); }); ``` Each call to `readable.read()` returns a chunk of data, or `null`. The chunks are not concatenated. A `while` loop is necessary to consume all data currently in the buffer. When reading a large file `.read()` may return `null`, having consumed all buffered content so far, but there is still more data to come not yet buffered. In this case a new `'readable'` event will be emitted when there is more data in the buffer. Finally the `'end'` event will be emitted when there is no more data to come. Therefore to read a file's whole contents from a `readable`, it is necessary to collect chunks across multiple `'readable'` events: ```js const chunks = []; readable.on('readable', () => { let chunk; while (null !== (chunk = readable.read())) { chunks.push(chunk); } }); readable.on('end', () => { const content = chunks.join(''); }); ``` A `Readable` stream in object mode will always return a single item from a call to `readable.read(size)`, regardless of the value of the `size` argument. If the `readable.read()` method returns a chunk of data, a `'data'` event will also be emitted. Calling read after the `'end'` event has been emitted will return `null`. No runtime error will be raised." data-algolia-static="false" data-algolia-merged="false" data-type="Method">read(size?: number): any;The readable.read() method reads data out of the internal buffer and returns it. If no data is available to be read, null is returned. By default, the data is returned as a Buffer object unless an encoding has been specified using the readable.setEncoding() method or the stream is operating in object mode.

The optional size argument specifies a specific number of bytes to read. If size bytes are not available to be read, null will be returned unless the stream has ended, in which case all of the data remaining in the internal buffer will be returned.

If the size argument is not specified, all of the data contained in the internal buffer will be returned.

The size argument must be less than or equal to 1 GiB.

The readable.read() method should only be called on Readable streams operating in paused mode. In flowing mode, readable.read() is called automatically until the internal buffer is fully drained.

const readable = getReadableStreamSomehow(); // 'readable' may be triggered multiple times as data is buffered in readable.on('readable', () => { let chunk; console.log('Stream is readable (new data received in buffer)'); // Use a loop to make sure we read all currently available data while (null !== (chunk = readable.read())) { console.log(`Read ${chunk.length} bytes of data...`); } }); // 'end' will be triggered once when there is no more data available readable.on('end', () => { console.log('Reached end of stream.'); }); Each call to readable.read() returns a chunk of data, or null. The chunks are not concatenated. A while loop is necessary to consume all data currently in the buffer. When reading a large file .read() may return null, having consumed all buffered content so far, but there is still more data to come not yet buffered. In this case a new 'readable' event will be emitted when there is more data in the buffer. Finally the 'end' event will be emitted when there is no more data to come.

Therefore to read a file's whole contents from a readable, it is necessary to collect chunks across multiple 'readable' events:

const chunks = []; readable.on('readable', () => { let chunk; while (null !== (chunk = readable.read())) { chunks.push(chunk); } }); readable.on('end', () => { const content = chunks.join(''); }); A Readable stream in object mode will always return a single item from a call to readable.read(size), regardless of the value of the size argument.

If the readable.read() method returns a chunk of data, a 'data' event will also be emitted.

Calling read after the 'end' event has been emitted will return null. No runtime error will be raised.

@param sizeOptional argument to specify how much data to read.

reduceT>(fn: (previous: any, data: any, options?: Abortable) => T): PromiseT>;This method calls fn on each chunk of the stream in order, passing it the result from the calculation on the previous element. It returns a promise for the final value of the reduction.

If no initial value is supplied the first chunk of the stream is used as the initial value. If the stream is empty, the promise is rejected with a TypeError with the ERR_INVALID_ARGS code property.

The reducer function iterates the stream element-by-element which means that there is no concurrency parameter or parallelism. To perform a reduce concurrently, you can extract the async function to readable.map method.

@param fna reducer function to call over every chunk in the stream. Async or not.

@returnsa promise for the final value of the reduction.

reduceT>(fn: (previous: T, data: any, options?: Abortable) => T,initial: T,options?: Abortable): PromiseT>;This method calls fn on each chunk of the stream in order, passing it the result from the calculation on the previous element. It returns a promise for the final value of the reduction.

If no initial value is supplied the first chunk of the stream is used as the initial value. If the stream is empty, the promise is rejected with a TypeError with the ERR_INVALID_ARGS code property.

The reducer function iterates the stream element-by-element which means that there is no concurrency parameter or parallelism. To perform a reduce concurrently, you can extract the async function to readable.map method.

@param fna reducer function to call over every chunk in the stream. Async or not.

@param initialthe initial value to use in the reduction.

@returnsa promise for the final value of the reduction.

ref(): this;Opposite of unref(), calling ref() on a previously unrefed socket will not let the program exit if it's the only socket left (the default behavior). If the socket is refed calling ref again will have no effect.

@returnsThe socket itself.

removeAllListenersE extends keyof SocketEventMap>(eventName?: E): this;Removes all listeners, or those of the specified eventName.

It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

Returns a reference to the EventEmitter, so that calls can be chained.

removeAllListeners(eventName?: string | symbol): this; { console.log('someone connected!'); }; server.on('connection', callback); // ... server.removeListener('connection', callback); ``` `removeListener()` will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified `eventName`, then `removeListener()` must be called multiple times to remove each instance. Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that any `removeListener()` or `removeAllListeners()` calls _after_ emitting and _before_ the last listener finishes execution will not remove them from `emit()` in progress. Subsequent events behave as expected. ```js import { EventEmitter } from 'node:events'; class MyEmitter extends EventEmitter {} const myEmitter = new MyEmitter(); const callbackA = () => { console.log('A'); myEmitter.removeListener('event', callbackB); }; const callbackB = () => { console.log('B'); }; myEmitter.on('event', callbackA); myEmitter.on('event', callbackB); // callbackA removes listener callbackB but it will still be called. // Internal listener array at time of emit [callbackA, callbackB] myEmitter.emit('event'); // Prints: // A // B // callbackB is now removed. // Internal listener array [callbackA] myEmitter.emit('event'); // Prints: // A ``` Because listeners are managed using an internal array, calling this will change the position indexes of any listener registered _after_ the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the `emitter.listeners()` method will need to be recreated. When a single function has been added as a handler multiple times for a single event (as in the example below), `removeListener()` will remove the most recently added instance. In the example the `once('ping')` listener is removed: ```js import { EventEmitter } from 'node:events'; const ee = new EventEmitter(); function pong() { console.log('pong'); } ee.on('ping', pong); ee.once('ping', pong); ee.removeListener('ping', pong); ee.emit('ping'); ee.emit('ping'); ``` Returns a reference to the `EventEmitter`, so that calls can be chained." data-algolia-static="false" data-algolia-merged="false" data-type="Method">removeListenerE extends keyof SocketEventMap>(eventName: E,listener: (...args: SocketEventMap[E]) => void): this;Removes the specified listener from the listener array for the event named eventName.

const callback = (stream) => { console.log('someone connected!'); }; server.on('connection', callback); // ... server.removeListener('connection', callback); removeListener() will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified eventName, then removeListener() must be called multiple times to remove each instance.

Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that any removeListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them from emit() in progress. Subsequent events behave as expected.

import { EventEmitter } from 'node:events'; class MyEmitter extends EventEmitter {} const myEmitter = new MyEmitter(); const callbackA = () => { console.log('A'); myEmitter.removeListener('event', callbackB); }; const callbackB = () => { console.log('B'); }; myEmitter.on('event', callbackA); myEmitter.on('event', callbackB); // callbackA removes listener callbackB but it will still be called. // Internal listener array at time of emit [callbackA, callbackB] myEmitter.emit('event'); // Prints: // A // B // callbackB is now removed. // Internal listener array [callbackA] myEmitter.emit('event'); // Prints: // A Because listeners are managed using an internal array, calling this will change the position indexes of any listener registered after the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the emitter.listeners() method will need to be recreated.

When a single function has been added as a handler multiple times for a single event (as in the example below), removeListener() will remove the most recently added instance. In the example the once('ping') listener is removed:

import { EventEmitter } from 'node:events'; const ee = new EventEmitter(); function pong() { console.log('pong'); } ee.on('ping', pong); ee.once('ping', pong); ee.removeListener('ping', pong); ee.emit('ping'); ee.emit('ping'); Returns a reference to the EventEmitter, so that calls can be chained.

removeListener(eventName: string | symbol,listener: (...args: any[]) => void): this;resetAndDestroy(): this;Close the TCP connection by sending an RST packet and destroy the stream. If this TCP socket is in connecting status, it will send an RST packet and destroy this TCP socket once it is connected. Otherwise, it will call socket.destroy with an ERR_SOCKET_CLOSED Error. If this is not a TCP socket (for example, a pipe), calling this method will immediately throw an ERR_INVALID_HANDLE_TYPE Error.

resume(): this;Resumes reading after a call to socket.pause().

@returnsThe socket itself.

setDefaultEncoding(encoding: BufferEncoding): this;The writable.setDefaultEncoding() method sets the default encoding for a Writable stream.

@param encodingThe new default encoding

setEncoding(encoding?: BufferEncoding): this;Set the encoding for the socket as a Readable Stream. See readable.setEncoding() for more information.

@returnsThe socket itself.

setKeepAlive(enable?: boolean,initialDelay?: number): this;Enable/disable keep-alive functionality, and optionally set the initial delay before the first keepalive probe is sent on an idle socket.

Set initialDelay (in milliseconds) to set the delay between the last data packet received and the first keepalive probe. Setting 0 forinitialDelay will leave the value unchanged from the default (or previous) setting.

Enabling the keep-alive functionality will set the following socket options:

SO_KEEPALIVE=1TCP_KEEPIDLE=initialDelayTCP_KEEPCNT=10TCP_KEEPINTVL=1@returnsThe socket itself.

setMaxListeners(n: number): this;By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) to indicate an unlimited number of listeners.

Returns a reference to the EventEmitter, so that calls can be chained.

setNoDelay(noDelay?: boolean): this;Enable/disable the use of Nagle's algorithm.

When a TCP connection is created, it will have Nagle's algorithm enabled.

Nagle's algorithm delays data before it is sent via the network. It attempts to optimize throughput at the expense of latency.

Passing true for noDelay or not passing an argument will disable Nagle's algorithm for the socket. Passing false for noDelay will enable Nagle's algorithm.

@returnsThe socket itself.

{ console.log('socket timeout'); socket.end(); }); ``` If `timeout` is 0, then the existing idle timeout is disabled. The optional `callback` parameter will be added as a one-time listener for the `'timeout'` event." data-algolia-static="false" data-algolia-merged="false" data-type="Method">setTimeout(timeout: number,callback?: () => void): this;Sets the socket to timeout after timeout milliseconds of inactivity on the socket. By default net.Socket do not have a timeout.

When an idle timeout is triggered the socket will receive a 'timeout' event but the connection will not be severed. The user must manually call socket.end() or socket.destroy() to end the connection.

socket.setTimeout(3000); socket.on('timeout', () => { console.log('socket timeout'); socket.end(); }); If timeout is 0, then the existing idle timeout is disabled.

The optional callback parameter will be added as a one-time listener for the 'timeout' event.

@returnsThe socket itself.

some(fn: (data: any, options?: Abortable) => boolean | Promiseboolean>,options?: PickReadableOperatorOptions, 'signal' | 'concurrency'>): Promiseboolean>;This method is similar to Array.prototype.some and calls fn on each chunk in the stream until the awaited return value is true (or any truthy value). Once an fn call on a chunk awaited return value is truthy, the stream is destroyed and the promise is fulfilled with true. If none of the fn calls on the chunks return a truthy value, the promise is fulfilled with false.

@param fna function to call on each chunk of the stream. Async or not.

@returnsa promise evaluating to true if fn returned a truthy value for at least one of the chunks.

take(limit: number,options?: Abortable): Readable;This method returns a new stream with the first limit chunks.

@param limitthe number of chunks to take from the readable.

@returnsa stream with limit chunks taken.

toArray(options?: Abortable): Promiseany[]>;This method allows easily obtaining the contents of a stream.

As this method reads the entire stream into memory, it negates the benefits of streams. It's intended for interoperability and convenience, not as the primary way to consume streams.

@returnsa promise containing an array with the contents of the stream.

stream.uncork()); ``` If the `writable.cork()` method is called multiple times on a stream, the same number of calls to `writable.uncork()` must be called to flush the buffered data. ```js stream.cork(); stream.write('some '); stream.cork(); stream.write('data '); process.nextTick(() => { stream.uncork(); // The data will not be flushed until uncork() is called a second time. stream.uncork(); }); ``` See also: `writable.cork()`." data-algolia-static="false" data-algolia-merged="false" data-type="Method">uncork(): void;The writable.uncork() method flushes all data buffered since cork was called.

When using writable.cork() and writable.uncork() to manage the buffering of writes to a stream, defer calls to writable.uncork() using process.nextTick(). Doing so allows batching of all writable.write() calls that occur within a given Node.js event loop phase.

stream.cork(); stream.write('some '); stream.write('data '); process.nextTick(() => stream.uncork()); If the writable.cork() method is called multiple times on a stream, the same number of calls to writable.uncork() must be called to flush the buffered data.

stream.cork(); stream.write('some '); stream.cork(); stream.write('data '); process.nextTick(() => { stream.uncork(); // The data will not be flushed until uncork() is called a second time. stream.uncork(); }); See also: writable.cork().

{ console.log('Stop writing to file.txt.'); readable.unpipe(writable); console.log('Manually close the file stream.'); writable.end(); }, 1000); ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">unpipe(destination?: WritableStream): this;The readable.unpipe() method detaches a Writable stream previously attached using the pipe method.

If the destination is not specified, then all pipes are detached.

If the destination is specified, but no pipe is set up for it, then the method does nothing.

import fs from 'node:fs'; const readable = getReadableStreamSomehow(); const writable = fs.createWriteStream('file.txt'); // All the data from readable goes into 'file.txt', // but only for the first second. readable.pipe(writable); setTimeout(() => { console.log('Stop writing to file.txt.'); readable.unpipe(writable); console.log('Manually close the file stream.'); writable.end(); }, 1000); @param destinationOptional specific stream to unpipe

unref(): this;Calling unref() on a socket will allow the program to exit if this is the only active socket in the event system. If the socket is already unrefed callingunref() again will have no effect.

@returnsThe socket itself.

unshift(chunk: any,encoding?: BufferEncoding): void;Passing chunk as null signals the end of the stream (EOF) and behaves the same as readable.push(null), after which no more data can be written. The EOF signal is put at the end of the buffer and any buffered data will still be flushed.

The readable.unshift() method pushes a chunk of data back into the internal buffer. This is useful in certain situations where a stream is being consumed by code that needs to "un-consume" some amount of data that it has optimistically pulled out of the source, so that the data can be passed on to some other party.

The stream.unshift(chunk) method cannot be called after the 'end' event has been emitted or a runtime error will be thrown.

Developers using stream.unshift() often should consider switching to use of a Transform stream instead. See the API for stream implementers section for more information.

// Pull off a header delimited by \n\n. // Use unshift() if we get too much. // Call the callback with (error, header, stream). import { StringDecoder } from 'node:string_decoder'; function parseHeader(stream, callback) { stream.on('error', callback); stream.on('readable', onReadable); const decoder = new StringDecoder('utf8'); let header = ''; function onReadable() { let chunk; while (null !== (chunk = stream.read())) { const str = decoder.write(chunk); if (str.includes('\n\n')) { // Found the header boundary. const split = str.split(/\n\n/); header += split.shift(); const remaining = split.join('\n\n'); const buf = Buffer.from(remaining, 'utf8'); stream.removeListener('error', callback); // Remove the 'readable' listener before unshifting. stream.removeListener('readable', onReadable); if (buf.length) stream.unshift(buf); // Now the body of the message can be read from the stream. callback(null, header, stream); return; } // Still reading the header. header += str; } } } Unlike push, stream.unshift(chunk) will not end the reading process by resetting the internal reading state of the stream. This can cause unexpected results if readable.unshift() is called during a read (i.e. from within a _read implementation on a custom stream). Following the call to readable.unshift() with an immediate push will reset the reading state appropriately, however it is best to simply avoid calling readable.unshift() while in the process of performing a read.

@param chunkChunk of data to unshift onto the read queue. For streams not operating in object mode, chunk must be a {string}, {Buffer}, {TypedArray}, {DataView} or null. For object mode streams, chunk may be any JavaScript value.

@param encodingEncoding of string chunks. Must be a valid Buffer encoding, such as 'utf8' or 'ascii'.

{ myReader.read(); // etc. }); ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">wrap(stream: ReadableStream): this;Prior to Node.js 0.10, streams did not implement the entire node:stream module API as it is currently defined. (See Compatibility for more information.)

When using an older Node.js library that emits 'data' events and has a pause method that is advisory only, the readable.wrap() method can be used to create a Readable stream that uses the old stream as its data source.

It will rarely be necessary to use readable.wrap() but the method has been provided as a convenience for interacting with older Node.js applications and libraries.

import { OldReader } from './old-api-module.js'; import { Readable } from 'node:stream'; const oreader = new OldReader(); const myReader = new Readable().wrap(oreader); myReader.on('readable', () => { myReader.read(); // etc. }); @param streamAn "old style" readable stream

write(buffer: string | Uint8ArrayArrayBufferLike>,cb?: (err?: null | Error) => void): boolean;Sends data on the socket. The second parameter specifies the encoding in the case of a string. It defaults to UTF8 encoding.

Returns true if the entire data was flushed successfully to the kernel buffer. Returns false if all or part of the data was queued in user memory.'drain' will be emitted when the buffer is again free.

The optional callback parameter will be executed when the data is finally written out, which may not be immediately.

See Writable stream write() method for more information.

write(str: string | Uint8ArrayArrayBufferLike>,encoding?: BufferEncoding,cb?: (err?: null | Error) => void): boolean;Sends data on the socket. The second parameter specifies the encoding in the case of a string. It defaults to UTF8 encoding.

Returns true if the entire data was flushed successfully to the kernel buffer. Returns false if all or part of the data was queued in user memory.'drain' will be emitted when the buffer is again free.

The optional callback parameter will be executed when the data is finally written out, which may not be immediately.

See Writable stream write() method for more information.

@param encodingOnly used when data is string.

static from(src: string | Blob | Promiseany> | ReadableStream | WritableStream | Iterableany, any, any> | AsyncIterableany, any, any> | (source: AsyncIterableany>) => AsyncIterableany> | (source: AsyncIterableany>) => Promisevoid> | ReadableWritablePairany, any> | ReadableStreamany> | WritableStreamany>): Duplex;A utility method for creating duplex streams.

Stream converts writable stream into writable Duplex and readable stream to Duplex.Blob converts into readable Duplex.string converts into readable Duplex.ArrayBuffer converts into readable Duplex.AsyncIterable converts into a readable Duplex. Cannot yield null.AsyncGeneratorFunction converts into a readable/writable transform Duplex. Must take a source AsyncIterable as first parameter. Cannot yield null.AsyncFunction converts into a writable Duplex. Must return either null or undefinedObject ({ writable, readable }) converts readable and writable into Stream and then combines them into Duplex where the Duplex will write to the writable and read from the readable.Promise converts into readable Duplex. Value null is ignored.static fromWeb(duplexStream: ReadableWritablePair,options?: PickDuplexOptionsDuplex>, 'signal' | 'allowHalfOpen' | 'decodeStrings' | 'encoding' | 'highWaterMark' | 'objectMode'>): Duplex;A utility method for creating a Duplex from a web ReadableStream and WritableStream.

static toWeb(streamDuplex: ReadWriteStream): ReadableWritablePair;A utility method for creating a web ReadableStream and WritableStream from a Duplex.

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