v0.9.4
Readonly bufferThis property shows the number of characters buffered for writing. The buffer may contain strings whose length after encoding is not yet known. So this number is only an approximation of the number of bytes in the buffer.
net.Socket has the property that socket.write() always works. This is to
help users get up and running quickly. The computer cannot always keep up
with the amount of data that is written to a socket. The network connection
simply might be too slow. Node.js will internally queue up the data written to a
socket and send it out over the wire when it is possible.
The consequence of this internal buffering is that memory may grow.
Users who experience large or growing bufferSize should attempt to
"throttle" the data flows in their program with socket.pause() and socket.resume().
v0.3.8
Since v14.6.0 - Use writableLength instead.
Readonly bytesThe amount of received bytes.
v0.5.3
Readonly bytesThe amount of bytes sent.
v0.5.3
Readonly closedReadonly connectingIf 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.
v6.1.0
Readonly destroyedSee writable.destroyed for further details.
Readonly erroredA boolean that is true if the TTY is currently configured to operate as a
raw device. Defaults to false.
v0.7.7
A boolean that is always true for tty.ReadStream instances.
v0.5.8
Optional Readonly localThe 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'.
v0.9.6
Optional Readonly localThe string representation of the local IP family. 'IPv4' or 'IPv6'.
v18.8.0
Optional Readonly localThe numeric representation of the local port. For example, 80 or 21.
v0.9.6
Readonly pendingThis 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).
v10.16.0
Is true if it is safe to call readable.read(), which means
the stream has not been destroyed or emitted 'error' or 'end'.
v11.4.0
Readonly Experimental readableReturns whether the stream was destroyed or errored before emitting 'end'.
v16.8.0
Readonly Experimental readableReturns whether 'data' has been emitted.
v16.7.0, v14.18.0
Readonly readableGetter for the property encoding of a given Readable stream. The encodingproperty can be set using the readable.setEncoding() method.
v12.7.0
Readonly readableBecomes true when 'end' event is emitted.
v12.9.0
Readonly readableThis property reflects the current state of a Readable stream as described
in the Three states section.
v9.4.0
Readonly readableReturns the value of highWaterMark passed when creating this Readable.
v9.3.0
Readonly readableThis 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.
v9.4.0
Readonly readableGetter for the property objectMode of a given Readable stream.
v12.3.0
Readonly readyThis property represents the state of the connection as a string.
v0.5.0
Optional Readonly remoteThe 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).
v0.5.10
Optional Readonly remoteThe string representation of the remote IP family. 'IPv4' or 'IPv6'.
v0.11.14
Optional Readonly remoteThe numeric representation of the remote port. For example, 80 or 21.
v0.5.10
Optional Readonly timeoutThe socket timeout in milliseconds as set by socket.setTimeout(). It is undefined if a timeout has not been set.
v10.7.0
Readonly writableReadonly writableReadonly writableReadonly writableReadonly writableReadonly writableReadonly writableReadonly writableOptional [captureOptional _constructOptional _writevevents.EventEmitter
Rest ...args: any[]This method returns a new stream with chunks of the underlying stream paired with a counter
in the form [index, chunk]. The first index value is 0 and it increases by 1 for each chunk produced.
Optional options: Pick<ArrayOptions, "signal">a stream of indexed pairs.
v17.5.0
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.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.
Optional connectionListener: (() => void)Optional connectionListener: (() => void)Optional connectionListener: (() => void)Optional connectionListener: (() => void)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().
Optional error: ErrorError which will be passed as payload in 'error' event
v8.0.0
This method returns a new stream with the first limit chunks dropped from the start.
the number of chunks to drop from the readable.
Optional options: Pick<ArrayOptions, "signal">a stream with limit chunks dropped from the start.
v17.5.0
Rest ...args: any[]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.
Optional callback: (() => void)Optional callback for when the socket is finished.
The socket itself.
v0.1.90
Optional callback: (() => void)Optional encoding: BufferEncodingOptional callback: (() => void)Returns an array listing the events for which the emitter has registered
listeners. The values in the array are strings or Symbols.
const EventEmitter = require('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) ]
v6.0.0
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.
a function to call on each chunk of the stream. Async or not.
Optional options: Pick<ArrayOptions, "signal">Optional options: ArrayOptionsa promise evaluating to true if fn returned a truthy value for every one of the chunks.
v17.5.0
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.
a function to filter chunks from the stream. Async or not.
Optional options: Pick<ArrayOptions, "signal">Optional options: ArrayOptionsa stream filtered with the predicate fn.
v17.4.0, v16.14.0
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.
a function to call on each chunk of the stream. Async or not.
Optional options: Pick<ArrayOptions, "signal">Optional options: ArrayOptionsa promise evaluating to the first chunk for which fn evaluated with a truthy value,
or undefined if no element was found.
v17.5.0
Optional options: Pick<ArrayOptions, "signal">Optional options: ArrayOptionsThis 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.
a function to map over every chunk in the stream. May be async. May be a stream or generator.
Optional options: Pick<ArrayOptions, "signal">Optional options: ArrayOptionsa stream flat-mapped with the function fn.
v17.5.0
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.
a function to call on each chunk of the stream. Async or not.
Optional options: Pick<ArrayOptions, "signal">Optional options: ArrayOptionsa promise for when the stream has finished.
v17.5.0
The readable.isPaused() method returns the current operating state of theReadable. This is used primarily by the mechanism that underlies thereadable.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
v0.11.14
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.
Optional options: { Optional destroyWhen set to false, calling return on the async iterator,
or exiting a for await...of iteration using a break, return, or throw will not destroy the stream.
Default: true.
v16.3.0
Returns the number of listeners listening to 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.
The name of the event being listened for
Optional listener: FunctionThe event handler function
v3.2.0
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] ]
v0.1.26
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.
a function to map over every chunk in the stream. Async or not.
Optional options: Pick<ArrayOptions, "signal">Optional options: ArrayOptionsa stream mapped with the function fn.
v17.4.0, v16.14.0
Alias for emitter.removeListener().
Rest ...args: any[]v10.0.0
Rest ...args: any[]Rest ...args: any[]Pauses the reading of data. That is, 'data' events will not be emitted.
Useful to throttle back an upload.
The socket itself.
Rest ...args: any[]Rest ...args: any[]Returns a copy of the array of listeners for the event named eventName,
including any wrappers (such as those created by .once()).
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');
v9.4.0
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. Ifsize 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 thesize 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.
Optional size: numberOptional argument to specify how much data to read.
v0.9.4
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.
a reducer function to call over every chunk in the stream. Async or not.
Optional options: Pick<ArrayOptions, "signal">Optional initial: undefinedthe initial value to use in the reduction.
Optional options: Pick<ArrayOptions, "signal">a promise for the final value of the reduction.
v17.5.0
Optional options: Pick<ArrayOptions, "signal">Optional options: Pick<ArrayOptions, "signal">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.
The socket itself.
v0.9.1
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.
Optional event: string | symbolv0.1.26
Rest ...args: any[]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.
The socket itself.
v18.3.0
Resumes reading after a call to socket.pause().
The socket itself.
Set the encoding for the socket as a Readable Stream. See readable.setEncoding() for more information.
Optional encoding: BufferEncodingThe socket itself.
v0.1.90
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=1Optional enable: booleanOptional initialDelay: numberThe socket itself.
v0.1.92
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 toInfinity (or 0) to indicate an unlimited number of listeners.
Returns a reference to the EventEmitter, so that calls can be chained.
v0.3.5
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.
Optional noDelay: booleanThe socket itself.
v0.1.90
Allows configuration of tty.ReadStream so that it operates as a raw device.
When in raw mode, input is always available character-by-character, not
including modifiers. Additionally, all special processing of characters by the
terminal is disabled, including echoing input
characters. Ctrl+C will no longer cause a SIGINT when
in this mode.
If true, configures the tty.ReadStream to operate as a raw device. If false, configures the tty.ReadStream to operate in its default mode. The readStream.isRaw
property will be set to the resulting mode.
The read stream instance.
v0.7.7
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.
Optional callback: (() => void)The socket itself.
v0.1.90
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.
a function to call on each chunk of the stream. Async or not.
Optional options: Pick<ArrayOptions, "signal">Optional options: ArrayOptionsa promise evaluating to true if fn returned a truthy value for at least one of the chunks.
v17.5.0
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.
Optional options: Pick<ArrayOptions, "signal">a promise containing an array with the contents of the stream.
v17.5.0
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.
const fs = require('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);
Optional destination: WritableStreamOptional specific stream to unpipe
v0.9.4
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.
The socket itself.
v0.9.1
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).
const { StringDecoder } = require('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.
Chunk of data to unshift onto the read queue. For streams not operating in object mode, chunk must be a string, Buffer, Uint8Array or null. For object mode
streams, chunk may be any JavaScript value.
Optional encoding: BufferEncodingEncoding of string chunks. Must be a valid Buffer encoding, such as 'utf8' or 'ascii'.
v0.9.11
Prior to Node.js 0.10, streams did not implement the entire 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, thereadable.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.
const { OldReader } = require('./old-api-module.js');
const { Readable } = require('stream');
const oreader = new OldReader();
const myReader = new Readable().wrap(oreader);
myReader.on('readable', () => {
myReader.read(); // etc.
});
An "old style" readable stream
v0.9.4
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.
Optional cb: ((err?) => void)Optional err: Errorv0.1.90
Optional encoding: BufferEncodingOptional cb: ((err?) => void)Optional err: ErrorGenerated using TypeDoc
If
falsethen the stream will automatically end the writable side when the readable side ends. Set initially by theallowHalfOpenconstructor option, which defaults tofalse.This can be changed manually to change the half-open behavior of an existing
Duplexstream instance, but must be changed before the'end'event is emitted.