ReadonlylisteningSet this property to reject connections when the server's connection count gets high.
It is not recommended to use this option once a socket has been sent to a child
with child_process.fork().
Calls Server.close() and returns a promise that fulfills when the server has closed.
Optional[captureevents.EventEmitter
events.EventEmitter
events.EventEmitter
events.EventEmitter
events.EventEmitter
events.EventEmitter
Returns the bound address, the address family name, and port of the server
as reported by the operating system if listening on an IP socket
(useful to find which port was assigned when getting an OS-assigned address):{ port: 12346, family: 'IPv4', address: '127.0.0.1' }.
For a server listening on a pipe or Unix domain socket, the name is returned as a string.
const server = net.createServer((socket) => {
socket.end('goodbye\n');
}).on('error', (err) => {
// Handle errors here.
throw err;
});
// Grab an arbitrary unused port.
server.listen(() => {
console.log('opened server on', server.address());
});
server.address() returns null before the 'listening' event has been
emitted or after calling server.close().
Stops the server from accepting new connections and keeps existing
connections. This function is asynchronous, the server is finally closed
when all connections are ended and the server emits a 'close' event.
The optional callback will be called once the 'close' event occurs. Unlike
that event, it will be called with an Error as its only argument if the server
was not open when it was closed.
Optionalcallback: (err?: Error) => voidCalled when the server is closed.
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
Optionaldata: DropArgumentReturns an array listing the events for which the emitter has registered
listeners. The values in the array are strings or Symbols.
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) ]
Returns the current max listener value for the EventEmitter which is either
set by emitter.setMaxListeners(n) or defaults to EventEmitter.defaultMaxListeners.
Start a server listening for connections. A net.Server can be a TCP or
an IPC server depending on what it listens to.
Possible signatures:
server.listen(handle[, backlog][, callback])server.listen(options[, callback])server.listen(path[, backlog][, callback]) for IPC serversserver.listen([port[, host[, backlog]]][, callback]) for TCP serversThis function is asynchronous. When the server starts listening, the 'listening' event will be emitted. The last parameter callbackwill be added as a listener for the 'listening'
event.
All listen() methods can take a backlog parameter to specify the maximum
length of the queue of pending connections. The actual length will be determined
by the OS through sysctl settings such as tcp_max_syn_backlog and somaxconn on Linux. The default value of this parameter is 511 (not 512).
All Socket are set to SO_REUSEADDR (see socket(7) for
details).
The server.listen() method can be called again if and only if there was an
error during the first server.listen() call or server.close() has been
called. Otherwise, an ERR_SERVER_ALREADY_LISTEN error will be thrown.
One of the most common errors raised when listening is EADDRINUSE.
This happens when another server is already listening on the requestedport/path/handle. One way to handle this would be to retry
after a certain amount of time:
server.on('error', (e) => {
if (e.code === 'EADDRINUSE') {
console.error('Address in use, retrying...');
setTimeout(() => {
server.close();
server.listen(PORT, HOST);
}, 1000);
}
});
Optionalport: numberOptionalhostname: stringOptionalbacklog: numberOptionallisteningListener: () => voidStart a server listening for connections. A net.Server can be a TCP or
an IPC server depending on what it listens to.
Possible signatures:
server.listen(handle[, backlog][, callback])server.listen(options[, callback])server.listen(path[, backlog][, callback]) for IPC serversserver.listen([port[, host[, backlog]]][, callback]) for TCP serversThis function is asynchronous. When the server starts listening, the 'listening' event will be emitted. The last parameter callbackwill be added as a listener for the 'listening'
event.
All listen() methods can take a backlog parameter to specify the maximum
length of the queue of pending connections. The actual length will be determined
by the OS through sysctl settings such as tcp_max_syn_backlog and somaxconn on Linux. The default value of this parameter is 511 (not 512).
All Socket are set to SO_REUSEADDR (see socket(7) for
details).
The server.listen() method can be called again if and only if there was an
error during the first server.listen() call or server.close() has been
called. Otherwise, an ERR_SERVER_ALREADY_LISTEN error will be thrown.
One of the most common errors raised when listening is EADDRINUSE.
This happens when another server is already listening on the requestedport/path/handle. One way to handle this would be to retry
after a certain amount of time:
server.on('error', (e) => {
if (e.code === 'EADDRINUSE') {
console.error('Address in use, retrying...');
setTimeout(() => {
server.close();
server.listen(PORT, HOST);
}, 1000);
}
});
Optionalport: numberOptionalhostname: stringOptionallisteningListener: () => voidStart a server listening for connections. A net.Server can be a TCP or
an IPC server depending on what it listens to.
Possible signatures:
server.listen(handle[, backlog][, callback])server.listen(options[, callback])server.listen(path[, backlog][, callback]) for IPC serversserver.listen([port[, host[, backlog]]][, callback]) for TCP serversThis function is asynchronous. When the server starts listening, the 'listening' event will be emitted. The last parameter callbackwill be added as a listener for the 'listening'
event.
All listen() methods can take a backlog parameter to specify the maximum
length of the queue of pending connections. The actual length will be determined
by the OS through sysctl settings such as tcp_max_syn_backlog and somaxconn on Linux. The default value of this parameter is 511 (not 512).
All Socket are set to SO_REUSEADDR (see socket(7) for
details).
The server.listen() method can be called again if and only if there was an
error during the first server.listen() call or server.close() has been
called. Otherwise, an ERR_SERVER_ALREADY_LISTEN error will be thrown.
One of the most common errors raised when listening is EADDRINUSE.
This happens when another server is already listening on the requestedport/path/handle. One way to handle this would be to retry
after a certain amount of time:
server.on('error', (e) => {
if (e.code === 'EADDRINUSE') {
console.error('Address in use, retrying...');
setTimeout(() => {
server.close();
server.listen(PORT, HOST);
}, 1000);
}
});
Optionalport: numberOptionalbacklog: numberOptionallisteningListener: () => voidStart a server listening for connections. A net.Server can be a TCP or
an IPC server depending on what it listens to.
Possible signatures:
server.listen(handle[, backlog][, callback])server.listen(options[, callback])server.listen(path[, backlog][, callback]) for IPC serversserver.listen([port[, host[, backlog]]][, callback]) for TCP serversThis function is asynchronous. When the server starts listening, the 'listening' event will be emitted. The last parameter callbackwill be added as a listener for the 'listening'
event.
All listen() methods can take a backlog parameter to specify the maximum
length of the queue of pending connections. The actual length will be determined
by the OS through sysctl settings such as tcp_max_syn_backlog and somaxconn on Linux. The default value of this parameter is 511 (not 512).
All Socket are set to SO_REUSEADDR (see socket(7) for
details).
The server.listen() method can be called again if and only if there was an
error during the first server.listen() call or server.close() has been
called. Otherwise, an ERR_SERVER_ALREADY_LISTEN error will be thrown.
One of the most common errors raised when listening is EADDRINUSE.
This happens when another server is already listening on the requestedport/path/handle. One way to handle this would be to retry
after a certain amount of time:
server.on('error', (e) => {
if (e.code === 'EADDRINUSE') {
console.error('Address in use, retrying...');
setTimeout(() => {
server.close();
server.listen(PORT, HOST);
}, 1000);
}
});
Optionalport: numberOptionallisteningListener: () => voidStart a server listening for connections. A net.Server can be a TCP or
an IPC server depending on what it listens to.
Possible signatures:
server.listen(handle[, backlog][, callback])server.listen(options[, callback])server.listen(path[, backlog][, callback]) for IPC serversserver.listen([port[, host[, backlog]]][, callback]) for TCP serversThis function is asynchronous. When the server starts listening, the 'listening' event will be emitted. The last parameter callbackwill be added as a listener for the 'listening'
event.
All listen() methods can take a backlog parameter to specify the maximum
length of the queue of pending connections. The actual length will be determined
by the OS through sysctl settings such as tcp_max_syn_backlog and somaxconn on Linux. The default value of this parameter is 511 (not 512).
All Socket are set to SO_REUSEADDR (see socket(7) for
details).
The server.listen() method can be called again if and only if there was an
error during the first server.listen() call or server.close() has been
called. Otherwise, an ERR_SERVER_ALREADY_LISTEN error will be thrown.
One of the most common errors raised when listening is EADDRINUSE.
This happens when another server is already listening on the requestedport/path/handle. One way to handle this would be to retry
after a certain amount of time:
server.on('error', (e) => {
if (e.code === 'EADDRINUSE') {
console.error('Address in use, retrying...');
setTimeout(() => {
server.close();
server.listen(PORT, HOST);
}, 1000);
}
});
Optionalbacklog: numberOptionallisteningListener: () => voidStart a server listening for connections. A net.Server can be a TCP or
an IPC server depending on what it listens to.
Possible signatures:
server.listen(handle[, backlog][, callback])server.listen(options[, callback])server.listen(path[, backlog][, callback]) for IPC serversserver.listen([port[, host[, backlog]]][, callback]) for TCP serversThis function is asynchronous. When the server starts listening, the 'listening' event will be emitted. The last parameter callbackwill be added as a listener for the 'listening'
event.
All listen() methods can take a backlog parameter to specify the maximum
length of the queue of pending connections. The actual length will be determined
by the OS through sysctl settings such as tcp_max_syn_backlog and somaxconn on Linux. The default value of this parameter is 511 (not 512).
All Socket are set to SO_REUSEADDR (see socket(7) for
details).
The server.listen() method can be called again if and only if there was an
error during the first server.listen() call or server.close() has been
called. Otherwise, an ERR_SERVER_ALREADY_LISTEN error will be thrown.
One of the most common errors raised when listening is EADDRINUSE.
This happens when another server is already listening on the requestedport/path/handle. One way to handle this would be to retry
after a certain amount of time:
server.on('error', (e) => {
if (e.code === 'EADDRINUSE') {
console.error('Address in use, retrying...');
setTimeout(() => {
server.close();
server.listen(PORT, HOST);
}, 1000);
}
});
OptionallisteningListener: () => voidStart a server listening for connections. A net.Server can be a TCP or
an IPC server depending on what it listens to.
Possible signatures:
server.listen(handle[, backlog][, callback])server.listen(options[, callback])server.listen(path[, backlog][, callback]) for IPC serversserver.listen([port[, host[, backlog]]][, callback]) for TCP serversThis function is asynchronous. When the server starts listening, the 'listening' event will be emitted. The last parameter callbackwill be added as a listener for the 'listening'
event.
All listen() methods can take a backlog parameter to specify the maximum
length of the queue of pending connections. The actual length will be determined
by the OS through sysctl settings such as tcp_max_syn_backlog and somaxconn on Linux. The default value of this parameter is 511 (not 512).
All Socket are set to SO_REUSEADDR (see socket(7) for
details).
The server.listen() method can be called again if and only if there was an
error during the first server.listen() call or server.close() has been
called. Otherwise, an ERR_SERVER_ALREADY_LISTEN error will be thrown.
One of the most common errors raised when listening is EADDRINUSE.
This happens when another server is already listening on the requestedport/path/handle. One way to handle this would be to retry
after a certain amount of time:
server.on('error', (e) => {
if (e.code === 'EADDRINUSE') {
console.error('Address in use, retrying...');
setTimeout(() => {
server.close();
server.listen(PORT, HOST);
}, 1000);
}
});
OptionallisteningListener: () => voidStart a server listening for connections. A net.Server can be a TCP or
an IPC server depending on what it listens to.
Possible signatures:
server.listen(handle[, backlog][, callback])server.listen(options[, callback])server.listen(path[, backlog][, callback]) for IPC serversserver.listen([port[, host[, backlog]]][, callback]) for TCP serversThis function is asynchronous. When the server starts listening, the 'listening' event will be emitted. The last parameter callbackwill be added as a listener for the 'listening'
event.
All listen() methods can take a backlog parameter to specify the maximum
length of the queue of pending connections. The actual length will be determined
by the OS through sysctl settings such as tcp_max_syn_backlog and somaxconn on Linux. The default value of this parameter is 511 (not 512).
All Socket are set to SO_REUSEADDR (see socket(7) for
details).
The server.listen() method can be called again if and only if there was an
error during the first server.listen() call or server.close() has been
called. Otherwise, an ERR_SERVER_ALREADY_LISTEN error will be thrown.
One of the most common errors raised when listening is EADDRINUSE.
This happens when another server is already listening on the requestedport/path/handle. One way to handle this would be to retry
after a certain amount of time:
server.on('error', (e) => {
if (e.code === 'EADDRINUSE') {
console.error('Address in use, retrying...');
setTimeout(() => {
server.close();
server.listen(PORT, HOST);
}, 1000);
}
});
Optionalbacklog: numberOptionallisteningListener: () => voidStart a server listening for connections. A net.Server can be a TCP or
an IPC server depending on what it listens to.
Possible signatures:
server.listen(handle[, backlog][, callback])server.listen(options[, callback])server.listen(path[, backlog][, callback]) for IPC serversserver.listen([port[, host[, backlog]]][, callback]) for TCP serversThis function is asynchronous. When the server starts listening, the 'listening' event will be emitted. The last parameter callbackwill be added as a listener for the 'listening'
event.
All listen() methods can take a backlog parameter to specify the maximum
length of the queue of pending connections. The actual length will be determined
by the OS through sysctl settings such as tcp_max_syn_backlog and somaxconn on Linux. The default value of this parameter is 511 (not 512).
All Socket are set to SO_REUSEADDR (see socket(7) for
details).
The server.listen() method can be called again if and only if there was an
error during the first server.listen() call or server.close() has been
called. Otherwise, an ERR_SERVER_ALREADY_LISTEN error will be thrown.
One of the most common errors raised when listening is EADDRINUSE.
This happens when another server is already listening on the requestedport/path/handle. One way to handle this would be to retry
after a certain amount of time:
server.on('error', (e) => {
if (e.code === 'EADDRINUSE') {
console.error('Address in use, retrying...');
setTimeout(() => {
server.close();
server.listen(PORT, HOST);
}, 1000);
}
});
OptionallisteningListener: () => voidReturns 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.
The name of the event being listened for
Optionallistener: FunctionThe event handler function
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] ]
Alias for emitter.removeListener().
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
The callback function
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
The callback function
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.
The callback function
Adds a one-timelistener 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.
The callback function
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');
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.
OptionaleventName: string | symbolRemoves 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 fromemit() 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 indices 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.
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.
Indicates whether or not the server is listening for connections.