function

http.createServer

function createServer<Request extends typeof IncomingMessage = typeof IncomingMessage, Response extends typeof ServerResponse = typeof ServerResponse>(
requestListener?: RequestListener<Request, Response>
): Server<Request, Response>;

Returns a new instance of Server.

The requestListener is a function which is automatically added to the 'request' event.

import http from 'node:http';

// Create a local server to receive data from
const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify({
    data: 'Hello World!',
  }));
});

server.listen(8000);
import http from 'node:http';

// Create a local server to receive data from
const server = http.createServer();

// Listen to the request event
server.on('request', (request, res) => {
  res.writeHead(200, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify({
    data: 'Hello World!',
  }));
});

server.listen(8000);
function createServer<Request extends typeof IncomingMessage = typeof IncomingMessage, Response extends typeof ServerResponse = typeof ServerResponse>(
options: ServerOptions<Request, Response>,
requestListener?: RequestListener<Request, Response>
): Server<Request, Response>;

Returns a new instance of Server.

The requestListener is a function which is automatically added to the 'request' event.

import http from 'node:http';

// Create a local server to receive data from
const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify({
    data: 'Hello World!',
  }));
});

server.listen(8000);
import http from 'node:http';

// Create a local server to receive data from
const server = http.createServer();

// Listen to the request event
server.on('request', (request, res) => {
  res.writeHead(200, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify({
    data: 'Hello World!',
  }));
});

server.listen(8000);

Referenced types

type RequestListener<Request extends typeof IncomingMessage = typeof IncomingMessage, Response extends typeof ServerResponse = typeof ServerResponse> = (request: InstanceType<Request>, response: InstanceType<Response> & { req: InstanceType<Request> }) => void

class Request

This Fetch API interface represents a resource request.

MDN Reference

  • readonly body: null | ReadableStream<Uint8Array<ArrayBufferLike>>
  • readonly bodyUsed: boolean
  • readonly cache: RequestCache

    Returns the cache mode associated with request, which is a string indicating how the request will interact with the browser's cache when fetching.

    MDN Reference

  • readonly credentials: RequestCredentials

    Returns the credentials mode associated with request, which is a string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL.

    MDN Reference

  • readonly destination: RequestDestination

    Returns the kind of resource requested by request, e.g., "document" or "script".

    MDN Reference

  • readonly headers: Headers

    Returns a Headers object consisting of the headers associated with request. Note that headers added in the network layer by the user agent will not be accounted for in this object, e.g., the "Host" header.

    MDN Reference

  • readonly integrity: string

    Returns request's subresource integrity metadata, which is a cryptographic hash of the resource being fetched. Its value consists of multiple hashes separated by whitespace. [SRI]

    MDN Reference

  • readonly keepalive: boolean

    Returns a boolean indicating whether or not request can outlive the global in which it was created.

    MDN Reference

  • readonly method: string

    Returns request's HTTP method, which is "GET" by default.

    MDN Reference

  • readonly mode: RequestMode

    Returns the mode associated with request, which is a string indicating whether the request will use CORS, or will be restricted to same-origin URLs.

    MDN Reference

  • readonly redirect: RequestRedirect

    Returns the redirect mode associated with request, which is a string indicating how redirects for the request will be handled during fetching. A request will follow redirects by default.

    MDN Reference

  • readonly referrer: string

    Returns the referrer of request. Its value can be a same-origin URL if explicitly set in init, the empty string to indicate no referrer, and "about:client" when defaulting to the global's default. This is used during fetching to determine the value of the Referer header of the request being made.

    MDN Reference

  • readonly referrerPolicy: ReferrerPolicy

    Returns the referrer policy associated with request. This is used during fetching to compute the value of the request's referrer.

    MDN Reference

  • readonly signal: AbortSignal

    Returns the signal associated with request, which is an AbortSignal object indicating whether or not request has been aborted, and its abort event handler.

    MDN Reference

  • readonly url: string
  • blob(): Promise<Blob>;
  • bytes(): Promise<Uint8Array<ArrayBufferLike>>;
  • json(): Promise<any>;
  • text(): Promise<string>;

class Response

This Fetch API interface represents the response to a request.

MDN Reference

class Server<Request extends typeof IncomingMessage = typeof IncomingMessage, Response extends typeof ServerResponse = typeof ServerResponse>

  • connections: number
  • headersTimeout: number

    Limit the amount of time the parser will wait to receive the complete HTTP headers.

    If the timeout expires, the server responds with status 408 without forwarding the request to the request listener and then closes the connection.

    It must be set to a non-zero value (e.g. 120 seconds) to protect against potential Denial-of-Service attacks in case the server is deployed without a reverse proxy in front.

  • keepAliveTimeout: number

    The number of milliseconds of inactivity a server needs to wait for additional incoming data, after it has finished writing the last response, before a socket will be destroyed.

    This timeout value is combined with the server.keepAliveTimeoutBuffer option to determine the actual socket timeout, calculated as: socketTimeout = keepAliveTimeout + keepAliveTimeoutBuffer If the server receives new data before the keep-alive timeout has fired, it will reset the regular inactivity timeout, i.e., server.timeout.

    A value of 0 will disable the keep-alive timeout behavior on incoming connections. A value of 0 makes the HTTP server behave similarly to Node.js versions prior to 8.0.0, which did not have a keep-alive timeout.

    The socket timeout logic is set up on connection, so changing this value only affects new connections to the server, not any existing connections.

  • keepAliveTimeoutBuffer: number

    An additional buffer time added to the server.keepAliveTimeout to extend the internal socket timeout.

    This buffer helps reduce connection reset (ECONNRESET) errors by increasing the socket timeout slightly beyond the advertised keep-alive timeout.

    This option applies only to new incoming connections.

  • readonly listening: boolean

    Indicates whether or not the server is listening for connections.

  • maxConnections: number

    Set 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().

  • maxHeadersCount: null | number

    Limits maximum incoming headers count. If set to 0, no limit will be applied.

  • maxRequestsPerSocket: null | number

    The maximum number of requests socket can handle before closing keep alive connection.

    A value of 0 will disable the limit.

    When the limit is reached it will set the Connection header value to close, but will not actually close the connection, subsequent requests sent after the limit is reached will get 503 Service Unavailable as a response.

  • requestTimeout: number

    Sets the timeout value in milliseconds for receiving the entire request from the client.

    If the timeout expires, the server responds with status 408 without forwarding the request to the request listener and then closes the connection.

    It must be set to a non-zero value (e.g. 120 seconds) to protect against potential Denial-of-Service attacks in case the server is deployed without a reverse proxy in front.

  • timeout: number

    The number of milliseconds of inactivity before a socket is presumed to have timed out.

    A value of 0 will disable the timeout behavior on incoming connections.

    The socket timeout logic is set up on connection, so changing this value only affects new connections to the server, not any existing connections.

  • [Symbol.asyncDispose](): Promise<void>;

    Calls () and returns a promise that fulfills when the server has closed.

  • 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.
  }
}
  • addListener<E extends keyof ServerEventMap<typeof IncomingMessage, typeof ServerResponse>>(
    eventName: E,
    listener: (...args: ServerEventMap<Request, Response>[E]) => void
    ): this;

    Alias for emitter.on(eventName, listener).

    eventName: string | symbol,
    listener: (...args: any[]) => void
    ): this;

    Alias for emitter.on(eventName, listener).

  • address(): null | string | AddressInfo;

    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().

  • callback?: (err?: Error) => void
    ): this;

    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.

    @param callback

    Called when the server is closed.

  • Closes all connections connected to this server.

  • Closes all connections connected to this server which are not sending a request or waiting for a response.

  • emit<E extends keyof ServerEventMap<typeof IncomingMessage, typeof ServerResponse>>(
    eventName: E,
    ...args: ServerEventMap<Request, Response>[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
    eventName: string | symbol,
    ...args: any[]
    ): 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
  • 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) ]
  • cb: (error: null | Error, count: number) => void
    ): this;

    Asynchronously get the number of concurrent connections on the server. Works when sockets were sent to forks.

    Callback should take two arguments err and count.

  • getMaxListeners(): number;

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

  • port?: number,
    hostname?: string,
    backlog?: number,
    listeningListener?: () => void
    ): this;

    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 servers
    • server.listen([port[, host[, backlog]]][, callback]) for TCP servers

    This 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);
  }
});
    port?: number,
    hostname?: string,
    listeningListener?: () => void
    ): this;

    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 servers
    • server.listen([port[, host[, backlog]]][, callback]) for TCP servers

    This 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);
  }
});
    port?: number,
    backlog?: number,
    listeningListener?: () => void
    ): this;

    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 servers
    • server.listen([port[, host[, backlog]]][, callback]) for TCP servers

    This 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);
  }
});
    port?: number,
    listeningListener?: () => void
    ): this;

    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 servers
    • server.listen([port[, host[, backlog]]][, callback]) for TCP servers

    This 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);
  }
});
    path: string,
    backlog?: number,
    listeningListener?: () => void
    ): this;

    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 servers
    • server.listen([port[, host[, backlog]]][, callback]) for TCP servers

    This 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);
  }
});
    path: string,
    listeningListener?: () => void
    ): this;

    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 servers
    • server.listen([port[, host[, backlog]]][, callback]) for TCP servers

    This 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);
  }
});
    options: ListenOptions,
    listeningListener?: () => void
    ): this;

    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 servers
    • server.listen([port[, host[, backlog]]][, callback]) for TCP servers

    This 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);
  }
});
    handle: any,
    backlog?: number,
    listeningListener?: () => void
    ): this;

    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 servers
    • server.listen([port[, host[, backlog]]][, callback]) for TCP servers

    This 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);
  }
});
    handle: any,
    listeningListener?: () => void
    ): this;

    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 servers
    • server.listen([port[, host[, backlog]]][, callback]) for TCP servers

    This 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);
  }
});
  • eventName: E,
    listener?: (...args: ServerEventMap<Request, Response>[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 eventName

    The name of the event being listened for

    @param listener

    The event handler function

    eventName: string | symbol,
    listener?: (...args: any[]) => 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 eventName

    The name of the event being listened for

    @param listener

    The event handler function

  • listeners<E extends keyof ServerEventMap<typeof IncomingMessage, typeof ServerResponse>>(
    eventName: E
    ): (...args: ServerEventMap<Request, Response>[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] ]
    eventName: string | symbol
    ): (...args: any[]) => 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] ]
  • off<E extends keyof ServerEventMap<typeof IncomingMessage, typeof ServerResponse>>(
    eventName: E,
    listener: (...args: ServerEventMap<Request, Response>[E]) => void
    ): this;

    Alias for emitter.removeListener().

    eventName: string | symbol,
    listener: (...args: any[]) => void
    ): this;

    Alias for emitter.removeListener().

  • on<E extends keyof ServerEventMap<typeof IncomingMessage, typeof ServerResponse>>(
    eventName: E,
    listener: (...args: ServerEventMap<Request, Response>[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 eventName

    The name of the event.

    @param listener

    The callback function

    eventName: string | symbol,
    listener: (...args: any[]) => 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 eventName

    The name of the event.

    @param listener

    The callback function

  • once<E extends keyof ServerEventMap<typeof IncomingMessage, typeof ServerResponse>>(
    eventName: E,
    listener: (...args: ServerEventMap<Request, Response>[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 eventName

    The name of the event.

    @param listener

    The callback function

    eventName: string | symbol,
    listener: (...args: any[]) => 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 eventName

    The name of the event.

    @param listener

    The callback function

  • eventName: E,
    listener: (...args: ServerEventMap<Request, Response>[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 eventName

    The name of the event.

    @param listener

    The callback function

    eventName: string | symbol,
    listener: (...args: any[]) => 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 eventName

    The name of the event.

    @param listener

    The callback function

  • eventName: E,
    listener: (...args: ServerEventMap<Request, Response>[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 eventName

    The name of the event.

    @param listener

    The callback function

    eventName: string | symbol,
    listener: (...args: any[]) => 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 eventName

    The name of the event.

    @param listener

    The callback function

  • rawListeners<E extends keyof ServerEventMap<typeof IncomingMessage, typeof ServerResponse>>(
    eventName: E
    ): (...args: ServerEventMap<Request, Response>[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');
    eventName: string | symbol
    ): (...args: any[]) => 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');
  • ref(): this;

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

  • 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.

    eventName?: string | symbol
    ): 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.

  • eventName: E,
    listener: (...args: ServerEventMap<Request, Response>[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.

    eventName: string | symbol,
    listener: (...args: any[]) => 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.

  • 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.

  • msecs?: number,
    callback?: (socket: Socket) => void
    ): this;

    Sets the timeout value for sockets, and emits a 'timeout' event on the Server object, passing the socket as an argument, if a timeout occurs.

    If there is a 'timeout' event listener on the Server object, then it will be called with the timed-out socket as an argument.

    By default, the Server does not timeout sockets. However, if a callback is assigned to the Server's 'timeout' event, timeouts must be handled explicitly.

    callback: (socket: Socket) => void
    ): this;

    Sets the timeout value for sockets, and emits a 'timeout' event on the Server object, passing the socket as an argument, if a timeout occurs.

    If there is a 'timeout' event listener on the Server object, then it will be called with the timed-out socket as an argument.

    By default, the Server does not timeout sockets. However, if a callback is assigned to the Server's 'timeout' event, timeouts must be handled explicitly.

  • unref(): this;

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

interface ServerOptions<Request extends typeof IncomingMessage = typeof IncomingMessage, Response extends typeof ServerResponse = typeof ServerResponse>

  • connectionsCheckingInterval?: number

    Sets the interval value in milliseconds to check for request and headers timeout in incomplete requests.

  • headersTimeout?: number

    Sets the timeout value in milliseconds for receiving the complete HTTP headers from the client. See Server.headersTimeout for more information.

  • highWaterMark?: number

    Optionally overrides all sockets' readableHighWaterMark and writableHighWaterMark. This affects highWaterMark property of both IncomingMessage and ServerResponse. Default:

  • IncomingMessage?: Request

    Specifies the IncomingMessage class to be used. Useful for extending the original IncomingMessage.

  • insecureHTTPParser?: boolean

    Use an insecure HTTP parser that accepts invalid HTTP headers when true. Using the insecure parser should be avoided. See --insecure-http-parser for more information.

  • joinDuplicateHeaders?: boolean

    It joins the field line values of multiple headers in a request with , instead of discarding the duplicates.

  • keepAlive?: boolean

    If set to true, it enables keep-alive functionality on the socket immediately after a new incoming connection is received, similarly on what is done in socket.setKeepAlive([enable][, initialDelay]).

  • keepAliveInitialDelay?: number

    If set to a positive number, it sets the initial delay before the first keepalive probe is sent on an idle socket.

  • keepAliveTimeout?: number

    The number of milliseconds of inactivity a server needs to wait for additional incoming data, after it has finished writing the last response, before a socket will be destroyed.

  • keepAliveTimeoutBuffer?: number

    An additional buffer time added to the server.keepAliveTimeout to extend the internal socket timeout.

  • maxHeaderSize?: number

    Optionally overrides the value of --max-http-header-size for requests received by this server, i.e. the maximum length of request headers in bytes.

  • noDelay?: boolean

    If set to true, it disables the use of Nagle's algorithm immediately after a new incoming connection is received.

  • optimizeEmptyRequests?: boolean

    If set to true, requests without Content-Length or Transfer-Encoding headers (indicating no body) will be initialized with an already-ended body stream, so they will never emit any stream events (like 'data' or 'end'). You can use req.readableEnded to detect this case.

  • rejectNonStandardBodyWrites?: boolean

    If set to true, an error is thrown when writing to an HTTP response which does not have a body.

  • requestTimeout?: number

    Sets the timeout value in milliseconds for receiving the entire request from the client.

  • requireHostHeader?: boolean

    If set to true, it forces the server to respond with a 400 (Bad Request) status code to any HTTP/1.1 request message that lacks a Host header (as mandated by the specification).

  • ServerResponse?: Response

    Specifies the ServerResponse class to be used. Useful for extending the original ServerResponse.

  • shouldUpgradeCallback?: (request: InstanceType<Request>) => boolean

    A callback which receives an incoming request and returns a boolean, to control which upgrade attempts should be accepted. Accepted upgrades will fire an 'upgrade' event (or their sockets will be destroyed, if no listener is registered) while rejected upgrades will fire a 'request' event like any non-upgrade request.

  • uniqueHeaders?: string | string[][]

    A list of response headers that should be sent only once. If the header's value is an array, the items will be joined using ; .