net.createServer

History

net.createServer(options?, connectionListener?): net.Server

Attributes

options:Object

allowHalfOpen?:boolean

If set to false, then the socket will automatically end the writable side when the readable side ends. Default: false.

highWaterMark?:number

Optionally overrides all net.Sockets' readableHighWaterMark and writableHighWaterMark. Default: See stream.getDefaultHighWaterMark().

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(). Default: false.

keepAliveInitialDelay?:number

If set to a positive number, it sets the initial delay before the first keepalive probe is sent on an idle socket. Default: 0.

noDelay?:boolean

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

pauseOnConnect?:boolean

Indicates whether the socket should be paused on incoming connections. Default: false.

blockList:net.BlockList

blockList can be used for disabling inbound access to specific IP addresses, IP ranges, or IP subnets. This does not work if the server is behind a reverse proxy, NAT, etc. because the address checked against the block list is the address of the proxy, or the one specified by the NAT.

connectionListener:Function

Automatically set as a listener for the 'connection' event.

Returns:net.Server

Creates a new TCP or IPC server.

If allowHalfOpen is set to true, when the other end of the socket signals the end of transmission, the server will only send back the end of transmission when socket.end() is explicitly called. For example, in the context of TCP, when a FIN packet is received, a FIN packet is sent back only when socket.end() is explicitly called. Until then the connection is half-closed (non-readable but still writable). See 'end' event and RFC 1122 (section 4.2.2.13) for more information.

If pauseOnConnect is set to true, then the socket associated with each incoming connection will be paused, and no data will be read from its handle. This allows connections to be passed between processes without any data being read by the original process. To begin reading data from a paused socket, call socket.resume().

The server can be a TCP server or an IPC server, depending on what it listen() to.

Here is an example of a TCP echo server which listens for connections on port 8124:

import net from 'node:net';
const server = net.createServer((c) => {
  // 'connection' listener.
  console.log('client connected');
  c.on('end', () => {
    console.log('client disconnected');
  });
  c.write('hello\r\n');
  c.pipe(c);
});
server.on('error', (err) => {
  throw err;
});
server.listen(8124, () => {
  console.log('server bound');
});

JavaScript

const net = require('node:net');
const server = net.createServer((c) => {
  // 'connection' listener.
  console.log('client connected');
  c.on('end', () => {
    console.log('client disconnected');
  });
  c.write('hello\r\n');
  c.pipe(c);
});
server.on('error', (err) => {
  throw err;
});
server.listen(8124, () => {
  console.log('server bound');
});

JavaScript

Test this by using telnet:

telnet localhost 8124

To listen on the socket /tmp/echo.sock:

server.listen('/tmp/echo.sock', () => {
  console.log('server bound');
});

JavaScript

Use nc to connect to a Unix domain socket server:

nc -U /tmp/echo.sock