@fkn/lib/dgram

Classes

Socket

Extends

• EventEmitter

Implements

• Socket

Constructors

Constructor

new Socket(options): Socket;

Parameters

options

SocketOptions & EventEmitterOptions & object

Returns

Socket

Overrides

EventEmitter.constructor

Methods

[asyncDispose]()

asyncDispose: Promise<void>;

Returns

Promise<void>

Implementation of

DgramSocket.[asyncDispose]

addMembership()

addMembership(multicastAddress, multicastInterface?): void;

Tells the kernel to join a multicast group at the given multicastAddress and multicastInterface using the IP_ADD_MEMBERSHIP socket option. If the multicastInterface argument is not specified, the operating system will choose one interface and will add membership to it. To add membership to every available interface, call addMembership multiple times, once per interface.

When called on an unbound socket, this method will implicitly bind to a random port, listening on all interfaces.

When sharing a UDP socket across multiple cluster workers, thesocket.addMembership() function must be called only once or anEADDRINUSE error will occur:

import cluster from 'node:cluster';
import dgram from 'node:dgram';

if (cluster.isPrimary) {
  cluster.fork(); // Works ok.
  cluster.fork(); // Fails with EADDRINUSE.
} else {
  const s = dgram.createSocket('udp4');
  s.bind(1234, () => {
    s.addMembership('224.0.0.114');
  });
}

Parameters

multicastAddress

string

multicastInterface?

string

Returns

void

Since

v0.6.9

Implementation of

DgramSocket.addMembership

address()

address(): AddressInfo;

Returns an object containing the address information for a socket. For UDP sockets, this object will contain address, family, and port properties.

This method throws EBADF if called on an unbound socket.

Returns

AddressInfo

Since

v0.1.99

Implementation of

DgramSocket.address

addSourceSpecificMembership()

addSourceSpecificMembership(
   sourceAddress,
   groupAddress,
   multicastInterface?): void;

Not implemented by the browser transport. This method currently does nothing.

Parameters

sourceAddress

string

groupAddress

string

multicastInterface?

string

Returns

void

Implementation of

DgramSocket.addSourceSpecificMembership

bind()

Call Signature

bind(
   port?,
   address?,
   callback?): this;

For UDP sockets, causes the dgram.Socket to listen for datagram messages on a named port and optional address. If port is not specified or is 0, the operating system will attempt to bind to a random port. If address is not specified, the operating system will attempt to listen on all addresses. Once binding is complete, a 'listening' event is emitted and the optional callback function is called.

Specifying both a 'listening' event listener and passing a callback to the socket.bind() method is not harmful but not very useful.

A bound datagram socket keeps the Node.js process running to receive datagram messages.

If binding fails, an 'error' event is generated. In rare case (e.g. attempting to bind with a closed socket), an Error may be thrown.

Example of a UDP server listening on port 41234:

import dgram from 'node:dgram';

const server = dgram.createSocket('udp4');

server.on('error', (err) => {
  console.error(`server error:\n${err.stack}`);
  server.close();
});

server.on('message', (msg, rinfo) => {
  console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);
});

server.on('listening', () => {
  const address = server.address();
  console.log(`server listening ${address.address}:${address.port}`);
});

server.bind(41234);
// Prints: server listening 0.0.0.0:41234

Parameters

port?

number

address?

string

callback?

() => void

with no parameters. Called when binding is complete.

Returns

this

Since

v0.1.99

Implementation of

DgramSocket.bind

Call Signature

bind(port?, callback?): this;

Parameters

port?

number

callback?

() => void

Returns

this

Implementation of

DgramSocket.bind

Call Signature

bind(callback?): this;

Parameters

callback?

() => void

Returns

this

Implementation of

DgramSocket.bind

Call Signature

bind(options, callback?): this;

Parameters

options

BindOptions

callback?

() => void

Returns

this

Implementation of

DgramSocket.bind

close()

close(callback?): this;

Close the underlying socket and stop listening for data on it. If a callback is provided, it is added as a listener for the 'close' event.

Parameters

callback?

() => void

Called when the socket has been closed.

Returns

this

Since

v0.1.99

Implementation of

DgramSocket.close

connect()

Call Signature

connect(
   port,
   address?,
   callback?): void;

Associates the dgram.Socket to a remote address and port. Every message sent by this handle is automatically sent to that destination. Also, the socket will only receive messages from that remote peer. Trying to call connect() on an already connected socket will result in an ERR_SOCKET_DGRAM_IS_CONNECTED exception. If address is not provided, '127.0.0.1' (for udp4 sockets) or '::1' (for udp6 sockets) will be used by default. Once the connection is complete, a 'connect' event is emitted and the optional callback function is called. In case of failure, the callback is called or, failing this, an 'error' event is emitted.

Parameters

port

number

address?

string

callback?

() => void

Called when the connection is completed or on error.

Returns

void

Since

v12.0.0

Implementation of

DgramSocket.connect

Call Signature

connect(port, callback): void;

Parameters

port

number

callback

() => void

Returns

void

Implementation of

DgramSocket.connect

disconnect()

disconnect(): void;

A synchronous function that disassociates a connected dgram.Socket from its remote address. Trying to call disconnect() on an unbound or already disconnected socket will result in an ERR_SOCKET_DGRAM_NOT_CONNECTED exception.

Returns

void

Since

v12.0.0

Implementation of

DgramSocket.disconnect

dropMembership()

dropMembership(multicastAddress, multicastInterface?): void;

Instructs the kernel to leave a multicast group at multicastAddress using the IP_DROP_MEMBERSHIP socket option. This method is automatically called by the kernel when the socket is closed or the process terminates, so most apps will never have reason to call this.

If multicastInterface is not specified, the operating system will attempt to drop membership on all valid interfaces.

Parameters

multicastAddress

string

multicastInterface?

string

Returns

void

Since

v0.6.9

Implementation of

DgramSocket.dropMembership

dropSourceSpecificMembership()

dropSourceSpecificMembership(
   sourceAddress,
   groupAddress,
   multicastInterface?): void;

Not implemented by the browser transport. This method currently does nothing.

Parameters

sourceAddress

string

groupAddress

string

multicastInterface?

string

Returns

void

Implementation of

DgramSocket.dropSourceSpecificMembership

getRecvBufferSize()

getRecvBufferSize(): number;

This method throws ERR_SOCKET_BUFFER_SIZE if called on an unbound socket.

Returns

number

the SO_RCVBUF socket receive buffer size in bytes.

Since

v8.7.0

Implementation of

DgramSocket.getRecvBufferSize

getSendBufferSize()

getSendBufferSize(): number;

This method throws ERR_SOCKET_BUFFER_SIZE if called on an unbound socket.

Returns

number

the SO_SNDBUF socket send buffer size in bytes.

Since

v8.7.0

Implementation of

DgramSocket.getSendBufferSize

getSendQueueCount()

getSendQueueCount(): number;

Queue measurements are not exposed by the browser transport. Always returns 0.

Returns

number

Implementation of

DgramSocket.getSendQueueCount

getSendQueueSize()

getSendQueueSize(): number;

Queue measurements are not exposed by the browser transport. Always returns 0.

Returns

number

Implementation of

DgramSocket.getSendQueueSize

ref()

ref(): this;

No-op in a browser, which has no Node process-liveness handle.

Returns

this

Implementation of

DgramSocket.ref

remoteAddress()

remoteAddress(): AddressInfo;

Returns an object containing the address, family, and port of the remote endpoint. This method throws an ERR_SOCKET_DGRAM_NOT_CONNECTED exception if the socket is not connected.

Returns

AddressInfo

Since

v12.0.0

Implementation of

DgramSocket.remoteAddress

send()

Call Signature

send(
   msg,
   port?,
   address?,
   callback?): void;

Broadcasts a datagram on the socket. For connectionless sockets, the destination port and address must be specified. Connected sockets, on the other hand, will use their associated remote endpoint, so the port and address arguments must not be set.

The msg argument contains the message to be sent. Depending on its type, different behavior can apply. If msg is a Buffer, any TypedArray or a DataView, the offset and length specify the offset within the Buffer where the message begins and the number of bytes in the message, respectively. If msg is a String, then it is automatically converted to a Buffer with 'utf8' encoding. With messages that contain multi-byte characters, offset and length will be calculated with respect to byte length and not the character position. If msg is an array, offset and length must not be specified.

The address argument is a string. If the value of address is a host name, DNS will be used to resolve the address of the host. If address is not provided or otherwise nullish, '127.0.0.1' (for udp4 sockets) or '::1' (for udp6 sockets) will be used by default.

If the socket has not been previously bound with a call to bind, the socket is assigned a random port number and is bound to the “all interfaces” address ('0.0.0.0' for udp4 sockets, '::0' for udp6 sockets.)

An optional callback function may be specified to as a way of reporting DNS errors or for determining when it is safe to reuse the buf object. DNS lookups delay the time to send for at least one tick of the Node.js event loop.

The only way to know for sure that the datagram has been sent is by using a callback. If an error occurs and a callback is given, the error will be passed as the first argument to the callback. If a callback is not given, the error is emitted as an 'error' event on the socket object.

Offset and length are optional but both must be set if either are used. They are supported only when the first argument is a Buffer, a TypedArray, or a DataView.

This method throws ERR_SOCKET_BAD_PORT if called on an unbound socket.

Example of sending a UDP packet to a port on localhost;

import dgram from 'node:dgram';
import { Buffer } from 'node:buffer';

const message = Buffer.from('Some bytes');
const client = dgram.createSocket('udp4');
client.send(message, 41234, 'localhost', (err) => {
  client.close();
});

Example of sending a UDP packet composed of multiple buffers to a port on127.0.0.1;

import dgram from 'node:dgram';
import { Buffer } from 'node:buffer';

const buf1 = Buffer.from('Some ');
const buf2 = Buffer.from('bytes');
const client = dgram.createSocket('udp4');
client.send([buf1, buf2], 41234, (err) => {
  client.close();
});

Sending multiple buffers might be faster or slower depending on the application and operating system. Run benchmarks to determine the optimal strategy on a case-by-case basis. Generally speaking, however, sending multiple buffers is faster.

Example of sending a UDP packet using a socket connected to a port on localhost:

import dgram from 'node:dgram';
import { Buffer } from 'node:buffer';

const message = Buffer.from('Some bytes');
const client = dgram.createSocket('udp4');
client.connect(41234, 'localhost', (err) => {
  client.send(message, (err) => {
    client.close();
  });
});

Parameters

msg

string | readonly any[] | Uint8Array<ArrayBufferLike>

Message to be sent.

port?

number

Destination port.

address?

string

Destination host name or IP address.

callback?

(error, bytes) => void

Called when the message has been sent.

Returns

void

Since

v0.1.99

Implementation of

DgramSocket.send

Call Signature

send(
   msg,
   port?,
   callback?): void;

Parameters

msg

string | readonly any[] | Uint8Array<ArrayBufferLike>

port?

number

callback?

(error, bytes) => void

Returns

void

Implementation of

DgramSocket.send

Call Signature

send(msg, callback?): void;

Parameters

msg

string | readonly any[] | Uint8Array<ArrayBufferLike>

callback?

(error, bytes) => void

Returns

void

Implementation of

DgramSocket.send

Call Signature

send(
   msg,
   offset,
   length,
   port?,
   address?,
   callback?): void;

Parameters

msg

string | Uint8Array<ArrayBufferLike>

offset

number

length

number

port?

number

address?

string

callback?

(error, bytes) => void

Returns

void

Implementation of

DgramSocket.send

Call Signature

send(
   msg,
   offset,
   length,
   port?,
   callback?): void;

Parameters

msg

string | Uint8Array<ArrayBufferLike>

offset

number

length

number

port?

number

callback?

(error, bytes) => void

Returns

void

Implementation of

DgramSocket.send

Call Signature

send(
   msg,
   offset,
   length,
   callback?): void;

Parameters

msg

string | Uint8Array<ArrayBufferLike>

offset

number

length

number

callback?

(error, bytes) => void

Returns

void

Implementation of

DgramSocket.send

Call Signature

send(
   msg,
   offset?,
   length?,
   port?,
   address?,
   callback?): void;

Parameters

msg

unknown

offset?

unknown

length?

unknown

port?

unknown

address?

unknown

callback?

unknown

Returns

void

Implementation of

DgramSocket.send

setBroadcast()

setBroadcast(flag): void;

Sets or clears the SO_BROADCAST socket option. When set to true, UDP packets may be sent to a local interface’s broadcast address.

This method throws EBADF if called on an unbound socket.

Parameters

flag

boolean

Returns

void

Since

v0.6.9

Implementation of

DgramSocket.setBroadcast

setMulticastInterface()

setMulticastInterface(multicastInterface): void;

No-op. The browser transport does not expose an interface index or address.

Parameters

multicastInterface

string

Returns

void

Implementation of

DgramSocket.setMulticastInterface

setMulticastLoopback()

setMulticastLoopback(flag): boolean;

Sets or clears the IP_MULTICAST_LOOP socket option. When set to true, multicast packets will also be received on the local interface.

This method throws EBADF if called on an unbound socket.

Parameters

flag

boolean

Returns

boolean

Since

v0.3.8

Implementation of

DgramSocket.setMulticastLoopback

setMulticastTTL()

setMulticastTTL(ttl): number;

Sets the IP_MULTICAST_TTL socket option. While TTL generally stands for “Time to Live”, in this context it specifies the number of IP hops that a packet is allowed to travel through, specifically for multicast traffic. Each router or gateway that forwards a packet decrements the TTL. If the TTL is decremented to 0 by a router, it will not be forwarded.

The ttl argument may be between 0 and 255. The default on most systems is 1.

This method throws EBADF if called on an unbound socket.

Parameters

ttl

number

Returns

number

Since

v0.3.8

Implementation of

DgramSocket.setMulticastTTL

setRecvBufferSize()

setRecvBufferSize(size): void;

Sets the SO_RCVBUF socket option. Sets the maximum socket receive buffer in bytes.

This method throws ERR_SOCKET_BUFFER_SIZE if called on an unbound socket.

Parameters

size

number

Returns

void

Since

v8.7.0

Implementation of

DgramSocket.setRecvBufferSize

setSendBufferSize()

setSendBufferSize(size): void;

Sets the SO_SNDBUF socket option. Sets the maximum socket send buffer in bytes.

This method throws ERR_SOCKET_BUFFER_SIZE if called on an unbound socket.

Parameters

size

number

Returns

void

Since

v8.7.0

Implementation of

DgramSocket.setSendBufferSize

setTTL()

setTTL(ttl): number;

Sets the IP_TTL socket option. While TTL generally stands for “Time to Live”, in this context it specifies the number of IP hops that a packet is allowed to travel through. Each router or gateway that forwards a packet decrements the TTL. If the TTL is decremented to 0 by a router, it will not be forwarded. Changing TTL values is typically done for network probes or when multicasting.

The ttl argument may be between 1 and 255. The default on most systems is 64.

This method throws EBADF if called on an unbound socket.

Parameters

ttl

number

Returns

number

Since

v0.1.101

Implementation of

DgramSocket.setTTL

unref()

unref(): this;

No-op in a browser, which has no Node process-liveness handle.

Returns

this

Implementation of

DgramSocket.unref

Variables

default

default: object;

Type Declaration

createSocket

createSocket: (options, callback?) => Socket;

Parameters

options

SocketOptions | SocketType

callback?

(msg, rinfo) => void

Returns

Socket

Socket

Socket: typeof Socket;

Functions

createSocket()

function createSocket(options, callback?): Socket;

Parameters

options

SocketOptions | SocketType

callback?

(msg, rinfo) => void

Returns

Socket