How to create UDP server with Node.js.

Overview

This article is going to talk about how to use UDP server in Node.js. The codes in this article are written by Typescript. There will be two examples such as Server and Client.

Setup project

Setup Typescript project. You can pass this step

shell

npm init -y

start Node.js package

shell

npm i ts-node

ts-node is used for running typescript file without compiling

Setup server

typescript

import { createSocket } from 'dgram'

const server = createSocket('udp4')
server.bind(12778)

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

server.on('message', (msg, remote) => {
  console.log(`Serve get message: ${msg.toString()} from ${remote.address}:${remote.port}`)
})
server.on('close', () => {
  console.log('Close successfully')
})

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

Server will run on port 12778 with 0:0:0:0 address

createSocket(type or options , callback)

typescript

import { createSocket } from 'dgram'

const server = createSocket('udp4')

createSocket function returns socket object.

Parameter

types string: udp4 or udp6
or
options

type string: The family of socket. Must be either 'udp4' or 'udp6'. Required.
reuseAddr boolean: When true socket.bind() will reuse the address, even if another process has already bound a socket on it. Default: false.
ipv6Only boolean: Setting ipv6Only to true will disable dual-stack support, i.e., binding to address :: won't make 0.0.0.0 be bound. Default: false.
recvBufferSize number: Sets the SO_RCVBUF socket value.
sendBufferSize number: Sets the SO_SNDBUF socket value.
lookup Function: Custom lookup function. Default: dns.lookup().
signal AbortSignal: An AbortSignal that may be used to close a socket.

and
callback Function : Attached as listener to message events

bind([port][, address], callback) function

typescript

server.bind(12778) // set port
server.bind('127.0.0.1') // set address

bind function is used for binding port and address.
You don't have to bind an address. If address is not passed, default address is 0:0:0:0.

on()

typescript

server.on('listening', () => {...})
server.on('message', (msg, remote) => {...})
server.on('close', () => {...})
server.on('error', (err) => {...})

Listen events that is passed in parameter. Following table is the events list that socket listen

Events	Description
close	It's emitted after a socket is closed with `close()` functions
connect	It's emitted after a socket is connected with remote address successfully
error	It's emitted after a socket encounters errors
listening	It's emitted once after `bind` functions
message	It's emitted whenever a new message buffer is available on socket

close(callback)

typescript

server.close()

Close socket and stop listening for buffer data

Setup client

The way to setup client is very similar as server

typescript

import { createSocket } from 'dgram'

const client = createSocket('udp4')
client.bind(12777)

let clientCount = 0
const interval = setInterval(() => {
  const messageBuffer = Buffer.from(`Client send a data to server. Time: ${new Date().toISOString()}`)
  client.send(messageBuffer, 0, messageBuffer.length, 12778, (error, bytes) => {
    if (error) {
      console.error(error)
      throw error
    }
    if (clientCount++ >= 10) {
      client.close()
      clearInterval(interval)
    }
  })
}, 1000)

Client will run on port 12777 with 0:0:0:0 address
Client will send a message buffer to the server which port is 12778 every a second

send(msg[, offset, length][, port][, address], callback)

typescript

const messageBuffer = Buffer.from(`Client send a data to server. Time: ${new Date().toISOString()}`)
client.send(messageBuffer, 0, messageBuffer.length, 12778, (error, bytes) => {
  if (error) {
    console.error(error)
    throw error
  }
  if (clientCount++ >= 10) {
    client.close()
    clearInterval(interval)
  }
})

Send message buffer to port and address which are passed as parameters.
Address can be ignored and default address will be 0:0:0:0

Send multiple messages

typescript

const data1 = Buffer.from('hello')
const data2 = Buffer.from('world')

client.send([data1, data2], 12778, (error) => {
  if (error) {
    console.error(error)
    throw error
  }
})

send() function allows to send more than one message buffer to the server. server will receive data as a combined message likehelloworld