UDP Server

import dgram from 'node:dgram'
 
const server = dgram.createSocket('udp4')
 
server.on('error', err => {
  console.error(err)
  server.close()
})
 
server.on('message', (msg, rinfo) => {
  const data = msg.toString('utf8').trim()
  console.log(`received: ${data} from ${rinfo.address}:${rinfo.port}`)
})
 
server.on('listening', () => {
  const address = server.address()
  console.log(`server listening ${address.address}:${address.port}`)
})
 
server.bind(3000)

package main
 
import (
	"fmt"
	"net"
	"strings"
)
 
func main() {
	conn, err := net.ListenUDP("udp", &net.UDPAddr{
		Port: 3000,
		IP:   net.ParseIP("0.0.0.0"),
	})
	if err != nil {
		panic(err)
	}
 
	defer conn.Close()
	fmt.Printf("server listening %s\n", conn.LocalAddr().String())
 
	for {
		message := make([]byte, 20)
		rlen, remote, err := conn.ReadFromUDP(message[:])
		if err != nil {
			panic(err)
		}
 
		data := strings.TrimSpace(string(message[:rlen]))
		fmt.Printf("received: %s from %s\n", data, remote)
	}
}

use std::net::UdpSocket;
 
fn main() {
    let socket = UdpSocket::bind("0.0.0.0:3000").unwrap();
    println!("server listening {}", socket.local_addr().unwrap());
 
    let mut buf = [0u8; 20];
    loop {
        let (len, remote) = socket.recv_from(&mut buf).unwrap();
        let data = String::from_utf8_lossy(&buf[..len]);
        let data = data.trim();
        println!("received: {data} from {remote}");
    }
}

import Network
 
let listener = try NWListener(using: .udp, on: 3000)
print("server listening 0.0.0.0:3000")
 
listener.newConnectionHandler = { connection in
    connection.start(queue: .main)
    connection.receiveMessage { data, _, _, _ in
        if let data, let text = String(data: data, encoding: .utf8) {
            let endpoint = connection.currentPath?.remoteEndpoint
            print("received: \(text.trimmingCharacters(in: .whitespacesAndNewlines)) from \(endpoint?.debugDescription ?? "?")")
        }
        connection.cancel() // mỗi datagram từ một địa chỉ mới sinh ra một "connection" giả riêng
    }
}
 
listener.start(queue: .main)
dispatchMain()

void main() throws Exception {
    try (var socket = new DatagramSocket(3000)) {
        IO.println("server listening 0.0.0.0:3000");
 
        byte[] buf = new byte[20];
        while (true) {
            var packet = new DatagramPacket(buf, buf.length);
            socket.receive(packet);
 
            String data = new String(packet.getData(), 0, packet.getLength()).trim();
            IO.println("received: " + data + " from " + packet.getAddress().getHostAddress() + ":" + packet.getPort());
        }
    }
}