udp-ping-server.go

package main

// Run with ./server $PORT

import (
	"fmt"
	"net"
	"os"
)

func main() {
	// Check for the correct number of arguments
	if len(os.Args) != 2 {
		fmt.Fprintf(os.Stderr, "Usage: %s <port>\n", os.Args[0])
		os.Exit(1)
	}

	// The port on which the server will listen for UDP packets
	port := os.Args[1]

	// Resolve the UDP address
	addr, err := net.ResolveUDPAddr("udp", ":"+port)
	if err != nil {
		fmt.Println("Error resolving UDP address:", err)
		os.Exit(1)
	}

	// Create a UDP socket and listen on the specified port
	conn, err := net.ListenUDP("udp", addr)
	if err != nil {
		fmt.Println("Error listening on UDP port:", err)
		os.Exit(1)
	}
	defer conn.Close()

	fmt.Printf("UDP echo server listening on port %s\n", port)

	// Buffer to store received data
	buffer := make([]byte, 1024)

	for {
		// Read data from connection
		n, clientAddr, err := conn.ReadFromUDP(buffer)
		if err != nil {
			fmt.Println("Error reading from UDP:", err)
			continue
		}

		fmt.Printf("Received: %s from %s\n", string(buffer[:n]), clientAddr.String())

		// Echo data back to sender
		_, err = conn.WriteToUDP(buffer[:n], clientAddr)
		if err != nil {
			fmt.Println("Error writing to UDP:", err)
			continue
		}
	}
}