udp-echoserv.go

package main

// usage:
// Start udp-echoserv.go and use the commandline tool sendip
// $ sendip -p ipv4 -is 192.168.1.81 -p udp -us 5070 -ud 5000  -d "Hello, World" -v 127.0.0.1
// where -is and -us are arbitrary and -ud is the port used in ResolveUDPAddr

import (
	"fmt"
	"net"
)

func main() {
	comm := make(chan string)
	go func(c chan string) {
		addr, err := net.ResolveUDPAddr("udp", ":5000")
		if err != nil {
			fmt.Println("Error", err)
		}

		l, err := net.ListenUDP("udp", addr)
		if err != nil {
			fmt.Println("Error", err)
		}
		data := make([]byte, 255)

		for {
			length, packet_addr, err := l.ReadFromUDP(data)
			if err != nil {
				fmt.Println("Error", err)
			}
			c <- fmt.Sprintf("UDP Echo: %s (%d) from %s", data, length, packet_addr)
		}
	}(comm)

	for {
		select {
		case info := <-comm:
			fmt.Println(info)
		}
	}
}