rasd.go

/**
 * RASServer
 *
 * cf. https://ipfs.io/ipfs/QmfYeDhGH9bZzihBUDEQbCbTc5k5FZKURMUoUvfmc27BwL/socket/udp_datagrams.html
 */

package main

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

func main() {

	if len(os.Args) != 2 {
		fmt.Fprintf(os.Stderr, "Usage: %s ipaddress:port\n", os.Args[0])
		os.Exit(1)
	}

	addr, err := net.ResolveUDPAddr("udp", os.Args[1])
	check(err)

	conn, err := net.ListenUDP("udp", addr)
	check(err)
	defer conn.Close()

	buf := make([]byte, 1024)

	for {
		size, addr, err := conn.ReadFromUDP(buf)
		if err == nil {
			fmt.Printf("%s\t%s\n", addr, string(buf[0:size]))
		} else {
			fmt.Printf("Error: %s\n", err)
		}
	}
}

func check(err error) {
	if err != nil {
		fmt.Println("Error: ", err)
		os.Exit(0)
	}
}

send2ras.go

/**
 * send2ras - send a command to an RAS server
 */

package main

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

func main() {

	if len(os.Args) != 3 {
		fmt.Fprintf(os.Stderr, "Usage: %s host:port message\n", os.Args[0])
		os.Exit(1)
	}

	ServerAddr, err := net.ResolveUDPAddr("udp", os.Args[1])
	checkError(err)

	LocalAddr, err := net.ResolveUDPAddr("udp", "127.0.0.1:0")
	checkError(err)

	Conn, err := net.DialUDP("udp", LocalAddr, ServerAddr)
	checkError(err)

	_, err = Conn.Write([]byte(os.Args[2]))
	checkError(err)
}

func checkError(err error) {
	if err != nil {
		fmt.Println("Error: ", err)
	}
}

go build -ldflags "-s"

https://astaxie.gitbooks.io/build-web-application-with-golang/en/

https://scotch.io/bar-talk/build-a-realtime-chat-server-with-go-and-websockets