tcp.go

package main

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

const Message string = "Hello World!\n"
const ServerPort string = "173.250.148.245"

func main() {
	if len(os.Args) < 2 {
		panic("not enough args")
	}
	if os.Args[1] == "server" {
		server()
	} else if os.Args[1] == "client" {
		client()
	} else {
		panic("bad args")
	}

}

func server() {
	ln, err := net.Listen("tcp", ":80")
	if err != nil {
		panic(err)
	}
	for {
		conn, err := ln.Accept()
		if err != nil {
			panic(err)
		}
		fmt.Printf("local addr: %v\n", conn.LocalAddr())
		fmt.Printf("remote addr: %v\n", conn.RemoteAddr())
		bs := make([]byte, len(Message))
		n, err := conn.Read(bs)
		if err != nil {
			panic(err)
		}
		if n != len(Message) {
			panic("not enough bytes read")
		}
		fmt.Printf("message received: %s\n", string(bs))
		err = conn.Close()
		if err != nil {
			panic(err)
		}
	}
}

func client() {
	conn, err := net.Dial("tcp", ServerPort+":80")
	if err != nil {
		panic(err)
	}
	n, err := conn.Write([]byte(Message))
	if err != nil {
		panic(err)
	}
	if n != len(Message) {
		panic("not enough bytes written")
	}
	err = conn.Close()
	if err != nil {
		panic(err)
	}
	fmt.Println("success")
}