nc golang

nc.go

package main

import (
	"fmt"
	"io"
	"net"
	"os"
	"sync"
)

const tcp = "tcp"

/**

(this is the right answer)

linux nc command port to golang


in nc , we can do this



echo 'my id is 1' > /tmp/1
echo 'my id is 3' > /tmp/3
rm -rf /tmp/2 /tmp/4


server

nc -l 19090 < /tmp/1 > /tmp/2
( if you are in linux not mac this may be  ` nc -l -p 19090 `  )

client

nc 127.0.0.1 19090 < /tmp/3 > /tmp/4

when finish ,both server and client will be closed

client send /tmp/3 is saved by server to /tmp/2

server send /tmp/1 is saved by server to /tmp/4

then use golang do the same thing , but when finished , both server and client can not closed automaticly


echo 'my id is 1' > /tmp/1
echo 'my id is 3' > /tmp/3
rm -rf /tmp/2 /tmp/4

./nc serer < /tmp/1 > /tmp/2


./nc  < /tmp/3 > /tmp/4


**/

func main() {
	if len(os.Args) > 1 {
		fmt.Fprintf(os.Stderr, "run as server\n")
		server()
	} else {
		fmt.Fprintf(os.Stderr, "run as client\n")
		client()
	}
}

func server() error {
	port := "19088"
	l, err := net.Listen(tcp, ":"+port)
	if err != nil {
		return err
	}
	defer l.Close()
	conn, err := l.Accept()
	if err != nil {
		return err
	}
	var wg sync.WaitGroup
	wg.Add(2)
	tcpconn := conn.(*net.TCPConn)
	go func() {
		io.Copy(tcpconn, os.Stdin)
		fmt.Fprintln(os.Stderr, "os.Stdin 2 conn done")
		tcpconn.CloseWrite()
		wg.Done()
	}()
	go func() {
		io.Copy(os.Stdout, tcpconn)
		fmt.Fprintln(os.Stderr, "conn 2 os.Stdout done")
		tcpconn.CloseRead()
		wg.Done()
	}()
	wg.Wait()
	return nil
}

func client() error {
	addr := "127.0.0.1:19088"
	conn, err := net.Dial(tcp, addr)
	if err != nil {
		return err
	}
	tcpconn := conn.(*net.TCPConn)
	var wg sync.WaitGroup
	wg.Add(2)
	go func() {
		io.Copy(tcpconn, os.Stdin)
		fmt.Fprintln(os.Stderr, "conn 2 os.Stdin done")
		tcpconn.CloseWrite()
		wg.Done()
	}()
	go func() {
		io.Copy(os.Stdout, tcpconn)
		fmt.Fprintln(os.Stderr, "os.Stdout 2 conn done")
		tcpconn.CloseRead()
		wg.Done()
	}()
	wg.Wait()
	return nil
}

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