echoserver - A simple TCP echo server written in Go

echoserver.go

// echoserver - A simple TCP echo server written in Go
//
// Build:
// % go build echoserver.go
//
// Usage:
// % ./echoserver 8080
//
// License:
// BSD 3-clause Revised
// Copyright (c) 2016, Bayu Aldi Yansyah <[email protected]>
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//     1. Redistributions of source code must retain the above copyright
//        notice, this list of conditions and the following disclaimer.
//     2. Redistributions in binary form must reproduce the above copyright
//        notice, this list of conditions and the following disclaimer in the
//        documentation and/or other materials provided with the distribution.
//     3. Neither the name of the copyright holder nor the names of its
//        contributors may be used to endorse or promote products derived
//        from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
// OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
// OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
// ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
package main

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

func echo(conn net.Conn) {
	_, err := io.Copy(conn, conn)
	if err != nil {
		log.Println(err)
		return
	}
	err = conn.Close()
	if err != nil {
		log.Println(err)
		return
	}
}

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

	listener, err := net.Listen("tcp", ":"+os.Args[1])
	if err != nil {
		log.Fatal(err)
	}
	defer listener.Close()

	log.Printf("echoserver: listening on port :%s", os.Args[1])
	for {
		conn, err := listener.Accept()
		if err != nil {
			log.Println(err)
			continue
		}
		go echo(conn)
	}
}