/* Copyright (C) 2014 by Alexandru Cojocaru */

/* This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>. */

package main

import (
	"log"
	"net"
)

var sem = make(chan int, 100)

func echo(con net.PacketConn) {
	defer func() { <-sem }()
	buf := make([]byte, 4096)
	nr, addr, err := con.ReadFrom(buf)
	if err != nil {
		log.Print(err)
		return
	}
	nw, err := con.WriteTo(buf[:nr], addr)
	if err != nil {
		log.Print(err)
		return
	}
	if nw != nr {
		log.Printf("received %d bytes but sent %d\n", nr, nw)
	}
}

func main() {
	log.SetFlags(log.Lshortfile)
	con, err := net.ListenPacket("udp", ":7")
	if err != nil {
		log.Fatal(err)
	}
	for {
		sem <- 1
		go echo(con)
	}
	err = con.Close()
	if err != nil {
		log.Fatal(err)
	}
}