simple go chatroom

tcp.go

package main

import (
	"flag"
	"fmt"
	"io"
	"net"
	"sync"
	"time"
)

func checkError(err error) {
	if err != nil {
		panic(err)
	}
}

func main() {

	isServer := flag.Bool("s", false, "running as server")
	flag.Parse()

	if *isServer {
		addr, err := net.ResolveTCPAddr("tcp", ":11000")
		checkError(err)

		listener, err := net.ListenTCP("tcp", addr)
		checkError(err)

		var connPool []*net.TCPConn
		mutex := &sync.Mutex{}

		go func() {
			for {
				if conn, err := listener.AcceptTCP(); err != nil {
					fmt.Printf("%v\n", err)
				} else {
					mutex.Lock()
					connPool = append(connPool, conn)
					mutex.Unlock()

					fmt.Printf("New connection %v %v\n", conn.LocalAddr(), conn.RemoteAddr())
					go func(conn *net.TCPConn) {
						conn.Write([]byte(fmt.Sprintf("Hi From Server\n")))

						buf := make([]byte, 128)
						for {
							if n, err := conn.Read(buf); err != nil {
								if err != io.EOF {
									fmt.Printf("%v\n", err)
								} else {
									mutex.Lock()
									for k, v := range connPool {
										if v == conn {
											connPool = append(connPool[:k], connPool[k+1:]...)
											break
										}
									}
									mutex.Unlock()
									fmt.Printf("Connection closed\n")
								}
								break
							} else {
								fmt.Printf("Received %d byte of data from %v:\n%v\n", n, conn, buf[:n])
								for _, v := range connPool {
									obuf := []byte(fmt.Sprintf("%v: ", conn.RemoteAddr()))
									obuf = append(obuf, buf[:n]...)
									v.Write(obuf)
								}
							}
						}
					}(conn)
				}
			}
		}()

		quit := make(chan bool)
		<-quit
	} else {

		serverAddr, err := net.ResolveTCPAddr("tcp", "127.0.0.1:11000")
		checkError(err)

		localAddr, err := net.ResolveTCPAddr("tcp", ":0")
		checkError(err)

		conn, err := net.DialTCP("tcp", localAddr, serverAddr)
		checkError(err)

		go func(conn *net.TCPConn) {
			buf := make([]byte, 128)
			for {
				if n, err := conn.Read(buf); err != nil {
					if err != io.EOF {
						fmt.Printf("%v\n", err)
					} else {
						fmt.Printf("Disconnected from Server\n")
					}
					break
				} else {
					fmt.Printf("Received %d byte of data from %v:\n%v\n", n, conn, buf[:n])
				}
			}
		}(conn)

		conn.Write([]byte(fmt.Sprintf("Hi!\n")))
		time.Sleep(3 * time.Second)
		conn.Write([]byte(fmt.Sprintf("I am a bot\n")))
		time.Sleep(2 * time.Second)
		conn.Write([]byte(fmt.Sprintf("Bye\n")))
		time.Sleep(1 * time.Second)
		conn.Close()
	}
}