package main
import (
"net"
"fmt"
)
var (   maxRead = 1100
    msgStop   = []byte("cmdStop")
    msgStart  = []byte("cmdContinue")
    )
func main() {
 
    hostAndPort := "localhost:54321"
    listener := initServer(hostAndPort)
    for {
        conn, err := listener.Accept()
        checkError(err, "Accept: ")
        go connectionHandler(conn)
    }
}
func initServer(hostAndPort string) *net.TCPListener {
    serverAddr, err := net.ResolveTCPAddr("tcp", hostAndPort)
    checkError(err, "Resolving address:port failed: '" + hostAndPort + "'")
    listener, err := net.ListenTCP("tcp", serverAddr)
    checkError(err, "ListenTCP: ")
    println("Listening to: ", listener.Addr().String())
    return listener
}
func connectionHandler(conn net.Conn) {
    connFrom := conn.RemoteAddr().String()
    println("Connection from: ", connFrom)
    talktoclients(conn)
    for {
        var ibuf []byte = make([]byte, maxRead + 1)
        length, err := conn.Read(ibuf[0:maxRead])
        ibuf[maxRead] = 0 // to prevent overflow
    switch err {
    case nil:
        handleMsg(length, err, ibuf)
    default:
        goto DISCONNECT
    }
    }
    DISCONNECT:
    err := conn.Close()
    println("Closed connection:" , connFrom)
    checkError(err, "Close:" )
    }
func talktoclients(to net.Conn) {
    wrote, err := to.Write(msgStart)
    checkError(err, "Write: wrote " + string(wrote) + " bytes.")
}
func handleMsg(length int, err error, msg []byte) {
    if length > 0 {
         
        for i := 0; ; i++ {
            if msg[i] == 0 {
                break
            }
        }
        fmt.Printf("Received data: %v", string(msg[0:length]))
        fmt.Println("   length:",length)
    }
}
func checkError(error error, info string) {
    if error != nil {
panic("ERROR: " + info + " " + error.Error()) // terminate program
}
}