如何在net.Con中正确地对消息进行分块并防止广播

Question

Updated with solution: http://play.golang.org/p/Skgk9reT6c

http://play.golang.org/p/gtWYPXRsKo

without goroutines: http://play.golang.org/p/Vgne7e3RVO

Question 1: Why is it that the message "YOU'LL NEVER SEE ME!" doesn't display?

Question 2: As soon as I initiate a client I send these messages, all on their own threads:

func client() {
  net, _ := net.Dial("tcp", "127.0.0.1:9988")
  go clientBroadcast(net,"123456789101112")
  go clientBroadcast(net,"do dododo do dodo do")
  go clientBroadcast(net,"123456789101112")
  go clientBroadcast(net,"do dododo do dodo do")
  go clientBroadcast(net,"123456789101112")
  go clientBroadcast(net,"TWELVE!")
  time.Sleep(100 * time.Millisecond)
  go clientBroadcast(net,"YOU'LL NEVER SEE ME!")
}

The server receives them and prints them out:

func serverBroadcast(con net.Conn, ch chan string) {
  buf := make([]byte, 1024)
  bytenum, _ := con.Read(buf)
  strin := string(buf[0:bytenum])
  fmt.Printf("
 Server Broadcasting Message {%v}
",string(strin))
}

How is it that the server is apparently receiving all 4 messages at once and not one at a time?

I'm getting this message:

Server Broadcasting Message {123456789101112do dododo do dodo do123456789101112do dododo do dodo do123456789101112TWELVE!}

Server Broadcasting Message {123456789101112do dododo do dodo do123456789101112do dododo do dodo do123456789101112TWELVE!}

Server Broadcasting Message {123456789101112do dododo do dodo do123456789101112do dododo do dodo do123456789101112TWELVE!}

However I would have assumed I should have received this (in some random order as they are all threaded)

Server Broadcasting Message {123456789101112}

Server Broadcasting Message {do dododo do dodo}

Server Broadcasting Message {123456789101112}

Server Broadcasting Message {do dododo do dodo}

Server Broadcasting Message {TWELVE!}

Server Broadcasting Message {123456789101112}

Server Broadcasting Message {do dododo do dodo}

Server Broadcasting Message {123456789101112}

Server Broadcasting Message {do dododo do dodo}

Server Broadcasting Message {TWELVE!}

Server Broadcasting Message {123456789101112}

Server Broadcasting Message {do dododo do dodo}

Server Broadcasting Message {123456789101112}

Server Broadcasting Message {do dododo do dodo}

Server Broadcasting Message {TWELVE!}

Answer 1

The problem is that in this function you aren't reading all the data available on the stream. You'll need to call Read more than once to get all the data.

func serverBroadcast(con net.Conn, ch chan string) {
    buf := make([]byte, 1024)
    bytenum, _ := con.Read(buf)
    strin := string(buf[0:bytenum])
    fmt.Printf("
 Server Broadcasting Message {%v}
", string(strin))
}

However if you do that you'll find it will block, (playground), eg

func serverBroadcast(con net.Conn, ch chan string) {
    buf := make([]byte, 1024)
    for {
        bytenum, err := con.Read(buf)
        if err != nil {
            fmt.Printf("Err %v", err)
            return
        }
        strin := string(buf[0:bytenum])
        fmt.Printf("
 Server Broadcasting Message {%v}
", string(strin))
    }
}

You need to delimit your messages over TCP, or send a count before the message so know where the messages start and end if you want to avoid blocking