doupeng6890
2017-07-03 01:34
浏览 59
已采纳

Golang中带有TCP / IP套接字的通道不起作用

I just started writting a Golang client for a server that I've made in C with TCP/IP sockets, then I figured out that my channel wasn't working.

Any ideas why ?

func reader(r io.Reader, channel chan<- []byte) {
  buf := make([]byte, 2048)
  for {
    n, err := r.Read(buf[:])
    if err != nil {
        return
    }
    channel <- buf[0:n]
  }
}
func client(e *gowd.Element) {
 f, err := os.Create("/tmp/dat2")
 if err != nil {
    log.Fatal()
 }
 read := make(chan []byte)
 c, err := net.Dial("tcp", "127.0.0.1:4242")
 if err != nil {
    log.Fatal(err)
 }
 go reader(c, read)
 for {
    buf := <-read
    n := strings.Index(string(buf), "
")
    if n == -1 {
        continue
 }
 msg := string(buf[0:n])
 if msg == "WELCOME" {
    fmt.Fprint(c, "GRAPHIC
")
 }
 f.WriteString(msg + "
")
}

Testing my server with netcat results in the following output : http://pasted.co/a37b2954

But i only have : http://pasted.co/f13d56b4

I'm new to chan in Golang so maybe I'm wrong (I probably am)

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1条回答 默认 最新

  • dongxinyue2817 2017-07-03 02:03
    已采纳

    Channel usage looks alright, however retrieving value from channel would overwrite previously read value at buf := <-read since your waiting for newline.

    Also you can use bufio.Reader to read string upto newline.

    Your code snippet is partial so its not feasible to execute, try and let me know:

    func reader(r io.Reader, channel chan<- string) {
        bufReader := bufio.NewReader(conn)
        for {
            msg, err := bufReader.ReadString('
    ')
            if err != nil { // connection error or connection reset error, etc
               break
            }
            channel <- msg
        }
    }
    
    func client(e *gowd.Element) {
        f, err := os.Create("/tmp/dat2")
        if err != nil {
            log.Fatal()
        }
        read := make(chan string)
        c, err := net.Dial("tcp", "127.0.0.1:4242")
        if err != nil {
            log.Fatal(err)
        }
        go reader(c, read)
        for {
            msg := <-read
            if msg == "WELCOME" {
                fmt.Fprint(c, "GRAPHIC
    ")
            }
            f.WriteString(msg + "
    ")
        }
        //...
    }
    

    EDIT:

    Please find example of generic TCP client to read data. Also I have removed scanner from above code snippet and added buffer reader.

    func main() {
        conn, err := net.Dial("tcp", "127.0.0.1:4242")
        if err != nil {
            log.Fatal(err)
        }
    
        reader := bufio.NewReader(conn)
        for {
            msg, err := reader.ReadString('
    ')
            if err != nil {
                break
            }
            fmt.Println(msg)
        }
    }
    
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