Channels in Golang with TCP/IP socket not working

Question

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), "\n")
    if n == -1 {
        continue
 }
 msg := string(buf[0:n])
 if msg == "WELCOME" {
    fmt.Fprint(c, "GRAPHIC\n")
 }
 f.WriteString(msg + "\n")
}

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)

Answer 1

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('\n')
        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\n")
        }
        f.WriteString(msg + "\n")
    }
    //...
}

---

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('\n')
        if err != nil {
            break
        }
        fmt.Println(msg)
    }
}