Sending more than one request to a TCP server fails

Question

I'm trying to send more than one request to a TCP server in Go but for some reason the second request is never sent, even if it is identical to the first one.

This is the server:

func StartServer(host string) {

    l, err := net.Listen("tcp", host)
    log.Println("Starting server on:", host)

    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }

    defer l.Close()
    log.Println("Server is running...")

    for {
        // Listen for an incoming connection.
        conn, err := l.Accept()
        if err != nil {
            log.Fatal("Error accepting: ", err.Error())
        }
        // Handle connections in a new goroutine.
        fmt.Println("got a request")
        go handleRequest(conn)
    }
}

And this is the function in the client that sends the requests to the server:

func (u *User) ConnectToServer(host string, partner string) {
    conn, _ := net.Dial("tcp", host)
    fmt.Fprintf(conn, "message1\n")
    fmt.Fprintf(conn, "message2\n")
}

EDIT: In the handleRequest function I read the input as follows:

 // Handles incoming requests.
func handleRequest(conn net.Conn) {

    rec, err := bufio.NewReader(conn).ReadString('\n')

    if err != nil {
        log.Println("Error reading:", err.Error())
    }

    log.Println("Got message: ", rec)

    // Send a response back to person contacting us.
    conn.Write([]byte("Message received."))
    // conn.Close()
}

Which according to the documentation only takes the first part before the first line break detected so I believe the second message is ignored because of this. How can I read both messages? Should I change the delimiter in the client maybe?

Answer 1

The server should read multiple lines given that the client sends multiple lines. Use bufio.Scanner to read lines:

func handleRequest(conn net.Conn) {
   defer conn.Close()
   scanner := bufio.NewScanner(conn)
   for scanner.Scan() {
      fmt.Printf("Got message: %s\n", scanner.Bytes())
      conn.Write([]byte("Message received."))
   }
   if err := scanner.Err(); err != nil {
      fmt.Printf("error reading connection: %v\n", err)
   }
}

Some notes about the code:

• To prevent a resource leak, the function closes the connection on return.
• The scanner loop breaks on error reading the connection. If the error is not io.EOF, then the function logs the error.
• bufio.Reader can also be used to read lines, but bufio.Scanner is easier to use.