Concurrency issues while reading and writing data in loop in TCP client server

Question

I was trying to create a client server model to learn some stuff and I just tried sending(writing) data from client to server in a loop and it just don't worked well. I think that there are some concurrency issues and the client writes faster to server and the server than read multiple statements in one go. How can I maintain this concurrency so that only one statement written by the client at a time is read by the server. Here is the code to illustrate the problem in a better.

Here is the server handleConnection Function

func main() {

    conn, err := net.Listen("tcp", ":8080")
    if err != nil {
        log.Println("Error:", err)
    }

    for {
        ln, err := conn.Accept()
        if err != nil {
            log.Println("Error:", err)
            continue
        }

        go handleConnection(ln)
    }

}

func handleConnection(conn net.Conn) {
    buffer := make([]byte, 4096)

    for i := 0; i < 10; i++ {
        n, err := conn.Read(buffer)
        if err != nil {
            fmt.Println(err, i)
        }

        fmt.Printf("%s\n", buffer[:n])
    }

    fmt.Println("Done")

    conn.Close()
}

Here is the client writing data to server in loop.

func main() {
    conn, err := net.Dial("tcp", ":8080")
    if err != nil {
        log.Println("Error:", err)
        os.Exit(1)
    }

    for i := 0; i < 10; i++ {
        _, err = conn.Write([]byte("Rehan"))
        if err != nil {
            fmt.Println(err, i)
        }
    }

    fmt.Println("Done")
    conn.Close()
}

This is the output by the server. ![This is the Server output ]1

Please don't use images of text. They are hard to read, and impossible for the visually impaired to read. They also can't be indexed or searched. Instead, just copy and paste the text directly into your post. — Jonathan Hall, Oct 29 '19 at 11:32

score 2 · Answer 1 · answered Oct 29 '19 at 11:32

2

It isn't a concurrency issue. It's a networking issue.

TCP is a stream protocol, as such, a single read() from a socket doesn't correspond to a single write() from the other side.

Instead, reads return whatever is in the TCP buffer at the time of read, regardless whether it was sent by a single call to write() or a hundred.

If you want to read the data from the socket as separate messages, you need a way of separating them by using a delimiter, counting bytes, or some other method.

answered Oct 29 '19 at 11:32

Malt

28,965
9
65
105

Thankyou Malt. It was quite helpful. – Muhammad Rehan Javed Oct 29 '19 at 11:37
Usually you use fix size message and padding when ever the message is short. Then on the server you read the right length. In your case `buffer := make([]byte, 5)` will get you the result you expect. – ZAky Oct 29 '19 at 12:05

Concurrency issues while reading and writing data in loop in TCP client server

1 Answers1

Linked