Socket multithreading programming DataInputStream.available() = 0 while outputstream writes correctly

Question

I used a socket in my client class and try to get a string from server that is written into DataOutputStream successfully. Below is the sample code.

try(Socket socket = new Socket(ip, port);)
    {
        // Output and Input Stream
        DataInputStream input = new DataInputStream(socket.getInputStream());
        
        DataOutputStream output = new DataOutputStream(socket.getOutputStream());       
        
        //receive message from server
        while(true && input.available() > 0)
        {
            String message = input.readUTF();
            System.out.println(message);
            TextArea.setText(message);
        }
        
    } 
    catch (UnknownHostException e)
    {
        e.printStackTrace();
    }
    catch (IOException e) 
    {
        e.printStackTrace();
    }

However, when my client wants to show that message in a TextArea. It appears that input.available()=0 so it doesn't show that message. But when I print out the message string, it's really confusing that it is the exact string I want. Finally I just get rid of the while-statement and directly use TextArea.setText(message) to show that message. Anyone can help me clarify that?

Answer 1

What protocol is the server expecting? If the server is expecting some request first (e.g. HTTP), you'll need to send a request before expecting any bytes sent in the input stream (a reason that input.available is 0).

See here for an example: https://www.infoworld.com/article/2853780/socket-programming-for-scalable-systems.html