Read Data from a Java Socket

Question

I have a Socket listening on some x port.

I can send the data to the socket from my client app but unable to get any response from the server socket.

  BufferedReader bis = new BufferedReader(new 
  InputStreamReader(clientSocket.getInputStream()));
  String inputLine;
  while ((inputLine = bis.readLine()) != null)
  {
      instr.append(inputLine);    
  }

.. This code part reads data from server.

But I cant read anything from server until unless the Socket on the server is closed. Server code is not under my control to edit something on it.

How can I overcome this from client code.

Thanks

Answer 1

Looks like the server may not be sending newline characters (which is what the readLine() is looking for). Try something that does not rely on that. Here's an example that uses the buffer approach:

    Socket clientSocket = new Socket("www.google.com", 80);
    InputStream is = clientSocket.getInputStream();
    PrintWriter pw = new PrintWriter(clientSocket.getOutputStream());
    pw.println("GET / HTTP/1.0");
    pw.println();
    pw.flush();
    byte[] buffer = new byte[1024];
    int read;
    while((read = is.read(buffer)) != -1) {
        String output = new String(buffer, 0, read);
        System.out.print(output);
        System.out.flush();
    };
    clientSocket.close();

Answer 2

To communicate between a client and a server, a protocol needs to be well defined.

The client code blocks until a line is received from the server, or the socket is closed. You said that you only receive something once the socket is closed. So it probably means that the server doesn't send lines of text ended by an EOL character. The readLine() method thus blocks until such a character is found in the stream, or the socket is closed. Don't use readLine() if the server doesn't send lines. Use the method appropriate for the defined protocol (which we don't know).

Answer 3

For me this code is strange:

bis.readLine()

As I remember, this will try to read into a buffer until he founds a '\\n' . But what if is never sent?

My ugly version breaks any design pattern and other recommendations, but always works:

int bytesExpected = clientSocket.available(); //it is waiting here

int[] buffer = new int[bytesExpected];

int readCount = clientSocket.read(buffer);

You should add the verifications for error and interruptions handling too. With webservices results this is what worked for me ( 2-10MB was the max result, what I have sent)

Answer 4

Here is my implementation

 clientSocket = new Socket(config.serverAddress, config.portNumber);
 BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));

  while (clientSocket.isConnected()) {
    data = in.readLine();

    if (data != null) {
        logger.debug("data: {}", data);
    } 
}