Java maintaining a persistent TCP connection

Question

I am trying to send multiple data from server to client using TCP. I want to create only one TCP connection for the entire session. How do I go about doing this?

I tried a code with the following flow, but the program stops after the first response is received.

Client side

1.create sockets and streams
2.send request for first data
3.wait for response from server
4.send next request <----------- server doesn't seem to handle this request
5.get next response from server

Server side

1.Create server socket and wait for incoming connections
2.Parse incoming request
3.Send response
4.Parse next request
5.Send next response

I do not close the sockets and streams on both sides while the session is alive.

Update Here is my code snippet: Client

public void processRequest() throws Exception {

    Socket tempSocket = new Socket("0.0.0.0", 6782);

    String requestLine = "This is request message 1" + CRLF;

    DataOutputStream outToServer = new DataOutputStream(tempSocket.getOutputStream());            
    BufferedReader inFromServer = new BufferedReader(new InputStreamReader(tempSocket.getInputStream())); 

    outToServer.writeBytes(requestLine + CRLF);

    String serverResponse = inFromServer.readLine();
    System.out.println(serverResponse);

    requestLine = "This is request message 2" + CRLF;

    outToServer.writeBytes(requestLine + CRLF);

    serverResponse = inFromServer.readLine();
    System.out.println(serverResponse);

    outToServer.close();
    inFromServer.close();
    tempSocket.close();
}

Server

public void processRequest() throws Exception {

    createConnections();

    String requestLine = inFromClient.readLine();
    System.out.println(requestLine);

    String responseLine = "This is the response to messsage 1";
    outToClient.writeBytes(responseLine + CRLF);

    requestLine = inFromClient.readLine();
    System.out.println(requestLine);

    responseLine = "This is the response to message 2";
    outToClient.writeBytes(responseLine + CRLF);
}

Output

Client:

This is the response to messsage 1
This is the response to message 2
BUILD SUCCESSFUL (total time: 1 second)

Server:

This is request message 1

null
java.net.SocketException: Broken pipe

Post the relevant code snippets -- it's hard to make suggestions on invisible code. :) — sarnold
– sarnold, Commented Mar 2, 2012 at 3:30
You wrote both sides, surely you can attach a debugger to the server and watch what happens when the second request arrives? — Jim Garrison
– Jim Garrison, Commented Mar 2, 2012 at 4:17
Have posted the necessary code snippets and the debugger output :) — shyamsundar2007
– shyamsundar2007, Commented Mar 2, 2012 at 16:54

Riza · Accepted Answer · 2012-05-11 19:38:01Z

2

I think the problem is in your client code. You wrote:

    String requestLine = "This is request message 1" + CRLF;
    .....
    outToServer.writeBytes(requestLine + CRLF);

You add CRLF to requestLine, and add it again when send it to server. Ensure that adding CRLF only once per message you want to send, it will behave as you want.

answered May 11, 2012 at 19:38

Riza

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1 Comment

shyamsundar2007 Over a year ago

Thanks a lot! that was indeed the problem with my code -.- Took me a couple of hours of debugging to find it out!

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