Java/android socket.close() is not realized by server

Question

I'm having an issue trying to get a java server to realize an (android/java) client has closed a TCP socket connection. I figured when the client calls close() on the socket , the server would catch an IOException , but this is not the case. t_recv is a thread that receives from BufferedReader in , and t_send sends using a PrintWriter out . Closing in causes a timeout and crash, and closing out doesn't really seem to do anything. The PrintWriter is created in the contructor of the t_send thread, and BufferedReader is create in the contructor of the t_recv thread. Trying to debug this, I created blank run() methods in both threads, and the same behaviour occurs.

An interesting note: the client is an Android application, and whenever the emulator freezes and windows has to force close it, the IOException is caught in the server and the "User xxxx left" message is displayed.

Client closing connection:

try {
    // t_recv.in.close(); - times out and crashes
    // t_send.out.close(); - appears to do nothing
    socket.close();
} catch (IOException e) {
    e.printStackTrace();
}

Server waiting for client to disconnect:

    for (;;)
    {   
        try {
            while ( (msg = in.readLine()) != null)
            {
                response = msg;
                System.out.println(response);
                server.broadcast(response);
            }
        } catch (IOException e) {
            System.out.println("User '" + socket.getInetAddress().toString() + "' left");
            try {
                socket.close();
                out.close();
                in.close();
            } catch (IOException e1) {
                e1.printStackTrace();
                System.exit(-1);
            }
            break;
        }
    }

Thanks for your time.

Answer 1

Assuming that in is a BufferedReader, the error is in this line:

    while ( (msg = in.readLine()) == null);

That will loop for ever if in is currently at the EOF. It should be:

    while ( (msg = in.readLine()) != null);

See javadoc for BufferedReader.readLine() , paying specific attention to the conditions in which it returns null .