Question

I am trying to write a small program, that opens a server, creates a client that connects to this server and receives a message from it.

This is the Code so far

public static void main(String[] args) {
final ServerSocket serverSocket;
try {
    serverSocket = new ServerSocket(12345);
    Thread t = new Thread(){
        public void run(){
                try {
                    Socket server = serverSocket.accept();
                    PrintWriter writer = new PrintWriter(server.getOutputStream(), true);
                    writer.write("Hello World");
                    writer.flush();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        };
        t.start();
        Socket client = new Socket("localhost", 12345);
        BufferedReader reader = new BufferedReader(new InputStreamReader(client.getInputStream()));
        String message = reader.readLine();

        System.out.println("Received " + message);
    } catch (IOException e1) {
        e1.printStackTrace();
    }

}

If i run program it keeps waiting in readLine() – so obviously the client does not receive the message from the server.
Has anyone got an idea why this isn’ working?

Answer 1

Your reading thread is waiting for a newline in the data stream. Just change the server to use:

writer.write("Hello World\r\n");

and you’ll get the result you were expecting. Alternatively, you can just close the server socket, and then readLine will return when it reaches the end of the data stream.