How can i measure my local server's response time?

Question

I am using a server-client based architecture with sockets in java on my localhost and I need to know how much it takes my localhost to send a response, any ideas on how I can measure that? (i am using 2 separate classes for listening to the keyboard and the server at the same time) This is my Clients main function:

public static void main(String[] args) throws IOException {

    Socket socket = new Socket(SERVER_IP,SERVER_PORT);
    ServerConnection connection = new ServerConnection(socket);

    BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in));
    PrintWriter out = new PrintWriter(socket.getOutputStream(),true);

    new Thread(connection).start();

    while(true){
        String command = keyboard.readLine();
        if(command == "quit"){
            break;
        }
        out.println(command);
    }

    socket.close();
    System.exit(0);
}

This is my server connection class's run method where I listen to te server.

@Override
    public void run() {
            String res = null;
            try {
                while (true) {
                    res = in.readLine();
                    if (res==null) break;
                    System.out.println("Server>: " + res);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }finally {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

so in other words I am sending the request from one class and receiving it in another class.