Question

I’m trying to send data from client socket to the server but, when data is sent, server is still waiting for data, after this the client socket then waiting for a data from server. There are two sockets waiting each other. Could someone explain what is wrong:

Client:

package ssd8ex3_tcp_client;

import java.io.*;
import java.net.*;

public class Ssd8Ex3_TCP_Client {

    private static final int SERVICE_PORT = 2000;

    public static void main(String[] args) {

        String hostname = "localhost";

        int counter = 0;
        while (counter < 1000) {
            try {
                Socket socket = new Socket(hostname, SERVICE_PORT);
                socket.setSoTimeout(50000);
                PrintStream pstream = new PrintStream( socket.getOutputStream() );
                pstream.print(counter);
                pstream.flush();

                BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                String s = reader.readLine();
                System.out.println("Results :" + s);
                socket.close();

            } catch (IOException e) {
                e.printStackTrace();
            }

            counter++;
        }

    }
}

Server:

package ssd8ex3_tcp_server;

import java.io.*;
import java.net.*;


public class Ssd8Ex3_TCP_Server {

    public static final int SERVICE_PORT = 2000;

    public static void main(String[] args) {
        try {
            ServerSocket server_socket = new ServerSocket(SERVICE_PORT);

            System.out.println("Server started");

            for(;;){
                Socket nextClient = server_socket.accept();
                System.out.println("Received request from " + nextClient.getInetAddress() + ":" + nextClient.getPort());

                BufferedReader reader = new BufferedReader(new InputStreamReader(nextClient.getInputStream()));
                String s = reader.readLine();
                OutputStreamWriter out = new OutputStreamWriter(nextClient.getOutputStream());
                PrintWriter pout = new PrintWriter(out);

                pout.print(s);

                out.flush();

                nextClient.close();
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Answer 1

Your server uses readLine, which will wait for a complete line. Your client uses print which doesn’t append an end-of-line marker. So the server is waiting for that end-of-line.

Use println in the client (and do the same for the return exchange), and things should get “unstuck”.