Socket Programming: Java Client - Ruby Server

Question

I'm trying to socket connection between a Ruby Server and a Java Client. The connection is setup with success but I'm finding difficulties when sending a message from server to client.

This is how my Ruby Server looks like:

class ServerSocket 
  loop do
    server = TCPServer.new(ip, port).accept
    while server
      line = server.recv(65000)

      puts "Message: #{line}"

      server.flush

      server.puts("Hi from server!")

      server.flush
    end 
  end
end

When I try with this Java Client:

Socket socket = new Socket(InetAddress.getByName(ip), port);

PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
out.write("Hello from client!");

socket.close();

the connection is established and the message is sent with success from client to server. But when the server reaches this line:

server.puts("Hi from server!")

it throws this exception:

lib/server_socket.rb:11:in `write': Broken pipe (Errno::EPIPE)
    from lib/server_socket.rb:11:in `puts'
    from lib/server_socket.rb:11:in `block in <class:ServerSocket>'
    from lib/server_socket.rb:2:in `loop'
    from lib/server_socket.rb:2:in `<class:ServerSocket>'
    from lib/server_socket.rb:1:in `<top (required)>'
    from /home/dionis/.rvm/gems/ruby-2.4.1@sample/gems/railties-5.1.4/lib/rails/commands/runner/runner_command.rb:34:in `load'
    from /home/dionis/.rvm/gems/ruby-2.4.1@sample/gems/railties-5.1.4/lib/rails/commands/runner/runner_command.rb:34:in `perform'
    from /home/dionis/.rvm/gems/ruby-2.4.1@sample/gems/thor-0.20.0/lib/thor/command.rb:27:in `run'
    from /home/dionis/.rvm/gems/ruby-2.4.1@sample/gems/thor-0.20.0/lib/thor/invocation.rb:126:in `invoke_command'
    from /home/dionis/.rvm/gems/ruby-2.4.1@sample/gems/thor-0.20.0/lib/thor.rb:387:in `dispatch'
    from /home/dionis/.rvm/gems/ruby-2.4.1@sample/gems/railties-5.1.4/lib/rails/command/base.rb:63:in `perform'
    from /home/dionis/.rvm/gems/ruby-2.4.1@sample/gems/railties-5.1.4/lib/rails/command.rb:44:in `invoke'
    from /home/dionis/.rvm/gems/ruby-2.4.1@sample/gems/railties-5.1.4/lib/rails/commands.rb:16:in `<top (required)>'
    from bin/rails:9:in `require'
    from bin/rails:9:in `<main>'

Another user experience is when I try with this Java Client:

Socket socket = new Socket(InetAddress.getByName(ip), port);

PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
out.write("Hello from client!");


BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String serverMsg = in.readLine();

System.out.println("Server: " + serverMsg);

socket.close();

Here, I'm trying to get the message from the server. But when the client reaches this line:

String serverMsg = in.readLine();

it just hangs there forever.

Does anyone know how to deal with this?

EDIT (full client code)

ClientSocket.java

public class ClientSocket implements Runnable{

    @Override
    public void run() {
        System.out.println("Connecting...");
        try {

            Socket socket = new Socket(InetAddress.getByName(ip), port);

            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            out.write("Hello from client!");

            socket.close();

            System.out.println("Closing...");
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

Main.java

public class Main{

    public static void main(String[] args) {

        Thread cThread = new Thread(new ClientSocket());
        cThread.start();


    }

}

Answer 1

@Dionis I am not familiar with java. Have written a java client and ruby server I guess this will help you.

Ruby TCP server code:

require 'socket'
server = TCPServer.new(12345).accept
line = server.recv(50)
puts "Message from java Client: #{line}"
server.flush
server.puts("Hi from server!")
server.flush

Java TCP Client code:

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

class Main{

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

    Socket socket = new Socket("localhost", 12345);
    DataInputStream is = new DataInputStream(socket.getInputStream());
    DataOutputStream os = new DataOutputStream(socket.getOutputStream());
    os.writeBytes("Hello \n");
    String line = is.readLine();
    System.out.println("Msg from ruby Server :" + line);
    socket.close();
    }
}

Let me know if resolve the issue Thanks!