Question

I’m learning about sockets in java. I was able to connect a client socket to an online server, but I can connect them to my own server socket!

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

class Blargh2 {
    public static void main(String[] args) {
        Socket client = null;
        ServerSocket server = null;
        System.out.println("Line one reacehd!");
        try {
            server = new ServerSocket(4445);
        } catch (Exception e) {
            System.out.println("Error:" + e.getMessage());
        }
        System.out.println("Line two reacehd!");
        try {
            client = server.accept();
        } catch (IOException e) {
            System.out.println("Accept failed: 4444");
            System.exit(-1);
        }

        System.out.println("Line three reacehd!");
        try {
            server.close();
            client.close();
        } catch (IOException e) {
            System.out.println("Accept failed: 4444");
            System.exit(-1);
        }
    }
}

The program reaches lines one and two but it never reaches line 3!
Can anyone help me solve this? Firewall also allows this connection…

Answer 1

It never reaches line 3 because you need a remote TCP socket (although it can be local, for testing) to connect to your socket on port 4445. You accept endpoint sockets on the server, which are used for communication with the remote client. There is actually no client here, so it waits indefinitely or until a timeout on the accept() call.