Question

I have a file transfer applet, and I am at the moment creating a logging system, so in the applet as it initialized, until it send file and finish will start printing a log file (originally it goes to java console on the client side) but now I’m modifying it so it will go to the server instead (create a file in the server and start writing on the file).

It working now, I’m using port 5000, but I need to open the firewall for port 5000 since opening port is dangerous, can I just use port 80 or 443 (HTTPS) since it open anyway for file transfer? how to do it?

example of the code at the moment is

in java applet there will be

handler = new SocketHandler("xxx.xxx.xxx.xx", 5000);
//on different area of the file there will be something like
log("starting the applet");
log("sending email");
...

while on the server I create a simple java server like this

public class ThreadedEchoServer {
    // using port 5000 
    static final int PORT = 5000;

    public static void main(String args[]) {
        ServerSocket serverSocket = null;
        Socket socket = null;

        try {
            serverSocket = new ServerSocket(PORT);
        } catch (IOException e) {
            e.printStackTrace();

        }
        while (true) {
            try {
                socket = serverSocket.accept();
            } catch (IOException e) {
                System.out.println("I/O error: " + e);
            }

            // new thread for a client
            new EchoThread(socket).start();
        }
    }
}

Answer 1

You really should not think about using ports 80 and 443 – these are ports for RECEIVING connections. After a connection is picked up on one of these ports the request is actually redirected to another port for handling. Therefore, using them to write will block any incoming communications.