Thread: Creating a ServerSocket - Trying to save logs from a Wireless Linksys Router

Hello friends, I have written a program which opens up a socket on port 514. This is to accept and save logs from my wireless WAP54G router. I would like to eventually be able to use a buffered reader so I can stream the input into log files locally, but I can't seem to establish a connection. The connection eventually times out, and the program exits. Here is what I have:

import java.io.*;
import java.net.*;
 
public class KnockServer {
 
	public static void main(String args[]) {
 
		KnockServer server = new KnockServer();
		server.mainLoop();
	}
 
	public void mainLoop() {
 
		try {
			ServerSocket server = new ServerSocket(514);
			server.setSoTimeout(100000);
			System.out.println("Success!");
			while (true) {
				Socket connection = server.accept();
				BufferedInputStream in = new BufferedInputStream(connection.getInputStream());
				InputStreamReader inputReader = new InputStreamReader(in);
				StringBuffer process = new StringBuffer();
 
				connection.close();
				server.close();
			}
		}
		catch (IOException e) {
			System.out.println("Couldn't!");
			System.err.println(e.getMessage());
 
		}
		catch (SecurityException e) {
			System.err.println(e.getMessage());
		}
	}
}

Things to note: I am running Eclipse on Ubuntu. I am running the program with super user privileges. I have another program that somebody else has written in C, which opens up port 514 that does establish a connection, and I am able to see what the router is sending.

If anybody notices anything wrong with what I have written and could please give me a direction I would appreciate it. Also, if anybody else has any suggestions of what else it could be related to, that would be helpful as well.

Any exceptions raised? The timeout value is set, so if nothing is accepted by the ServerSocket during the timeout period a SocketTimeoutException should be thrown.

Sorry, I forgot to list the exception. After it times out, I do get a timed out exception:

Success!
Couldn't!
Accept timed out

There's your problem then - seems like nothing is coming from the other side. Are you sure that port is being used during the duration of the program execution?

Yeah it definitely is, I have a similar program written in C and it receives information and displays it in my terminal and log files. When I run this other program all I have to do is disconnect and reconnect to my network to get something sent from the router. When I do this in the program I am writing in Java nothing happens. This is why I am confused.

Thanks for your help, I was able to come up with a solution. The router was sending UDP packets, not TCP packets. Further, it was timing out because UDP differs from TCP in that UDP does not create a direct connection between the two, rather it sends data out into the network whether or not there is a receiving computer. This link explains the difference very well if anyone is interested. I implemented the DatagramSocket class which is designed for UDP and my program works great. Thanks again for the input, and here is the solution:

import java.io.*;
import java.net.*;
 
public class KnockServer {
 
	public static void main(String args[]) throws IOException {
 
		KnockServer server = new KnockServer();
		server.mainLoop();
	}
 
	public void mainLoop() throws IOException {
 
		DatagramSocket aSocket = null;
		try {
			aSocket = new DatagramSocket(514);
 
			System.out.println("Success, opened port 514...");
 
			byte[] buf = new byte[256];
 
			while (true) {
				DatagramPacket packet = new DatagramPacket(buf, buf.length);
				aSocket.receive(packet);
				System.out.println("Recieved a packet...");
				String sentence = new String(packet.getData());
				System.out.println(sentence);
			}
		}
		catch (IOException e) {
			System.err.println(e.getMessage());
 
		}
		catch (SecurityException e) {
			System.err.println(e.getMessage());
		}
		finally {
			aSocket.close();
		}
 
	}
}