//***** Socket basics: first, "blocking" sockets

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

public class PortProbe {
    public static void main(String[ ] args) {
        if (args.length < 1) {
           System.err.println("Usage: PortProbe <IP address>");
           return;
        }
        String host = args[0];
        // port numbers for common services
        int[ ] ports = {
             7,     // ping
            13,     // daytime
            21,     // ftp
            23,     // telnet
            71,     // finger
            80,     // http
           119,     // nntp (news)
           161      // snmp
        };
        // Probe each port.
        for (int i = 0; i < ports.length; i++) {
            try {
                Socket sock = new Socket(host, ports[i]);
                System.out.println(host + " listening on port " + ports[i]);
                sock.close();
            }
            catch(UnknownHostException e) {
                System.err.println(e);
                return;
            }
            catch(IOException e) {
                System.out.println(host + " not listening on port " 
                    + ports[i]);
            }
        }
    }
}