Test port on client

[Uncle Leo]

Hi,

I've written an application that uses a TcpClient to listen on a port.
Clients on other computers can then connect and start talking to each
other. The TcpClient listens on port 47141. Because this port is
closed by default on modem/routers, I want to build a webapplication
to test if a user has successfully opened or mapped a port on their
modem. The website is running on Framework 1.1. Any idea if this can
be done, and how?

Thanks,

Uncle Leo