Question about port forwarding

[Infil]

I am building a C# application (or, more accurately, have already built) which can be thought of as an IRC-like chat room. A user runs my program in "server" mode and starts a lobby, running off a certain port. Other users start my program in "client" mode, and then connect to the lobby directly using the host's IP address and port.

The problem is, of course, port forwarding. There are good guides at portforward.com and the like, I understand, but I'm unsure of a few things. Namely, what about those people who would like to host a server and are on, say, a university network? Or what about those who are hooked up to a DSL modem or something where port forwarding is difficult or not possible? I have a friend in particular who is using an old cable box, and it does not look possible for him to host a lobby without going to a store and buying a router (which would, of course, limit the appeal of my program in the real world if this is a common problem).

I guess what I'm asking here is, is there a situation where a certain person simply will not be able to host, because he can't set up port forwarding properly due to restrictions at university or the like? I actually don't know how difficult it is to set up port forwarding in these cases, since I get my internet from a local provider, and we use a router to send it to all of our home machines (i.e., port forwarding is easy for me).

I should also specify that running a version of the program on a permanent server and have everyone connect to it, like IRC does, is not an option for me. I need to be able to connect peer-to-peer like this. Thanks for any help!

[johnwill]

For sure. If the network you are connecting through doesn't allow port forwarding, you're out of luck.

[Infil]

I see. And there's no real way around this, aside from building a program that runs on a dedicated server? It's just going to be impossible to directly connect to some computers?

But don't some other applications do this as well? Torrents and things like Kazaa come to mind?

[johnwill]

You can't connect to the computer unless the remote computer initiates the transfer. Take a look at TeamViewer for an example of how this works. Zolved remote control is another similar package. Note that you have to run a program on the remote machine to kick start the session.