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Asked: 2026-05-25T13:31:55+00:00

Let’s say I have a server, and two clients connected to it. (via TCP,

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Let’s say I have a server, and two clients connected to it. (via TCP, but it doesn’t matter)

My goal is to allow a direct connection between those two clients. This is to allow direct voice contact between two players, for example, or any other client plugin they may have installed which don’t need server interaction (like playing some kind of random game between the two). The server can be there to help setting up the connection.

From duskwuff’s answer, I got several leads:

http://en.wikipedia.org/wiki/STUN which describes an algorithm to do that, and
http://en.wikipedia.org/wiki/UDP_hole_punching

From those, I got more leads:

http://www.h-online.com/security/features/How-Skype-Co-get-round-firewalls-747197.html
http://nutss.gforge.cis.cornell.edu/stunt.php — A possible STUN implementation with TCP

With time, I could surely work out something for my program. For now I’m using C++ and TCP (Qt Sockets or Boost sockets), but if needed I don’t mind doing UDP in C and wrapping it.

The bounty is there for any programmer having experience with those in C and C++ that may give tips to make this easier, by linking to example programs, updated libraries, or any other useful information. A documented, flexible & working C++ TCP implementation would be the best but I’ll take what I get!

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1 Answer

  1. Editorial Team

    Punching TCP holes in NAT is sometimes/often possible (it depends of the NAT behavior). This is not a simple subject to learn, but read the corresponding chapter about NAT traversal from Practical JXTA II (available online on Scribd) to understand the nature of the issues to solve.

    Then, read this. It comes from the guy who wrote that: http://nutss.gforge.cis.cornell.edu/stunt.php (one of the links in your question).

    I am not a C/C++ specialist, but the issues to solve are not language specific. As long as you have access to TCP from your code base, that’s enough. Keep in mind that implementing UDP traversal is easier than TCP.

    Hope these tips help.

    P.S.: I am not aware of a C/C++ implementation of the solution. The code mentioned in Cornell’s link is NOT operational as confirmed by the author. I tried to resuscitate it myself, but he let me know it was completely tweaked for research purposes and far from production ready.

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