Just sharing the link here, since I was googling for far too long to dig it out.

How To Use STUN In Applications

It’s surprising this is found as a part of the manual for Maemo, the fantastic OS that moved in the right direction, but was practically abandoned by Nokia.

NOTE: This is apparently a guide for the outdated libjingle 0.3.0. I can’t find any guide for the new version of libjingle.