STUN Server

The StunServer contains an example of how to create a basic STUN server.

The example uses "classic STUN" as specified in RFC3489.

The example program can be tested with a STUN client. If using Ubuntu or Windows Subsystem for Linux (WSL) the shell commands below demonstrate how to test the STUN server:

$ sudo apt install stun-client
$ stun 127.0.0.1
STUN client version 0.97
Primary: Open
Return value is 0x000001

It's not useful to run the STUN server on the same network as the client. Placing the STUN server on an external host results in:

$ stun 67.222.131.146
STUN client version 0.97
Primary: Independent Mapping, Port Dependent Filter, random port, no hairpin
Return value is 0x000016

An alternative Windows only test program is WinStun. It's somewhat old but since STUN is a very simple protocol it still works correctly. The results of testing WinStun with the demo program:

Nat with Independend Mapping and Port Dependent Filter - VoIP will work with STUN
Does not preserve port number
Does not supports hairpin of media
Public IP address: 37.228.xxx.xxx