STUN (Simple Traversal of UDP through NATs (Network Address Translation)) is a protocol for assisting devices behind a NAT firewall or router with their packet routing. RFC 5389 redefines the term STUN as 'Session Traversal Utilities for NAT'.

• - STUN enables a device to find out its public IP address and the type of NAT service its sitting behind.
• - STUN operates on TCP and UDP port 3478.
• - STUN is not widely supported by VOIP devices yet.
• - STUN may use DNS SRV records to find STUN servers attached to a domain. The service name is _stun._udp or _stun._tcp

For more information, please consult : http://www.voip-info.org/wiki/view/STUN

Here's a list of public STUN servers we have compiled:

stun.l.google.com:19302
stun1.l.google.com:19302
stun2.l.google.com:19302
stun3.l.google.com:19302
stun4.l.google.com:19302
stun01.sipphone.com
stun.ekiga.net
stun.fwdnet.net
stun.ideasip.com
stun.iptel.org
stun.rixtelecom.se
stun.schlund.de
stunserver.org
stun.softjoys.com
stun.voiparound.com
stun.voipbuster.com
stun.voipstunt.com
stun.voxgratia.org
stun.xten.com
stun01.sipphone.com
stun.fwdnet.net
s1.taraba.net 203.183.172.196:3478
s2.taraba.net 203.183.172.196:3478
s1.voipstation.jp 113.32.111.126:3478
s2.voipstation.jp 113.32.111.127:3478
numb.viagenie.ca
stun.stunprotocol.prg
stun.counterpath.com
stun.services.mozilla.com