Frequently Asked Questions

What is the definition of a STUN server?
Last Updated 6 years ago

  • A STUN (Simple Traversal of User Datagram Protocol [UDP] Through Network Address Translators [NAT]) server allows NAT clients (i.e. computers behind a firewall) to setup phone calls to a VOIP provider hosted outside of the local network.
  • The STUN server allows clients to find out their public address, the type of NAT they are behind and the internet side port associated by the NAT with a particular local port. This information is used to set up UDP communication between the client and the VOIP provider hence establishing a call. The STUN protocol is defined in RFC-3489.
  • The STUN server is contacted on UDP port 3478, however the server will direct clients to perform tests on alternate IP and port number too (STUN servers have two IP addresses). The RFC states that this port and IP must be arbitrary.

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