什麽是 STUN 伺服器?

STUN（用戶資料報協定[UDP]簡單穿越網路位址轉換器[NAT])


伺服器允許所有的NAT客戶終端(如防火牆後邊的電腦)與位於局區域網以外的VOIP服務商實現電話通話。

通過STUN伺服器，客戶終端可以瞭解他們的公共位址、擋在他們前面的NAT類型和通過NAT與特定局部埠相連的因特網方埠。


這些資訊將被用於建立客戶終端與VOIP服務商之間的UDP通信，以便實現通話。STUN協定在RFC 3489中予以定義。

雖然是在UDP 埠3478連接STUN伺服器，但會暗示客戶終端在另外一個IP和埠號上實施測試（STUN伺服器有兩個IP位址）。RFC 規定這個埠和IP是隨意的。

-----原文----

A STUN (Simple Traversal of User Datagram Protocol [UDP] Through Network Address Translators [NATs]) 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 and so establish a call. The STUN protocol is defined in RFC 3489.

The STUN server is contacted on UDP port 3478, however the server will hint 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 are arbitrary.