原文版权：copyright (c) the internet society (2003).? all rights reserved. 原文地址：http://midcom-p2p.sourceforge.net/draft-ford-midcom-p2p-01.txt
3.3. udp hole punching udp打洞技术
the third technique, and the one of primary interest in this document, is widely known as "udp hole punching." udp hole punching relies on the properties of common firewalls and cone nats to allow appropriately designed peer-to-peer applications to "punch holes" through the middlebox and establish direct connectivity with each other, even when both communicating hosts may lie behind middleboxes. this technique was mentioned briefly in section 5.1 of rfc 3027 [nat-prot], and has been informally described elsewhere on the internet [kegel] and used in some recent protocols [teredo, ice]. as the name implies, unfortunately, this technique works reliably only with udp.
