The SIP protocol relies upon being able to use DNS SRV records to locate SIP servers. The following resources may therefore be of use to implementers.
There is an implementation of the DNS protocol in Java including support for SRV records.
This code is released under the GNU Lesser General Public License (LGPL). This has implications for your software if you use it. See the GNU web site for licensing information.
Henning Schulzrinne, the co-author of SIP, maintains links to some DNS parsing libraries that may be helpful to C implementers: Port Assignments and DNS
RULI - RULI stands for Resolver User Layer Interface. It's a library built on top of an asynchronous DNS stub resolver. RULI provides an easy-to-use interface for querying DNS SRV resource records. The goal is to promote the wide deployment of SRV-cognizant software. RULI aims to fully support SRV-related standards. There are bindings for PHP and Perl. IPv6 is supported.
See also:
+ Codecs
+ Developers Programs and Community sites
+ Free SIP and ENUM Services
+ Commercial Service Providers
+ SIP Parsers and Stacks
+ Other Stacks, RTP Applications, code and bits and pieces
+ SIP and DNS
+ Testing Tools
+ Robustness testing
+ SIP Client Software, User Agents, Source Code
+ SIP Servers, Proxys and Gateways
+ SIP Drafts and RFC's
+ SIP Center links pages
+ Commercial SIP Products & Service Providers