SIP Communicator is a instant messenger client. A Java VoIP and Instant Messaging client. SIP Communicator is an audio/video Internet phone and instant messenger that supports some of the most popular instant messaging and telephony protocols such as SIP, Jabber, AIM/ICQ, MSN, Yahoo! Messenger, Bonjour, IRC, RSS and counting.

1. Audio and Video calls with SIP
2. Instant messaging with Jabber, ICQ/AIM, Yahoo! Msngr and MSN
3. IPv6 support for SIP and Jabber
4. Support for multiple accounts and meta contacts
5. Basic NAT & Firewall Traversal with STUN.
6. Modularity, extensibility, and flexibility with OSGi
7. Platform specific installers for Windows, Debian, Fedora, Mac OS X

Features Currently in Progress
1. Powerful and scalable firewall support -Combine technologies like TURN, STUN, ICE and P2P in order to achieve strong, secure, and scalable firewall support.
2. Robust and Seamless IPv6 support -We aim to achieve more than a mere "support for IPv6". We would like to guarantee its transparent and seamless usage. In other words, usage of IPv6 should not require any special configuration and should not cause any problems.
3. Security -Encrypt all media. Usage of P2P for firewall traversal imposes reliable security of all media transmitted by the SIP Communicator in order to prevent relaying nodes from eavesdropping.
4. Automatic updates and one-click plug-in installation -Provide a user interface and an online repository for SIP Communicator plug-ins.
5. Other plug-ins -IRC, shared whiteboards, multiparty video and chat conferencing.

Requirements:
* Java

The license of this software is Free, you can free download and free use this instant messenger software.