Twinkle is a software phone for voice over IP communications using the SIP protocol. You can use it for direct IP phone to IP phone communication, or in a network using a SIP proxy to route your calls. Some of the features offered are call waiting, call hold, 3-way conference call, call transfer, and call reject. It supports STUN or a statically configured public IP address for NAT traversal. When using STUN, it will send keep-alive packets to keep NAT bindings alive. It supports ZRTP for secure voice communication. License: GNU General Public License (GPL) Changes:
This release adds support for TCP as a transport protocol for SIP. Twinkle now automatically discovers which local IP address to use when you make a call or register your user account. Furthermore, you can now send DTMF when an early media stream is set up during call setup.

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