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Adrian Georgescu, 12/10/2009 08:29 am

= Library Features =

<acronym title="WikiStart, Sip*, depth=2">TOC</acronym>

SIP SIMPLE client is a Software Development Kit for easy development of Real Time Applications based on SIP and related protocols for Presence, Audio, Instant Messaging (IM), File Transfers and Desktop Sharing. Other media types can be easily added by using an extensible high-level API.

The software has undergone in the past years several interoperability tests at [http://www.sipit.net SIPIT] and today is of industry strength quality.

General Features * Written in Python programming language * Non-blocking Asynchronous Design * Event Driven Application Programming Interface * TLS Security for both signaling (SIP) and media planes (MSRP, XCAP) * Failover for DNS lookups, SIP next hop routing and MSRP relay reservation * Multiple SIP Accounts Support * Multiple Media Types per session (e.g. Audio + Instant Messaging + Desktop Sharing) * Multiple Active Sessions support with add/remove of media within same session * Trace Capability for underlying protocols * Compatible with SIMPLE functionality of OpenSIPS and OpenXCAP servers

The library has cross platform capabilities on Linux OS, Mac OSX (Leopard and Snow Leopard) and Microsoft Windows (roadmap). The library should work with minimal changes on any platform that supports C and Python development environments.

Location Discovery * [http://tools.ietf.org/html/rfc3263 RFC3263] next hop resolution lookup * Bonjour multicast DNS [http://tools.ietf.org/html/draft-lee-sip-dns-sd-uri-03] (not implemented yet) * Other lookup mechanisms can be easily added (e.g. P2PSIP or DHT)

The library uses a separated from the core lookup mechanism for the next hop routing. This important feature allows the library to be used for building SIP clients that operate in combination with any SIP provider (by employing RFC 3263 DNS lookups), in a server-less LAN operation (using Bonjour protocol) or integrated into a network overlay developed by a third party (e.g. P2PSIP overlay).

SIP Transport * Automatically handles changes of System IP Address * Session Initiation Protocol [http://tools.ietf.org/html/rfc3261 RFC3261] * Support for UDP, TCP and TLS transports SDP Negotiation * Session Description Protocol [http://tools.ietf.org/html/rfc4566 RFC4566] * An Offer/Answer Model with Session Description Protocol (SDP) [http://tools.ietf.org/html/rfc4566 RFC4566] * Support of re-INVITE for adding and removing media streams

Supported media types:

  • Audio/VoIP (RTP/sRTP with or without ICE and STUN)
  • Instant Messaging over MSRP (with or without MSRP relay support)
  • File Transfer over MSRP (with or without MSRP relay support)
  • Desktop Sharing (VNC over MSRP)

All media types can be combined together in the same SIP session.

NAT Traversal

The client library supports the best NAT traversal techniques available today:

Audio * A Transport Protocol for Real-Time Applications [http://tools.ietf.org/html/rfc3550 RFC3550] * Real Time Control Protocol (RTCP) attribute in Session Description Protocol (SDP) [http://tools.ietf.org/html/rfc3605 RFC3605] * Generation and parsing of RFC 2833/telephone-events payload in both RTP and SDP [http://tools.ietf.org/html/rfc2833 RFC2833] * The Secure Real-time Transport Protocol (SRTP) [http://tools.ietf.org/html/rfc3711 RFC3711] * Echo cancelation control * Hold * DTMF tone generator * Conference bridge * Wav player and recorder * RTP timeout detection * Codecs: speex, g711, ilbc, gsm, g722 Presence

All features have been built-in and tested with [http://opensips.org OpenSIPS] Presence Agent.


All features have been built-in and tested with [http://openxcap.org OpenXCAP] server.

Instant Messaging * Common Presence and Instant Messaging (CPIM): [http://tools.ietf.org/html/rfc3862 RFC 3862] * Session Initiation Protocol (SIP) Extension for Instant Messaging [http://tools.ietf.org/html/rfc3428 RFC3428] * MSRP protocol [http://tools.ietf.org/html/rfc4975 RFC4975] * Indication of Message Composition for Instant Messaging [http://tools.ietf.org/html/rfc3994 RFC3994] * Message summary event package [http://tools.ietf.org/html/rfc3842 RFC3842] (not implemented yet) File Transfer * MSRP file transfer [http://tools.ietf.org/html/rfc5547 RFC5547] (partial sending not implemented yet) Desktop Sharing * Variation of [http://tools.ietf.org/html/draft-garcia-mmusic-sdp-collaboration-00 draft-garcia-mmusic-sdp-collaboration-00] using RFB over MSRP Conferencing * Conference event package [http://tools.ietf.org/html/rfc4575 RFC4575] (not implemented yet) * MSRP ad-hoc multi-party chat sessions [http://tools.ietf.org/html/draft-ietf-simple-chat-05 draft-ietf-simple-chat-05] (not implemented yet)