Published on iptel.org (http://www.iptel.org)

SIP Express Media Server

By Stefan
Created 2006-10-12 14:14
This is the homepage of SEMSi [1], the SIP Express Media Server. SEMS is a free, high performance, extensible media and application server for SIP (RFC3261) based VoIPi [2] services.

SEMS is a media and application server for SIP based VoIP services. It shows good performance doing basic services like announcements and conference for combination with external application servers, and, thanks to its easy to use and flexible application development framework and back-to-back user agent support, application logic and media serving can be combined in the same process. It can provide a full VoIP system together with SIP Express Router (SER) [3]/Kamailio [4], and has a flexible but powerful SBC (B2BUAi [5]) application included. Basic applications like announcement, pre-call announcement, RBT, conference, voicemail, mailbox etc. and lots of example applications available. Scripting in python and a simple state machine description language. Support for all commonly used free codecs (g711, gsm, iLBCi [6], speex, adpcm, l16 etc), wideband, ZRTP encryption, SIP registrar client, XMLRPC server/client, DIAMETERi [7] client and more.

SEMS is free software (speech+beer), it is licensed under dual license terms: the GPLv2+ [8] and proprietary license [9].

Some SEMS use cases (in blue):

  SEMS 1.6.0 Release (06/16/15)
  This release (source via ftp [14], source via http [15], gh [16]) of the SIP Express Media Server features tons of powerful SBC functionalities, like transcoding, registration caching, control of routing via external data sources like redis or MySQL DBs or XMLRPC servers, DSM-scriptable call control for managing simple to complex call flows including multiple call legs, among many others. Many Thanks to all contributors, and especially to the main sponsors of SEMS development, FRAFOS GmbH and Sipwise GmbH.

  New debian packages repositoryi [17] available (1.5 plus nightlies) (04/13/14)
  Thanks to Victor Seva from the Sipwise team there's now a debian package repository [18] available with packages of 1.5 and master branches (including nightly builds).

  SEMS at KamailioWorld 2014 (04/02/14)
  SEMS is present with a workshop on day 1 [19] and a short talk on day 3 [20] at KamailioWorld 2014 [21].

  SEMS 1.5.0 released (07/06/12)
  SEMS 1.5.0 is available (source [22], Debian/Ubuntu packages [23], OBS page [24], changelog [25]). This release includes a lot of new features such as wideband support with dynamic resampling, complete rework of the offer/answer code, as well as a lot of small improvements and many new DSM modules.
  SEMS at LinuxTag 2012 on 23.-26. May (05/16/12)
  The SEMS project will be this year again at LinuxTag [26], 23rd to 26th of May in Berlin, Germany. We will be together with the friends from the Kamailio project in both 7.2b 278, next to the Open Source Arena, and happy to meet you there!

  SEMS 1.4.3 released (05/04/12)
  SEMS 1.4.3 is available (source [27], Debian/Ubuntu packages [28], OBS page [29], changelog [30]). This release in the 1.4 series fixes a few mostly smaller and specific issues, and should be a drop-in replacement for SEMS 1.4 installations.

  SEMS at FOSDEM 2012 (4th/5th Feb 12)
  SEMS will be present at the FOSDEM 2012 [31] conference with some core developers. We will be around at the social event on Saturday 4th [32], and a talk about the SEMS SBC [33] (slides [34], info [35]) is scheduled for Sunday 5th at 12:35 at the Telephony and Communications Devroom in H.2213 [36].

  Talks about SEMS SBC and SEMS RTMP gateway (09/03/11)
  At the 10 years SER conference [37] (lanyrd [38]), there were two talks about SEMS for which the slides are now available: SEMS SBC [39] (Stefan Sayer) and SEMS RTMP Gateway [40] (Raphael Coeffic).

  SEMS 1.4.2 released (08/25/11)
  SEMS 1.4.2 is available (source [41], Debian/Ubuntu packages [42], OBS page [43], changelog [44]). This release in the 1.4 series fixes a few issues, including authentication for BYE requests, proper CODEC filter for unnamed codec with static payloads, and SIP auth qop header format.

  SEMS 1.4.1 released (05/24/11)
  SEMS 1.4.1 is available (source [45], Debian/Ubuntu packages [46], OBS page [47]). This release in the 1.4 series fixes various issues, among them support for rfc2617 qop auth, more than 1024 connections for XMLRPC, and several SIP related issues. Upgrade to this version is recommended for all users of SEMS, and as it is a drop in replacement for 1.4.0, especially for the users of 1.4.0. See the release's changelog [48] for details.

  SEMS 1.4.0 released (03/15/11)
  SEMS 1.4.0 is available (source [49]). This release features a powerful SBC module, adds multihoming support, and extends the DSM language to become a more fully featured language for app logic implementation. Furthermore, MWI through PUBLISH has been added, many bugs have been fixed, and performance has been improved yet again. See the changelog [50] for more details.

   Current source packages:
  • SEMS 1.6.0 [51], 1.5.0 [52], 1.4.3 [53], 1.4.2 [54], 1.3.1 [55], 1.2.1 [56], 1.1.1 [57], 1.0.1 [58]
   All versions:

  • SEMS download area: ftp://ftp.iptel.org/pub/sems/ [59]
   Binary packages for your Distribution:
  • current Debian/Ubuntu packages at https://pkg.opensbc.org/ [60], see the instructions on that page.
  • older versions' Debian/Ubuntu packages at Opensuse Build Service (OBS) [61]: Installation instructions [62]. E.g. for Debian lenny, add
     deb http://download.opensuse.org/repositories/home:/team-semsi [63]/Debian_5.0 ./ 
    to your sources.list (without the small i). Then run
     wget http://download.opensuse.org/repositories/home:/team-sems/Debian_5.0/Release.key -O - |apt-key add -  apt-get update && apt-get install sems 
  • RHEL/FC packages at EPEL [64]. Add EPEL to your server, then run
    yum install sems
   Source code Repository

SEMS is developed in a public git repository at GitHub: https://github.com/sems-server/sems [65].

  • git clone https://github.com/sems-server/sems.git
  • git clone ssh://github.com/sems-server/sems.git


Posting to mailing lists is 'member-only' to avoid spam, subscribe before posting.
  • Development: semsdev@iptel.org [66]. Links: Subscribe [67], archive [68]
  • Users: sems@iptel.org [69]. Links: Subscribe [70], archive [71]
  • SEMS issue tracker at github [72]


  • The main SEMS documentation page [73]
  • A somewhat old introduction to SEMS (slides) [74].
  • The README [75]
  • Documentation [76] accompanied with the source
Developer documentation quick links
  • Design overview (pdf) [77]
  • SEMS application development tutorial [78]
  • slides of a presentation centered on SEMS application development [79]
   SEMS is available under dual license terms: freely under GPL and under proprietary terms. Contact info@frafos.com for more information.

Source URL:
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