| SIP express media server - README |
SEMS is a free, high performance, extensible media server
for SIP (RFC3261) based VoIP services.
It is intended to complement proxy/registrar servers
in VoIP networks for all applications where server-
side processing of audio is required, for example away
or pre-call announcements, voicemail, or network side
SEMS can be used to implement simple high performance
components like announcement servers as building
blocks of more complex applications, or, using its powerful
framework for application development including back-to-back
user agent (B2BUA) functionality, complex VoIP services
can be realized completely in SEMS.
The following applications are shipped with SEMS :
* announcement: plays an announcement
* voicemail: records voice messages and sends them
* conference: enables many people to talk together
at the same time
* webconference: conference application that can be
controlled from an external program,
e.g. a website
* echo: test module to echo the caller's voice
* mailbox: auto-attendant that saves voicemails into
an IMAP server. Users can dial in to check
* ann_b2b: pre-call-announcement, plays announcement
before connecting the callee in B2BUA mode
* announce_transfer: pre-call-announcement, plays announcement
and then transfers the caller to the callee
* early_announce: (pre-call) announcement using early media (183)
* conf_auth: collect a PIN number, verify it against an
XMLRPC authentication server and connects in
* pin_collect: collect a PIN, optionally verify it, and transfer
the call into a conference
alongside a set of example applications intended to help
development of custom services, including a calling card
application, a traffic generator, a component to control the
media server via XMLRPC, and announcements played from DB.
SEMS' core implements basic call and audio processing,
and loads plug-ins which extend the system. Audio
plug-ins enable new codecs and file formats,
application plug-ins implement the services' logic.
Other modules called component modules provide
functionality for other modules to use.
You can easily extend SEMS by creating your own plug-ins.
Applications can be written using the SEMS framework API
in C++, or in Python using an embedded python interpreter
of the ivr or py_sems modules.
SEMS only supports patent free codecs. That means that codecs
like g729 won't be supported. On the other hand, SEMS supports
all important patent free codecs out of the box (g711u, g711a,
GSM06.10, speex, G726 and iLBC). Integrating other codecs in SEMS
is very simple.
SEMS shows very good performance on current standard
PC architecture based server systems. It has sucessfully
been run with 1200 G.711 conference channels on a quad-core
Intel(R) Xeon at 2GHz (700 GSM, 280 iLBC channels). On the
other hand it also runs on very small devices - for example
small embedded systems like routers running OpenWRT, for which
of course the achievable channel count is not that high.
1. SER version 0.9.6-sems: SIP Epress Router (www.iptel.org/ser)
SEMS uses SER as its SIP stack. SEMS & SER communicate
through unix socket, which means that a SER instance is
mandatory on every host using SEMS.
2. Python version >= 2.3 for the ivr (embedded python interpreter)
and py_sems, optional
3. flite speech synthesizer for TTS in the ivr, optional
4. lame >= 3.95 for mp3 file output, optional
How to get started with SEMS:
To try out SEMS, the easiest is to get the bundle and install it:
tar xzvf sems-0.10.0-bundle.tar.gz ; cd sems-0.10.0-bundle
make install PREFIX=~/sems-0.10.0-install SERPREFIX=~/sems-0.10.0-install
This gets you the default set of applications installed in that
directory, and in the end prints the commands to start it.
You can also follow one of the tutorials
linked from the SEMS homepage
(e.g. http://www.iptel.org/howto_sems_voicemail).The Application
Modules Documentation page then gives an overview of the application
modules that come with SEMS
If you are interested in writing your own applications, the
application development tutorial is a good start
together with the design overview
(http://www.iptel.org/files/semsng-designoverview.pdf) and the example
1. Download SEMS
Download the source tarball from ftp://ftp.iptel.org/pub/sems,
or get the newest version through svn:
$ svn checkout svn://svn.berlios.de/sems/trunk
$ svn checkout http://svn.berlios.de/svnroot/repos/sems/trunk
2. Compile SEMS
$ make all
$ make install
Notice: you don't need to execute 'make install' if you want to
run SEMS from the source tree, but in this case some paths
in the config files will need to be adapted.
If you want to install to a different prefix than /usr/local,
For detailed instructions for some modules, have a look at
doc/COMPILING as well.
3. Look at the default configuration file whether it fits your need:
If you installed SEMS with 'make install', the configuration
is at '/usr/local/etc/sems/sems.conf'.
Else make your own using sems.conf.sample.
4. Get and start SER as SIP stack for SEMS:
To install the ser-0.9.6-sems into the directory /some/dir the
following commands can used:
$ wget http://ftp.iptel.org/pub/sems/ser-0.9.6-sems_src.tar.gz
$ tar xzvf ser-0.9.6-sems_src.tar.gz
$ cd ser-0.9.6-sems
$ make install PREFIX=/some/dir
With the install target install-ser-cfg, e.g. using
$ make install-ser-cfg SERPREFIX=/some/dir
you can install a general ser-sems.cfg which will work with
ser-0.9.6-sems and make SER to act only as SIP stack for SEMS, i.e.
direct every request to SEMS. Then
$ /some/dir/sbin/ser -f /some/dir/etc/ser/ser-sems.cfg
runs SER on port 5070. This way, several versions of SER can be
used on the same server, e.g. a different version of SER as Registrar
5. Start SEMS:
If you installed SEMS with 'make install', sems can be
found at '/usr/local/sbin/sems'.
If you need help starting 'sems', try 'sems -h'.
6. Using SEMS
SEMS needs to be told from the many possible applications that are
loaded which one to run. You can simply set default_application
Another method is to append a header
P-App-Name: <app name>
to the INVITE, for example
In a typical SER-setup where an incoming INVITE should be
sent off to conference, the following lines can be executed in
the proxy's (!) ser.cfg (assuming the media server runs on the
same host with its SIP stack SER on port 5070):
A sample ser.cfg with which many applications can be tried is available
Alternatively, the SIP-stack-SER can be configured in ser-sems.cfg
to send all calls directly to one application, in that case the line
in ser-sems.cfg could be changed to e.g.
A sample ser.cfg file in this style can be found at
For more information please refer to doc/Configure-SEMS-Ser-HOWTO and
the SER User's guide.
Installed files using 'make install':
/usr/local/sbin/sems : SEMS executable
/usr/local/lib/sems/plug-in/* : plug-ins
/usr/local/lib/sems/audio/* : default path for audio files
/usr/local/lib/sems/ivr/* : precompiled IVR scripts
/usr/local/etc/sems/sems.conf : configuration file
/usr/local/etc/sems/etc/* : modules configuration files
/usr/local/share/doc/sems/README : this README.
source_path/scripts/sems[.redhat] : example start-up scripts.
source_path/sems.conf.example : example configuration file.
In the doc/ directory there is a set of files describing the
applications shipped with SEMS, alongside some more documentation.
Generate the doxygen documentation with 'make doc' in doc/doxygen_doc,
that contains all these files as well.
All this and more documentation is available online linked from
the SEMS homepage:
Support, mailing lists, bugs and contact:
Please have a look at the documentation and other information on
the SEMS homepage (www.iptel.org/sems).
Best-effort support is given through the mailing lists for SEMS,
firstname.lastname@example.org and email@example.com, which are the first address
to ask for help, report bugs and improvements. You need to be
subscribed to be able to post to the lists: http://lists.iptel.org.
The mailing list archives at http://lists.iptel.org/pipermail/sems/
and http://lists.iptel.org/pipermail/semsdev/ can be a great help as
well (especially with google site search on lists.iptel.org, e.g.
The bug tracker for SEMS is at http://tracker.iptel.org/browse/SEMS
Please submit all bugs, crashes and feature requests you encounter.
Raphael Coeffic (firstname.lastname@example.org), the father of SEMS,
Stefan Sayer (email@example.com), current lead developer,
and all contributors.
All kinds of contributions and bug fixes are very welcome, for
example new application or codec modules, documentation pages, howtos
etc. Please email one of the lists or the authors.
Special thanks goes to:
* Juha Heinanen
for numerous bug reports, improvements and contributions
* Ulrich Abend (firstname.lastname@example.org)
for his great debuging work and ISDN gateway which
unfortunately did not make it into this version yet.
* Jiri Kuthan (email@example.com)
for the debuging work and help to implement
the first communicating part between Ser & SEMS ('vm' module).
* iptego GmbH and iptelorg for sponsoring development and improvement
* All the others who helped during test session and reported bugs :-)
SEMS - the media-S in the SLAMP.