Monthly Archives: February 2016


How to build and install FreeSWITCH 1.6 on Debian 8 Jessie

FreeSWITCH is an opensource telephony soft switch created in 2006. As per official wiki  page,

It is a scalable open source cross-platform telephony platform designed to route and interconnect popular communication protocols using audio, video, text or any other form of media.

Sounds good. right ?

We are using Debian for this tutorial as it is very stable & mature linux distribution and FreeSWITCH core developers’ choice-of-distribution .
You can read more about FreeSWITCH on there wiki page.

Now lets cut a crap & start an action, assuming you  already have working Debian 8 OS.

Build & Install FreeSWITCH

There are different ways to install FreeSWITCH. In this tutorial, we will see how to install it from source.

  1. First update your Debian box & install curl & git.
    apt-get update && apt-get install -y curl git
  2. Add FreeSWITCH GPG key to APT sources keyring.
    curl | apt-key add -
  3. Add FreeSWITCH repository to APT sources.
    echo "deb jessie main" > /etc/apt/sources.list.d/freeswitch.list
  4. Once again update your system.
     apt-get update
  5. Now lets first install FreeSWITCH dependencies.
    apt-get install -y --force-yes freeswitch-video-deps-most
  6. Though above step takes care of most of dependencies, few still remains required to compile mod_fsv. So install them as,

     apt-get install -y libyuv-dev libvpx2-dev
  7. Grab source code of FreeSWITCH as follows,
     git config --global pull.rebase true
     cd /usr/src/
     git clone freeswitch.git
  8. Now lets compile FreeSWITCH source for version 1.6
    cd freeswitch.git
     git checkout v1.6
     ./ -j
     ./configure -C
     make && make install
  9. Now lets compile sounds
    make all cd-sounds-install cd-moh-install
  10. Lets create simlinks to required binaries to access them from anywhere.
    ln -s /usr/local/freeswitch/bin/freeswitch /usr/bin/freeswitch
    ln -s /usr/local/freeswitch/bin/fs_cli /usr/bin/fs_cli


Set Owner & Permissions

cd /usr/local
groupadd freeswitch
adduser --disabled-password  --quiet --system --home /usr/local/freeswitch --gecos "FreeSWITCH Voice Platform" --ingroup freeswitch freeswitch
chown -R freeswitch:freeswitch /usr/local/freeswitch/
chmod -R ug=rwX,o= /usr/local/freeswitch/
chmod -R u=rwx,g=rx /usr/local/freeswitch/bin/

Starting FreeSWITCH service on boot automatically

To start FreeSWITCH after each boot automatically we need to set up init script. Init script is script used by init system to manipulate services. Debian 8 is now migrated to systemd init system, we will add systemd unit file.

Copy following content to ‘/lib/systemd/system/freeswitch.service’


; service
ExecStart=/usr/local/freeswitch/bin/freeswitch -u freeswitch -g freeswitch -ncwait -nonat -rp
; exec


Now execute following commands in your shell

chmod 750 /lib/systemd/system/freeswitch.service
ln -s /lib/systemd/system/freeswitch.service /etc/systemd/system/freeswitch.service
systemctl daemon-reload
systemctl enable freeswitch.service

Start FreeSWITCH

Now we are all set. Lets start hacking FreeSWITCH.

systemctl start freeswitch.service



  1. If something goes wrong & you try compilation again by ‘make clean’, sometimes you get errors regarding ‘spandsp’. To resolve them try to clean using
    ‘git clean -fdx’. For more info check this ticket –


Twisted Matrix

How to write port-forwarding program using Twisted

Recently I was faced with an issue where a long running process is listening on loop back IP ( on port 8080 on one of our servers and client programs on other machines are trying to access it on server’s local IP  We ended up at this situation when we have updated server configuration and restarted the server program and forgot to change IP binding info in config file from loop back to local IP. Server got busy with it’s work, with lots of customer’s connections already, by the time we have discovered that some services of  server are not accessible to client programs on other machines. So, the dummy’s guide to fixing it by changing config and restarting the server program is not an option as we can’t risk to disconnect existing customers. So, hot patching is the only option until we can restart the program at next scheduled down time.

I could have fixed this in couple of ways either by adding few lines to iptables configuration or by writing simple socket program in python. The task is to forward data coming in on local IP port 8080 to loop back IP ( port 8080 and send replies back to source address. Forwarding one socket data to other socket is pretty trivial using Python’s socket library and Twisted made it even more trivial, so I went with the following solution using Twisted.

__author__ = 'godson'

from twisted.protocols.portforward import ProxyFactory
from twisted.application import internet,service

src_ip = ""
src_port = 8080
dst_ip = ""
dst_port = 8080

application = service.Application("Proxy")
server = ProxyFactory(dst_ip, dst_port)
ps = internet.TCPServer(src_port,server,50,src_ip)


That’s it. Now, all I needed to do is to run this program by the following command

twistd -y

This simple program is made possible by the heavy lifting done by twisted library. Interested folks can look under hood at twisted’s module.