Added guide on setting up a TURN/STUN server

Tuleap: #641
Change-Id: I86718a10b03ab2281405f0c474281babdc7615ec

docs/source/index.rst

@@ -10,3 +10,4 @@ Contents:
    contributing
    compiling_and_installing/index
    releasing
+   setting_up_turn_stun

docs/source/setting_up_turn_stun.rst

+Setting up a TURN or STUN server
+================================
+
+Ring can be configured to use TURN or STUN servers (`RFC5766 <https://tools.ietf.org/html/rfc5766>`_) to establish a connection between two peers.
+
+In this guide, we will setup a `coturn <https://github.com/coturn/coturn>`_ server. There are other TURN/STUN server implementations available under a free license. See `TurnServer <http://turnserver.sourceforge.net/>`_ and `Restund <http://www.creytiv.com/restund.html>`_.
+
+1. Installing
+#############
+
+COTURN is available in most Linux distributions. On Debian, install it with the following command:
+
+.. code-block:: bash
+
+    apt-get install coturn
+
+2. Configuring
+##############
+
+Here is a basic ``turnserver.conf`` file:
+
+.. code-block:: none
+
+    listening-port=10000
+    listening-ip=0.0.0.0
+    min-port=10000
+    max-port=30000
+    lt-cred-mech
+    realm=sfl
+    no-stun
+
+3. Creating users on your TURN server
+#####################################
+
+To create users on your TURN server, use the ``turnadmin`` binary.
+
+.. code-block:: bash
+
+    turnadmin -a -u bob -p secretpassword -r sfl
+
+
+4. Launching the TURN server
+############################
+
+.. code-block:: bash
+
+    turnserver -c turnserver.conf
+
+
+5. Configuring Ring to authenticate to the TURN server
+######################################################
+
+You may configure Ring to use your TURN server from the advanced tab your account settings:
+
+============== ============================ ======================
+   Field                 Value                   Example
+============== ============================ ======================
+**server url** host and port of your server 0.0.0.0:10000
+**username**   username                     bob
+**password**   password                     secretpassword
+**realm**      realm                        sfl
+============== ============================ ======================