Beremiz and Beremiz_service connectors 
======================================

To connect a PLC, Beremiz provides 2 types of connectors :
 * a Pyro connector
 * a WAMP connector

To configure the connection, you have to set the *URI_location* in your project Config tab according to this documentation. 

The Pyro connector
----------------------------

Pyro is an advanced and powerful Distributed Object Technology system written entirely in Python.
Beremiz_service spawns a Pyro server, serving a PLCObject (see runtime/PLCObject.py). Therefore, Beremiz acts as a Pyro client.

TODO:: link to PLCObject API documentation

URI_location :
 * LOCAL:// is a facility that starts the PLC service locally and connect Beremiz to it via Pyro.
   This is intended for use in development stage.
 * PYRO://<ip:port> normal connection to a remote PLC. PLC default port is 3000.
 * PYROS://<ip:port> SSL connection to a remote PLC, see below.

more information about Pyro can be found on http://pythonhosted.org//Pyro/1-intro.html

===========================
Setup a Pyro SSL connection
===========================

Pyro v3 has a limited TLS/SSL support based on m2crypto. Pyro v4 had dropped it.
In order to have a full and reliable SSL, we recommand to use a TLS/SSL wrapper as nginx, stub or stunnel.

--------------------
TLS-PSK with stunnel
--------------------

In this example, we setup a simple TLS-PSK connection according to rfc4279.
This ciphersuite avoid the need for public key operations and certificate management.
It is perfect for a performance-constrained environments with limited CPU power as a PLC.


Needed :
 * stunnel >= 5.09

verify openssl support for PSK cipher::

    openssl ciphers -v 'PSK'

----------------------
Client setup (Beremiz)
----------------------

You need to choose an identity for your client, here *client1*.
generate a valid and strong key::

    $ echo client1:$(openssl rand -base64 48) > pskclient1.txt

write a stunnel client configuration file *stunnel-client.conf*::

    output = stunnel-client.log
    client = yes
    
    [beremiz]
    accept = 3002
    connect = [PLC]:3001
    PSKidentity = client1
    PSKsecrets = pskclient1.txt

start stunnel client side::

    stunnel stunnel-client.conf

You could now connect beremiz with classic URI_location = PYRO://127.0.0.1:3002

--------------------
Server setup (PLC)
--------------------

import the client key in a keyfile psk.txt, concatening all client key.

write a stunnel server  configuration file *stunnel-server.conf*::

    output = stunnel-server.log
    
    [beremiz]
    accept = 3001
    connect = 127.0.0.1:3000
    PSKsecrets = psk.txt

start stunnel server side::

    stunnel stunnel-server.conf
    
more documentation on stunnel http://www.stunnel.org/docs.html

The WAMP connector
------------------

WAMP is an open standard WebSocket subprotocol that provides two application messaging 
patterns in one unified protocol: Remote Procedure Calls + Publish & Subscribe.

Beremiz WAMP connector implementation uses Autobahn and crossbar.

URI_location :
	* WAMP://127.0.0.1:8888#Automation#2534667845

more information about WAMP can be found on http://wamp.ws/