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/