I am not sure if this question belongs here as it may be a little to broad. If so, I apologize. Anyway, I am planning to start a project in python and I am trying to figure out how best to implement it, or if it is even possible in any practical way. The system will consist of several "nodes" that are essentially python scripts that translate other protocols for talking to different kinds of hardware related to i/o, relays to control stuff, inputs to measure things, rfid-readers etc, to a common protocol for my system. I am no programming or network expert, but this part I can handle, I have a module from an old alarm system that uses rs-485 that I can sucessfully control and read. I want to get the nodes talking to eachother over the network so I can distribute them to different locations (on the same subnet for now). The obvious way would be to use a server that they all connect to so they can be polled and get orders to flip outputs or do something else. This should not be too hard using twisted or something like it. 
The problem with this is that if this server for some reason stops working, everything else does too. I guess what I would like is some kind of serverless communication, that has no single point of failure besides the network itself. Message brokers all seem to require some kind of server, and I can not really find anything else that seems suitable for this. All nodes must know the status of all other nodes as I will need to be able to make functions based on the status of things connected to other nodes, such as, do not open this door if that door is already open. Maybe this could be done by multicast or broadcast, but that seems a bit insecure and just not right. One way I thought of could be to somehow appoint one of the nodes to accept connections from the other nodes and act as a message router and arrange for some kind of backup so that if this node crashes or goes away, another predetermined node takes over and the other nodes connect to it instead. This seems complicated and I am not sure this is any better than just using a message broker.
As I said, I am not sure this is an appropriate question here but if anyone could give me a hint to how this could be done or if there is something that does something similar to this that I can study. If I am beeing stupid, please let me know that too :)
There are messaging systems that don't require a central message broker. You might start by looking at ZeroMQ.
Serverless communication between network nodes in python