I am building a new application that receives data from a number of external devices and needs to make it available to a number of different components. ZeroMQ seems purpose-built for the "data bus" aspect of my architecture.
I recently became aware that zmq STREAM sockets can connect to native TCP sockets and send/received messages. Using zmq throughout has a lot of appeal, but I have one problem that I don't know how to get around.
One of my devices needs to be set up. That is, I connect a socket to it, send it some configuration information, then sit back and wait for it to send me data. The device also has a "reset" capability (useful in some contexts), that requires re-sending the configuration information. Doing this depends upon having visibility to the setup/tear-down stage of the socket interface. I need to know when a new connection is established, so I can send the necessary configuration messages.
It seems that zmq is purposely designed to shield me from that knowledge. Is there a way to do what I want? Or should I just use regular sockets for this interface?
Well, it turns out that reading (the right version of) the fine manual can be instructive.
When a connection is made, a zero-length message will be received by the application. Similarly, when the peer disconnects (or the connection is lost), a zero-length message will be received by the application.
I guess all that remains is to disambiguate between connect and disconnect. Still looking for advice from the community, if others have dealt with this situation before.