We're working on the documentation, but don't let that stop you from joining in and helping us improve it! As for detecting that messages aren't being delivere

We're working on the documentation, but don't let that stop you from joining in and helping us improve it! As for detecting that messages aren't being delivered to a particular peer, at the moment that is not possible since zmq_send() is asynchronous from the point of view of the caller, i.e. the actual sending gets offloaded to a background thread. Unfortunately there's no straightforward way to map asynchronous error handling onto the socket API. I guess we could experiment with hitting the calling thread with a SIGPIPE or similar but signal handling on a lot of systems is suboptimal (to put it politely) and we also need to support Win32. So this whole area requires more thought...