I’m using ZeroMQ both in CxxProf and at work extensively. Just recently I came across a bug which was only reproducible in a quite complex network scenario. The network implementation used ZeroMQ Publish/Subscribe sockets, so I wrote a component which recorded the network transfer and allowed me to replay it afterwards. By doing this I could completely ditch all the network components involved in the original bug and replay what was causing the bug on my desktop PC.
The target group of ZmqRecorder is probably not the biggest, but I guess that someone could put it to good use. It’s possible to improve the Player-implementation and allow to replay with more control like pausing or playing backwards, but it’s good for my usecase now.