Reliable and efficient networking library in c++ [on hold]

I have a need to send critical data from one system to other in my application in embedded systems in c++. I am trying to find out a reliable & efficient networking library in c++. We looked at ZeroMQ pub-sub but it doesn't seem to be reliable as pub-sub doesn't talk to each other.Its very difficult keep track of what is missing. we can't afford to loose any data. We can't use ZeroMQ REQ-REP pattern as well as that slows down the process a bit. We need to transfer huge data in very min time without loosing any data. If we loose some data (should be minimum possible) there should be some way for us to know the details about missing data. Using a pattern which uses a message broker is also not suiting our requirement (looked at MQTT).

Can anyone please let me know what other networking libraries for c++ available which is reliable and efficient.