title: zeromq plain authentication -> example with C++ library?
body: <p>I cannot get the plain authentication to work with the core zeromq C++ library. I can get it to work with pyzmq with no issues. </p>
  
  <p>I noticed that the C and Python zeromq APIs have an authenticator that is run as a separate thread, but I don't see a similar component in the core C++ API. I am suspecting this is the problem, but I don't see where I can instantiate an authenticator in the C++ library. Has anyone been able to do this?</p>
  
  <p>Any ideas are welcome, thanks!</p>
  
  <p>--John</p>