The 'ZMQ_RCVMORE' option shall return a boolean value indicating if the multi-part
message currently being read from the specified 'socket' has more message parts to
follow.
The 'ZMQ_MCAST_LOOP' option shall control whether data sent via multicast transports
using the specified 'socket' can also be received by the sending host via loopback.
The 'ZMQ_RATE' option shall set the maximum send or receive data rate for multicast
transports such as in the man page of zmq_pgm[7] using the specified 'socket'.