OpenStack ZeroMQ (ZMQ) receiver listening port 9501

zmq-receiver receives messages on tcp://*:9501 with socket type PULL and
based on topic-name (which is extracted from received data), it forwards
data to respective local services, over IPC protocol.

matchmaker_ringfile   /etc/nova/matchmaker_ring.json   Matchmaker ring file (JSON)
rpc_zmq_bind_address  '*'                              ZeroMQ bind address
rpc_zmq_matchmaker    ceilometer.openstack.common.rpc. MatchMaker drivers
                      matchmaker.MatchMakerLocalhost
rpc_zmq_port          9501                             ZeroMQ receiver listening port
rpc_zmq_port_pub      9502                             ZeroMQ fanout publisher port
rpc_zmq_contexts      1                                Number of ZeroMQ contexts
rpc_zmq_ipc_dir       /var/run/openstack               Directory for holding IPC sockets