zmq_ctx_term() blocks while sockets closed
Observations:
I had the same problem. Despite the fact that I was closing the socket of ZMQ_REQ type, and zmq_close() returned 0, zmq_ctx_term() would still block. This was happening only after sending a message to a peer that was not running.
zmq_send() would return immediately, but zmq_recvmsg() would time out.
After that I was closing the socket and calling zmq_ctx_term(). Apparently, despite the fact that zmq_close() returned 0, the sent message was still in an outgoing queue, and for that reason zmq_ctx_term() would block.
Solution:
I solved the problem by setting ZMQ_LINGER option to half the value of ZMQ_RCVTIMEO. This behavior is actually described herehttp://api.zeromq.org/4-0:zmq-ctx-term