ZeroMQ

ROUTER Error Handling

ROUTER sockets do have a somewhat brutal way of dealing with messages they can’t send anywhere: they drop them silently. It’s an attitude that makes sense in working code, but it makes debugging hard. The “send identity as first frame” approach is tricky enough that we often get this wrong when we’re learning, and the ROUTER’s stony silence when we mess up isn’t very constructive.

Since ØMQ v3.2, there’s a socket option you can set to catch this error: ZMQ_ROUTER_MANDATORY. Set that on the ROUTER socket, and when you provide an unroutable identity on a send call, the socket will signal an EHOSTUNREACH error.