I think the situation is more subtle than the poster admits.
No, ZeroMQ and successors do not tell you about socket state. You can't detect disconnection or reconnection. But then if a TCP connection fails in some way that does not lead to disconnection (packets getting dropped, remote machine powers down), it can't possibly tell you about that either, but you still need to deal with it. So in any case, you need some sort of application-level error detection and recovery; you need heartbeats, and serial numbers in messages, and a protocol for explicitly restarting a connection and performing the initial handshake. And once you have that, explicit connection events from ZeroMQ are much less important.
Admittedly, given that this is a TCP transport, reporting reconnections would still be useful, because TCP won't ever drop messages from the interior of a sequence itself (if it delivers 15, it has delivered 1 - 14 already), so you shouldn't need the serial numbers.
No, ZeroMQ and successors do not tell you about socket state. You can't detect disconnection or reconnection. But then if a TCP connection fails in some way that does not lead to disconnection (packets getting dropped, remote machine powers down), it can't possibly tell you about that either, but you still need to deal with it. So in any case, you need some sort of application-level error detection and recovery; you need heartbeats, and serial numbers in messages, and a protocol for explicitly restarting a connection and performing the initial handshake. And once you have that, explicit connection events from ZeroMQ are much less important.
Admittedly, given that this is a TCP transport, reporting reconnections would still be useful, because TCP won't ever drop messages from the interior of a sequence itself (if it delivers 15, it has delivered 1 - 14 already), so you shouldn't need the serial numbers.
And if it's really not possible to detect authentication failures, than that seems rubbish. And it seems that is indeed the case: https://github.com/zeromq/libzmq/issues/3505