ZMQ REQ-RESP, pattern, messages gets lost at the server side.

[rc1997258]

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Issue description

Currently, the proprietary software based on netconf protocol, uses ZMQ library to send and receive commands(API callbacks) over the tcp socket connections. Here, ZMQ REQ-RESP pattern is used.

Normally everything works fine, but when there is a new netconf session is being established on ZMQ server side, and the session gets stuck at the TLS handshake step, then some of the ZMQ commands are being sent successfully, but not received at the server side, and hence there is no response received at the client side.
This happens only when there is a TLS handshake stuck, but the IP used and port used for ZMQ communication is different, than the IP over which netconf session is being taken place, on the ZMQ server.

Could anyone please help me here. how to solve this problem?

Thanks in advance!

Environment

• libzmq version (commit hash if unreleased): 4.2.1 C++ ZMQ library
• OS:
  Centos 8

Minimal test code / Steps to reproduce the issue

What's the actual result? (include assertion message & call stack if applicable)

What's the expected result?

[kcexn]

Completely new to ZeroMQ, but is this related to the library? If the TLS handshake is stuck how do messages get passed from client to server? The messages will just get queued up at the client right?