libczmq4 4.2.0-2 (arm64 binary) in ubuntu hirsute

 czmq (previously known as libzapi) provides a high-level C binding for
 0MQ, a lightweight messaging library.
 .
 This library provides higher level abstractions on top of the base
 library, with features such as:
  * Work with messages as strings, individual frames, or multipart messages.
  * Automatic closure of any open sockets at context termination.
  * Automatic LINGER configuration of all sockets for context termination.
  * Portable API for creating child threads and ØMQ pipes to talk to them.
  * Simple reactor with one-off and repeated timers, and socket readers.
  * System clock functions for sleeping and calculating timers.
  * Easy API to get/set all socket options.
  * Includes generic hash and list containers.