configure mavproxy with serial and udp

Dear all,

i want to connect ardupilot in serial on one side, and mission planner as UDP on other side.
i was able to open the serial port and getting heart beat and data from the serial on mavproxy.
but when i try to connect udpin (tried also udpout) i see that there packets that sent.
but when i try to connect Mission Planner (the FC is with APM) i getting timeout, and don't able to connect.
i tried on windows and osx (intel chip) with no success.

how can i make it work?

No files, tests, or commands are identified. Start by reviewing MAVProxy's serial and UDP connection entry points and the Mission Planner connection settings, using the reported serial heartbeat and UDP timeout as reproduction criteria; the issue is done when Mission Planner connects successfully on the stated Windows and macOS setups.

Written by the indexing model from the issue text.