Could you update lwIP to version 2.2.1 ?

[GitPingPong]

A lot of bugs have been solved.

https://savannah.nongnu.org/projects/lwip/

https://git.savannah.nongnu.org/cgit/lwip.git/snapshot/lwip-STABLE-2_2_1_RELEASE.tar.gz

The main change preventing the current code compile is that the function udp_sendto does not accept src_ip and src_port. And udp_recv_fn also has 2 parameters less.

A few twist can be made to let the code compile, but during testing I found it not working. More investigation may be required.