Fixed error caused by unnecessary reopening of listening socket.
Extracted packet retransmit logic to separate function.
Added robust implementation for sending data
Closes https://github.com/espressif/esp-idf/pull/3597
inet_aton returns 0 on failure, but socket_add_ipv4_multicast_group has to return negative values for failures
getaddrinfo sets res to zero of address could not resolved, but doesn't necessarily return an
error. res is now checked for zero before dereferencing
Merges https://github.com/espressif/esp-idf/pull/2814
