Cannot send mavlink messages on MacOS

[sreejithkrishnanr]

Hi,
I am unable to send mavlink messages to AirSim in PX4 Drone simulation mode.

This is happening because in MacOS, the message sender address in not populated by read(int fildes, void *buf, size_t nbyte) function used to read data from socket.

https://github.com/Microsoft/AirSim/blob/5223c26f86d93b7a3b5961dab170a829a9d5baab/MavLinkCom/src/serial_com/UdpClientPort.cpp#L185-L190

Since the message sender address is not populated, the received message is ignored.
https://github.com/Microsoft/AirSim/blob/5223c26f86d93b7a3b5961dab170a829a9d5baab/MavLinkCom/src/serial_com/UdpClientPort.cpp#L234-L238

Using the recvfrom function like for other platforms fixes the problem in MacOS high sierra. I am not sure whether this will break something in other versions of MacOS.

[msb336]

Hi @sreejithkrishnanr
Thanks for your work on this! At this time, the airsim doesn't support osx builds, so all work towards compatibility is community driven. Please submit a pull request with the changes you have made and we'll review it as soon as we can!