IP Packet Mirror : ippm
This "ippm" command tool is mirroring tcp or udp packets to another udp receiver (like MavlinkAnalizer). The mirroring packets are filtered by source-address, source-port, destination-address, or destination-port. To execute this command is required the supervisor permission.

The binary for osx is here.
When using on the other os, you can bulid the binary from c++ source code which is published GitHub. MIT licence. The "libcap.lib" is required for build.

Sample usage for MavlinkAnalyzer
MavlinkAnalyzer which decodes and displays mavlink message works at UDP server. The "ippm" is useful for mavlink capture between a drone and grand control with MavlinkAnalyzer.