- Install homebrew
 ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
- Intall iperf
 brew install iperf3
- Run server on machine 1:
 iperf3 -s
- Run speedtest on machine 2:
 iperf3 -c <machine 1>
- Both machine will show speed test results
Enjoy!
Ref:
- https://www.macobserver.com/tmo/answers/how-to-test-speed-home-network-iperf