I was working through this repo's example on a Mac. When I got to this step...

Use the start script for starting a ledger & the java application:

...I tried running ./start.sh examples.pingpong.grpc.PingPongGrpcMain and received these error messages...

Starting sandbox
./start.sh: line 5: ss: command not found

Googling suggests that ss is a Linux tool that is not ported to Mac OS.

I'm happy to help resolve this if someone can recommend the proper resolution.