"ss: command not found" when running start.sh on Mac

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.