It is useful to run pypilot directly from the command line to quickly start and stop the server for debugging and development.
Only one server process (which listens on port 21331 for clients) can be run at a time. To ensure no other process is running execute:
$ ps aux | grep python
If another process already is bound to this port when you execute a server script, you will see the message: signalk_server: bind failed, try again.
Under openplotter, it might be useful to disable pypilot from the pypilot tab in openplotter config. If pypilot is installed as a systemd service:
$ sudo service pypilot stop
$ sudo sv d pypilot