Cannot request a custom bind port '-R <PORT>:'. You may
either specify a reserved TCP address with '-R address:port:' or you may let
the server choose a random remote port for you with '-R 0:'. Example: ssh -R
0:localhost:22 ... Example: ssh -R 1.tcp.eu.ngrok.io:21412:localhost:22 ...
If you're having trouble resolving this error, please reach out to support@ngrok.com.