How can I serve Ionic app on a different port?

When running 2 ionic apps at the same time, it's not enough to specify a new port for the second app, you also need to specify a new port for live reload and dev logger or they will conflict with the first app:

ionic serve -p 8101 -r 8102 --dev-logger-port 8103 

Otherwise, you'll get connection error. Make sure firewall allows all those ports you use.

Try ionic platform add browser before,

or

ionic serve -p 8002 --dev-logger-port 8103

instead...