Changing Port Number

[avatar-lavventura]

I am having following error:

[Browsersync] Access URLs:
 ---------------------------------------
       Local: http://localhost:3002
    External: http://<IP>:3002
 ---------------------------------------
          UI: http://localhost:3003
 UI External: http://<IP>:3003
 ---------------------------------------
[Browsersync] Serving files from: ./app
[Browsersync] Watching files...
events.js:165
      throw er; // Unhandled 'error' event

[Q] On which file could I change the port number?