Default web ports can be changed in gravwell.conf with the Web-Port and Disable-HTTP-Redirector directives.
If you're co-locating Gravwell with a web server, you may find the default listeners on ports 80 and 443 conflict with your web server. You can set the HTTPS listening port with the "Web-Port" parameter in gravwell.conf, e.g. "Web-Port=4443". You can also disable redirection from port 80 to the Web-Port by setting "Disable-HTTP-Redirector=true" in gravwell.conf. See https://dev.gravwell.io/docs/#!configuration/parameters.md for more information.