(Quick Reference)

run-gwt-client

Run the GWT Development Mode client.

This hosts your GWT code and executes it as Java. You will need the GWT plugin installed in your browser of choice.

Then visit http://localhost:8080/<yourpage>?gwt.codesvr=127.0.0.1:9997

See https://developers.google.com/web-toolkit/doc/latest/DevGuideCompilingAndDebugging