I take it you are running Tomcat behind an HTTP-server.
You have at least the following options to this.
1. Allow connections through a specific port to Tomcat. In Tomcat that port has to be defined as an HTTP connector. You then connect the Ebase designer using the defined port that you have exposed to the internet.
2. Set-up a tunnel to the server and then use the tunnel to talk directly to Tomcat on Tomcats HTTP port (normally 3030).
3. If you have your domain redirecting to HTTPS and that is what is causing the problem, you could set up a sub-domain that does not redirect to HTTPS.
http://www.mydomain.com redirects to
https://www.mydomain.com and
http://noredirect.mydomain.com stays on
http://noredirect.mydomain.com for example.