Avalanche 4.x & 5.x
You need to change the default port 8009 that Apache Tomcat uses
The default port can be changed by modifying the server.xml file.
Be sure to stop/restart the Apache Tomcat Services after changing the XML.
The server.xml is located: Program Files\Wavelink\AvalancheMC\WebUtilities\Tomcat\conf
Be careful if changing any other port values in the server.xml as it could cause issues.