The u command sets a Portal URL to the cube. The cube will communicate with this URL
Send u:http://www.max-portal.elv.de:80 to set the Cubes portal URL to http://www.max-portal.elv.de, Port: 80 The cube will communicate with the ELV portal server
Send u:http://max.eq-3.de:80 to set the Cubes portal URL to http://max.eq-3.de, Port: 80 The cube will communicate with the eq-3 portal server