Can the standard port number of Webclient be changed manually ?

The used standard portnumber of the WinCC OA webclient can be changed by editing  <Version_Dir>/scripts/webclient_http.ctl  in the following way (and saving it into the <Project_Dir>/scripts):

Grep for the following statement...

httpServer(false, 80, 443);

...and change it to your needs

httpServer(false, <your used port number>, 443);