QaaWS unable to talk to CMS (FWM 01005)

I set up a universe and created a QaaWS using the wizard.

When I try to access the WSDL by copying the provided link to my browser, i get the following message "Unable to open a socket to talk to CMS xyz (FWM 01005)"

I also tried to display all deployed webservices by accessing http://HOST:PORT/dswsbobje/qaawsservices, but again, the message is "Available QaaWS services. Unable to open a socket to talk to CMS xyz (FWM 01005)"

We use BOE XI 3.0 and the CMS is set to port 6420. I suspect we misconfigured something. Perhaps the webservice is trying to reach the CMS via standard port 6400.

Do you know how to fix this problem or if a log file is available to check the details of this error?

Thanks in advance!