You should create a web service provider alias (IS Admin Console > Settings > Web Services) and then configure your WSD to use this alias.
You do this by opening the WSD in Designer, clicking on the Binders tab, selecting your binder, and then choosing your alias from the Port alias drop-down in the Properties view (Note: if you had your WSD open already before creating the alias, you have to refresh it before the alias shows up in the drop-down).
Once you do this, the WSDL will contain the host name and port from the alias. The advantage of doing this is that, as you promote the web service from environment to environment, the WSDL will always pick up the value from the alias configured in that environment. It’s a beautiful thing.