WCF by default adds the listen address of the endpoints in the WSDL so in a scenario where the private address of the server is different from the public address you get incorrect endpoint address in WSDL.
Now this behavior might not work in certain scenarios and you want the metadata generation to dynamically pick the address from the request headers, similar to ASMX web services.
UseRequestHeadersForMetadataAddressBehavior enables exactly this. This opt-in behavior sets the address of endpoints dynamically, based on the request header.
Like all other WCF behaviors, this behavior can be enabled either in the code or config.
As part of this behavior, you can also specify default ports for different schemes (http,https etc..). These default ports come into action in following scenarios:
When metadata is accessed over http, all http based URIs are substitued with the Hostname and host port from the Host header
All https based URIs picks the default port registered against https scheme
Similarly when metadata is accessed over https, all https URIs pick up the host and port from the host header and http based URIs used the default port registered against http scheme
This behavior is added in .NET 4.0 and there is a QFE available for 3.5 SP1: http://support.microsoft.com/kb/971842