If you have SSH access to the machine, you should be able to use SSH port forwarding to accomplish this. I'm assuming you're using Windows (based on the C# tag), so you can use Putty as explained here: Using port forwarding with PuTTY. Just follow those instructions to forward the desired port on "localhost" to the server that serves the WSDL.
Alternatively, if you're on a *nix based machine or a Mac, use SSH w/ the following command:
ssh -L PORTYOUWILLUSE:localhost:PORTONSERVER username@serverhostname
For example, if the WSDL were served on port 80, you could do
ssh -L 80:localhost:80 username@server
Once you're logged in (with either method), any requests to localhost on port 80 will be rerouted to the server.