Send a request to a service in a remote server

I use the ff string to send a request call to a local server and it works fine:

service.DownloadStringAsyn(New Uri("http://localhost:12345/serviceName/"Service.svc/className/" & argument1 & "/" & argument2 ))

How do I modify this string when I want to access a remote server? Please give some reading material on this topic, if possible. Thanks for helping