Client-server communication in Vault is done via HTTP connections. This means that Vault can be set up with various HTTP features. Some of those features may keep your client from connecting, so let's go over how to handle things when the server is on SSL or a non-standard port.
Connecting on a different port
You can change your IIS settings to use a different port than 80. At the API level, you handle this when you set the URL on your web service object. For example, if you are using port 2112, you would set your DocumentService.URL value to http://servername:2112/AutodeskDM/Services/DocumentService.asmx
For login dialogs, Autodesk clients use the convention of adding the port to the end of the server name. For example, "servername:2112".
Connecting via SSL
If you have your server configured for SSL, you still handle things with the URL property. In this case your, DocumentService.URL would have the value of https://servername/AutodeskDM/Services/DocumentService.asmx
For login dialogs, the Autodesk convention is to have "https://" before the server name. For example, "https://servername".
Connecting via SSL on a different port
The default SSL port is 443. If you are using SSL on a different port, you can just combine the rules from above. For example: https://servername:2112/AutodeskDM/Services/DocumentService.asmx
The VaultFileBrowser sample in the SDK handles these cases. So feel free to borrow that code. The login dialog assumes the same server name syntax as the rest of the Autodesk clients.