Use WinSock for transport
Use WinSock for transport checkbox enables or disables working via WinSock.
On some PCs, a program called WinSock Proxy (WSP) Client is installed. This client modifies the way Windows handles IP routing.
When working with such a PC with the VSP in default mode (with the Use WinSock for transport checkbox unchecked), the VSPD will not be able to connect to remote IP addresses (addresses beyond the scope of the current subnet), but will be able to connect to local addresses.
When something like this happens, you should mark this checkbox and thus instruct the VSPD to use WinSock for transport, rather than the default mechanism (called TDI, Transport Device Interface).