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4/8/2010

Following the Windows Open System Architecture (WOSA) model, Winsock defines a standard service provider interface (SPI) between the Winsock application programming interface (API) and the protocol stacks. Windows Sockets 2.2 support is not limited to TCP/IP protocol stacks as is the case for Windows Sockets 1.1.

The following table shows the built-in service providers that Windows Mobile operating systems (OS) provide:

Service provider	Description
WSPM	This is the default base TCP and UDP transport service provider. WSPM does not support all possible functionality, including multipoint and connect-time data transfer. WSPM is located in wspm.dll.
NSPM	This is the default Domain Name Service (DNS) namespace provider. NSPM is located in nspm.dll.

Together, these two providers offer most of the functionality available through Winsock 1.1, as well as some of the functionality of Winsock 2.2, such as scatter/gather and overlapped I/O.

Windows Mobile also provides a third service provider, located in ssllsp.dll, that is built in if SSL is included in your OS design. You can also create your own service providers. Preferably, you should document service providers that you create so that other application developers can make use of the extended abilities.