Sockets and Networking

Windows Sockets 2 uses the sockets paradigm that was first popularized by Berkeley Software Distribution (BSD) UNIX. It was later adapted for Microsoft Windows in Windows Sockets 1.1.

One of the primary goals of Winsock has been to provide a protocol-independent interface fully capable of supporting emerging networking capabilities, such as real-time multimedia communications.

Winsock is an interface, not a protocol. As an interface, it is used to discover and utilize the communications capabilities of any number of underlying transport protocols. Because it is not a protocol, it does not in any way affect the bits on the wire, and does not need to be used on both ends of a communications link.

Windows Sockets programming previously centered on TCP/IP. Some of the programming practices that worked with TCP/IP do not work with every protocol. As a result, the Winsock API added new functions where necessary to handle several protocols.

Winsock has changed its architecture to provide easier access to multiple transport protocols. Following the Windows Open System Architecture (WOSA) model, Winsock now defines a standard service provider interface (SPI) between the application programming interface (API), with its functions exported from Ws2_32.dll and the protocol stacks. Consequently, Winsock support is not limited to TCP/IP protocol stacks as is the case for Windows Sockets 1.1. For more information,see the discussion of Windows Sockets 2 Architecture in Microsoft Visual Studio.

There are new challenges in developing Windows Sockets 2 applications. When sockets only supported TCP/IP, a developer could create an application that supported only two socket types: connectionless and connection-oriented. Connectionless protocols used SOCK_DGRAM sockets, and connection-oriented protocols used SOCK_STREAM sockets. These are just two of the many new socket types. Additionally, developers can no longer rely on socket type to describe all the essential attributes of a transport protocol.

Sockets are not part of the Win32 library. You ll need to consult the platform SDK for detailed information about the WinSock APIs. The online Help for the Platform SDK contains complete samples that demonstrate how to implement socket-based client and server applications. For an in-depth comparison between UNIX sockets and WinSock, see the discussion of Socket Programming Considerations in the Microsoft Platform SDK.