What is Windows Sockets
The Windows Sockets specification defines a network programming interface for Microsoft Windows which is based on the "socket" paradigm popularized in the Berkeley Software Distribution (BSD) from the University of California at Berkeley. It encompasses both familiar Berkeley socket style routines and a set of Windows-specific extensions designed to allow the programmer to take advantage of the message-driven nature of Windows.
The Windows Sockets Specification is intended to provide a single API to which application developers can program and multiple network software vendors can conform. Furthermore, in the context of a particular version of Microsoft Windows, it defines a binary interface (ABI) such that an application written to the Windows Sockets API can work with a conformant protocol implementation from any network software vendor. This specification thus defines the library calls and associated semantics to which an application developer can program and which a network software vendor can implement.
Network software which conforms to this Windows Sockets specification will be considered "Windows Sockets Compliant". Suppliers of interfaces which are "Windows Sockets Compliant" shall be referred to as "Windows Sockets Suppliers". To be Windows Sockets Compliant, a vendor must implement 100% of this Windows Sockets specification.
Applications which are capable of operating with any "Windows Sockets Compliant" protocol implementation will be considered as having a "Windows Sockets Interface" and will be referred to as "Windows Sockets Applications".
This version of the Windows Sockets specification defines and documents the use of the API in conjunction with the Internet Protocol Suite (IPS, generally referred to as TCP/IP). Specifically, all Windows Sockets implementations support both stream (TCP) and datagram (UDP) sockets.
While the use of this API with alternative protocol stacks is not precluded (and is expected to be the subject of future revisions of the specification), such usage is beyond the scope of this version of the specification.
Berkeley Sockets
The Windows Sockets Specification has been built upon the Berkeley Sockets programming model which is the de facto standard for TCP/IP networking. It is intended to provide a high degree of familiarity for programmers who are used to programming with sockets in UNIX and other environments, and to simplify the task of porting existing sockets-based source code. The Windows Sockets API is consistent with release 4.3 of the Berkeley Software Distribution (4.3BSD).
Portions of the Windows Sockets specification are derived from material which is Copyright (c) 1982-1986 by the Regents of the University of California. All rights are reserved. The Berkeley Software License Agreement specifies the terms and conditions for redistribution.
Winsock API
Winsock is an API that allows Windows-based applications to access the transport protocols. Winsock in Windows 2000 is a protocol-independent networking API. Winsock is the Windows 2000 implementation of the widely-used Sockets API, the standard for accessing datagram and session services over TCP/IP, NWLink IPX/SPX NetBIOS, and AppleTalk. Applications written to the Winsock interface include File Transfer Protocol (FTP) and Simple Network Management Protocol (SNMP). Winsock performs the following:
- Provides a familiar networking API for programmers using Windows or UNIX.
- Offers binary compatibility between the heterogeneous, Windows-based TCP/IP stack and utility vendors.
- Supports both connection-oriented and connectionless protocols.
Windows 2000 includes Winsock 1.1 support. Winsock 2.0 extends the Winsock 1.1 interface to provide access to networks using protocols other than TCP/IP, such as NetWare and AppleTalk. Winsock 2.0 provides the following enhancements over Winsock 1.1:
- Name registration and resolution.Winsock 2.0 provides an interface that applications can use to access many different namespaces, such as Domain Name System (DNS), Novell Directory Services (NDS), and X.500.
- Support for real-time multimedia communications.Winsock supports several multimedia enhancements, including Quality of Service (QoS).
- Protocol-independent multipoint and multicast.Winsock 2.0 enables applications to take advantage of the multipoint and multicast capabilities of transport stacks.
Winsock Architecture
Winsock 2.0 is a Windows Open Systems Architecture (WOSA)–compliant interface that enables a front-end application and a back-end service to communicate. The Winsock 2.0 interface includes the following components:
- The Winsock 1.1 Application Programming Interface (API)
- The Winsock 2.0 Application Programming Interface (API)
- The Winsock 2.0 Transport Service Providers
- Layered Service Providers
Figure B.11 shows the Winsock 2.0 architecture.
