computing Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, hardware and softw ...

, the Windows Sockets API (WSA), later shortened to Winsock, is an

application programming interface An application programming interface (API) is a connection between computers or between computer programs. It is a type of software Interface (computing), interface, offering a service to other pieces of software. A document or standard that des ...

(API) that defines how

Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

network

application software Application software is any computer program that is intended for end-user use not operating, administering or programming the computer. An application (app, application program, software application) is any program that can be categorized as ...

should access network services, especially

TCP/IP The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are ...

. It defines a standard interface between a Windows TCP/IP client application (such as an

FTP client The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network A computer network is a collection of communicating computers and other dev ...

or a

web browser A web browser, often shortened to browser, is an application for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's scr ...

) and the underlying TCP/IP

protocol stack The protocol stack or network stack is an implementation of a computer networking protocol suite or protocol family. Some of these terms are used interchangeably but strictly speaking, the ''suite'' is the definition of the communication protoc ...

. The nomenclature is based on the

Berkeley sockets A Berkeley ( BSD) socket is an application programming interface (API) for Internet domain sockets and Unix domain sockets, used for inter-process communication (IPC). It is commonly implemented as a library of linkable modules. It originated wi ...

API used in

BSD The Berkeley Software Distribution (BSD), also known as Berkeley Unix or BSD Unix, is a discontinued Unix operating system developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berkeley, beginni ...

for communications between programs.

Background

Early Microsoft operating systems, both MS-DOS and Microsoft Windows, offered limited networking capability, chiefly based on

NetBIOS NetBIOS () is an acronym for Network Basic Input/Output System. It provides services related to the session layer of the OSI model allowing applications on separate computers to communicate over a local area network. As strictly an API, Net ...

. In particular, Microsoft did not offer support for the TCP/IP protocol stack at that time. A number of university groups and commercial vendors, including the PC/IP group at

MIT The Massachusetts Institute of Technology (MIT) is a private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of modern technology and sc ...

FTP Software FTP Software, Inc., was an American software company incorporated in 1986 by James van Bokkelen, John Romkey (co-author of the MIT PC/IP package), Nancy Connor, Roxanne van Bokkelen (née Ritchie), Dave Bridgham, and several other founding shar ...

Sun Microsystems Sun Microsystems, Inc., often known as Sun for short, was an American technology company that existed from 1982 to 2010 which developed and sold computers, computer components, software, and information technology services. Sun contributed sig ...

Ungermann-Bass Ungermann-Bass, Inc., also known as UB and UB Networks, was a computer networking company in the 1980s to 1990s. Located in Santa Clara, California, UB was the first large networking company independent of any computer manufacturer. Along with co ...

, and Excelan, introduced TCP/IP products for MS-DOS, often as part of a hardware/software bundle. When Windows 2.0 was released, these vendors were joined by others such as Distinct and

NetManage NetManage Inc. was a software company based in Cupertino, California, founded in 1990 by Zvi Alon, an Israeli engineer. The company's development centre was located at the MATAM technology park, in Haifa, Israel. In June 2008 the company was ac ...

in offering TCP/IP for Windows. The drawback faced by all of these vendors was that each of them used their own API (Application Programming Interface). Without a single standard programming model, it was difficult to persuade independent software developers to create networking applications which would work with any vendor's underlying TCP/IP implementation. Add to this the fact that end users were wary of getting locked into a single vendor and it became clear that some standardization was needed. The Windows Sockets project had its origins in a Birds of a Feather session held at Interop '91 in San Jose on October 10, 1991. It is based on socket specifications created by NetManage and which it put into public domain at this meeting. At the time the NetManage socket was the only 100% DLL-based,

multi-threaded In computer architecture, multithreading is the ability of a central processing unit (CPU) (or a single core in a multi-core processor) to provide multiple threads of execution. Overview The multithreading paradigm has become more popular a ...

product for

Windows 3.0 Windows 3.0 is the third major release of Microsoft Windows, launched on May 22, 1990. It introduces a new graphical user interface (GUI) that represents applications as clickable icons, instead of the list of file names in its predecessors. ...

available. The first edition of the specification was authored by Martin Hall, Mark Towfiq of Microdyne (later

), Geoff Arnold of

, and Henry Sanders and

J Allard J Allard (born James Allard, on January 12, 1969 in Glens Falls, New York) is an American businessman. He is the chief executive officer of Project 529, a company that builds software for cyclists and law enforcement. Prior to starting Project 52 ...

Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...

, with assistance from many others. There was some discussion about how best to address the copyright, intellectual property, and potential anti-trust issues, and consideration was given to working through the

IETF The Internet Engineering Task Force (IETF) is a standards organization for the Internet standard, Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster ...

or establishing a non-profit foundation. In the end, it was decided that the specification would simply be copyrighted by the five authors as (unaffiliated) individuals. All the participating developers resisted the shortening of the name to simple Winsock for a long time, since there was much confusion among users between the API and the DLL library file (winsock.dll) which only exposed the common WSA interfaces to applications above it. Users would commonly believe that only making sure the DLL file was present on a system would provide full TCP/IP protocol support.

Technology

The Windows Sockets API specification defines two interfaces: the

API An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build ...

used by application developers, and the SPI, which provides a means for network software developers to add new protocol modules to the system. Each interface represents a contract. The API guarantees that a conforming application will function correctly with a conforming protocol implementation from any network software vendor. The SPI contract guarantees that a conforming protocol module may be added to Windows and will thereby be usable by an API-compliant application. Although these contracts were important when Windows Sockets was first released, since network environments required multi-protocol support (see above) they are now of only academic interest. Included in the Windows Sockets API version 2.0 are functions to use

IPX/SPX IPX/SPX stands for Internetwork Packet Exchange/Sequenced Packet Exchange. IPX and SPX are networking protocols used initially on networks using the (since discontinued) Novell NetWare operating systems. They also became widely used on networks ...

, although the protocol was all but obsolete already at the time WSA 2.0 shipped.

has shipped the

protocol stack with all recent versions of Windows, and there are no significant independent alternatives. Nor has there been significant interest in implementing protocols other than TCP/IP. Windows Sockets code and design are based on BSD sockets, but provides additional functionality to allow the API to comply with the regular Windows programming model. The Windows Sockets API covered almost all the features of the BSD sockets API, but there were some unavoidable obstacles which mostly arose out of fundamental differences between Windows and

Unix Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

(though Windows Sockets differed less from BSD sockets than the latter did from

STREAMS A stream is a continuous body of surface water flowing within the bed and banks of a channel. Depending on its location or certain characteristics, a stream may be referred to by a variety of local or regional names. Long, large stream ...

). All function calls in the API begin with the

moniker A nickname, in some circumstances also known as a sobriquet, or informally a "moniker", is an informal substitute for the proper name of a person, place, or thing, used to express affection, playfulness, contempt, or a particular character trait ...

, e.g. for sending data on a connected socket. However it was a design goal of Windows Sockets that it should be relatively easy for developers to port socket-based applications from

to Windows. It was not considered sufficient to create an API which was only useful for newly written Windows programs. For this reason, Windows Sockets included a number of elements which were designed to facilitate porting. For example,

applications were able to use the same variable to record both networking errors and errors detected within

standard C library The C standard library, sometimes referred to as libc, is the standard library for the C programming language, as specified in the ISO C standard.ISO/ IEC (2018). '' ISO/IEC 9899:2018(E): Programming Languages - C §7'' Starting from the origin ...

functions. Since this was not possible in Windows, Windows Sockets introduced a dedicated function, , to retrieve error information. Such mechanisms were helpful, but application porting remained extremely complex. Many original

applications had been implemented by using system features specific to

, such as

pseudo terminal In some operating systems, including Unix-like systems, a pseudoterminal, pseudotty, or PTY is a pair of pseudo-device endpoints (files) which establish an asynchronous, Duplex (telecommunications), bidirectional communication (IPC socket, IPC) c ...

s and the fork system call, and reproducing such functionality in Windows was problematic. Within a relatively short time, porting gave way to the development of dedicated Windows applications.

Specifications

* Version 1.0 (June 1992) defined the basic operation of Winsock. It was kept very close to the existing interface of Berkeley sockets to simplify porting of existing applications. A few Windows-specific extensions were added, mainly for asynchronous operations with message-based notifications. : Although the document didn't limit support to TCP/IP, TCP and UDP were the only protocols explicitly mentioned. Most vendors only delivered TCP/IP support, although Winsock from DEC included

DECNet DECnet is a suite of network protocols created by Digital Equipment Corporation. Originally released in 1975 in order to connect two PDP-11 minicomputers, it evolved into one of the first peer-to-peer network architectures, thus transforming DEC ...

support as well. * Version 1.1 (January 1993) made many minor corrections and clarifications of the specification. The most significant change was the inclusion of the function. * Winsock 2 was a

backwards-compatible In telecommunications and computing, backward compatibility (or backwards compatibility) is a property of an operating system, software, real-world product, or technology that allows for interoperability with an older legacy system, or with Input ...

extension of Winsock 1.1. It added support for protocol-independent name resolution, asynchronous operations with event-based notifications and completion routines, layered protocol implementations,

multicast In computer networking, multicast is a type of group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast differs from ph ...

ing, and

quality of service Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitat ...

. It also formalized support for multiple protocols, including

and

DECnet DECnet is a suite of network protocols created by Digital Equipment Corporation. Originally released in 1975 in order to connect two PDP-11 minicomputers, it evolved into one of the first peer-to-peer network architectures, thus transforming DEC ...

. The new specification allowed sockets to be optionally shared between processes, incoming connection requests to be conditionally accepted, and certain operations to be performed on socket groups rather than individual sockets. Although the new specification differed substantially from Winsock 1, it provided source- and binary-level compatibility with the Winsock 1.1 API. One of the lesser known additions was the Service Provider Interface (SPI) API and Layered Service Providers. * Versions 2.0.x (May 1994 onwards) had internal draft status, and were not announced as public standards. * Version 2.1.0 (January 1996) was the first public release of the Winsock 2 specification. * Version 2.2.0 (May 1996) included many minor corrections, clarifications, and usage recommendations. It was also the first version to remove support for 16-bit Windows applications. * Version 2.2.1 (May 1997) and Version 2.2.2 (August 1997) introduced minor functionality enhancements. Mechanisms were added for querying and receiving notification of changes in network and system configuration. * The

IPv6 Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communication protocol, communications protocol that provides an identification and location system for computers on networks and routes traffic ...

Technical Preview for

Windows 2000 Windows 2000 is a major release of the Windows NT operating system developed by Microsoft, targeting the server and business markets. It is the direct successor to Windows NT 4.0, and was Software release life cycle#Release to manufacturing (RT ...

(December 2000) saw the first implementation of RFC 2553 (March 1999, later obsoleted by RFC 3493), a protocol-independent API for name resolution, which would become part of Winsock in

Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct successor to Windows 2000 for high-end and business users a ...

Updates in Windows 8

Windows 8 Windows 8 is a major release of the Windows NT operating system developed by Microsoft. It was Software release life cycle#Release to manufacturing (RTM), released to manufacturing on August 1, 2012, made available for download via Microsoft ...

includes the "RIO" (Registered IO) extensions for Winsock. These extensions are designed to reduce the overhead of the user to kernel mode transition for the network data path and the notification path, but use the rest of the regular Windows TCP and UDP stack (and uses existing network cards). The setup path (for example, the "connect" function) is unchanged from the regular Winsock path.

Implementations

Microsoft implementations

* Microsoft did not supply an implementation of Winsock 1.0. * Version 1.1 of Winsock was supplied in an add-on package (called Wolverine) for Windows for Workgroups (code named Snowball). It was an integral component of Windows 95 and

Windows NT Windows NT is a Proprietary software, proprietary Graphical user interface, graphical operating system produced by Microsoft as part of its Windows product line, the first version of which, Windows NT 3.1, was released on July 27, 1993. Original ...

from versions 3.5 and onwards (the initial commercially available version of Windows NT, version 3.1, included only a proprietary and quite incomplete implementation of TCP/IP based on the AT&T UNIX System V "STREAMS" API ). * Version 2.1 of Winsock was supplied in an add-on package for Windows 95. It was an integral component of

Windows 98 Windows 98 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. It was the second operating system in the 9x line, as the successor to Windows 95. It was Software ...

, Windows NT 4.0, and all subsequent Windows releases. (Microsoft did not supply implementations of Winsock 2 for Windows 3.x or Windows NT 3.x.) * Recent versions of Winsock 2.x have been delivered with new Windows releases or as part of service packs. * Winsock 2 is extensible by a mechanism known as a Layered Service Provider (LSP). Winsock LSPs are available for a wide range of useful purposes, including Internet parental controls, web content filtering, QoS etc. The layering order of all providers is kept in the Winsock Catalog. In previous versions of Windows, removing a buggy LSP could result in corruption of the Winsock catalog in the registry, potentially resulting in a loss of ''all network connectivity''. Winsock in Windows XP Service Pack 2, Windows Server 2003 Service Pack 1 and all later Windows operating systems has the ability to self-heal after a user uninstalls such an LSP.

Other implementations

*Among the other vendors offering Winsock-compliant TCP/IP and UDP/IP stacks were (alphabetically)

3Com 3Com Corporation was an American digital electronics manufacturer best known for its computer network products. The company was co-founded in 1979 by Robert Metcalfe, Howard Charney and others. Bill Krause joined as President in 1981. Metcalfe ex ...

, Beame & Whiteside, DEC, Distinct, Frontier,

IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...

, Microdyne,

Novell Novell, Inc. () was an American software and services company headquartered in Provo, Utah, that existed from 1980 until 2014. Its most significant product was the multi-platform network operating system known as NetWare. Novell technolog ...

and Trumpet Software International. *

Trumpet Winsock Trumpet Winsock is a Internet protocol suite, TCP/IP stack for Windows 3.x that implemented the Winsock, Winsock API, which is an API for Network socket, network sockets. It was developed by Peter Tattam from Trumpet Software International and Sof ...

by Peter Tattam was one of the few Winsock 1.0 implementations that could be installed under

, which had no built-in support for Winsock. Trumpet was also the most popular

shareware Shareware is a type of proprietary software that is initially shared by the owner for trial use at little or no cost. Often the software has limited functionality or incomplete documentation until the user sends payment to the software developer. ...

implementation of Winsock for Windows 3.x. Trumpet Winsock 5.0 is available for

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft and the first of its Windows 9x family of operating systems, released to manufacturing on July 14, 1995, and generally to retail on August 24, 1995. Windows 95 merged ...

/ 98 and

and includes a Winsock 1.1 compliant IPv6 stack for these operating systems. *The Wine project contains a source and binary compatible reimplementation of Winsock on top of the BSD sockets API.

References

External links

MSDN - Windows Socket 2 What's New Reference

MSDN - Windows Socket 2 Start page

Sockets FAQ
- Windows Sockets FAQ * - Winsock C++ Programming
Porting Berkeley Socket programs to Winsock

Windows Network Development blog
— Microsoft developer blog covering Winsock, WSK, WinINet, Http.sys, WinHttp, QoS and System.Net, with a focus on features being introduced in

Windows Vista Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, released five years earlier, which was then the longest time span between successive releases of Microsoft W ...

Brief History of Microsoft on the Web

WinSock Development Information

Winsock Programmer's FAQ
{{Authority control Network socket History of the Internet 1992 software Windows communication and services Microsoft application programming interfaces