Toward a common API - Windows Sockets Applications Programming Interface standard - Forum

A standard is emerging that allows applications written for Microsoft Windows to run across many more TCP/IP options than was previously possible. The Windows Sockets Applications Programming Interface (API) grew out of the need for a common API between the two.

Widespread use of client/server applications calls for an extensive set of connectivity options. Because the Transmission Control Protocol/Internet Protocol (TCP/IP) is such a prevalent network protocol on multiple platforms, client/server applications must support it.

However, since more than 20 MS-DOS-based TCP/IP vendors currently exist, offering a variety of applications over many TCP/IP options means a lot of work for developers.

Not only do customers need support for their favorite TCP/IP, but developers must be able to update that support easily in new versions of the application with minimal code changes to their own applications. Validating each new TCP/IP or version thereof adds up to significant development costs and support.

As developers and vendors came up against the difficulties caused by the lack of standardization, they realized the need for a standard. Likewise, we at JSB Corp., in Scotts Valley, Calif., became familiar with the difficulties when we developed our own range of products. We developed a technical solution to meet our needs and decided to propose it as an industry standard.

At the Interop '91 trade show, a "Birds of a Feather" session chaired by JSB brought together the leading TCP/IP vendors and Windows applications developers, including Microsoft Corp., Redmond, Wash.; Sun Microsystems, Inc., Mountain View, Calif.; and FTP Software, Inc., North Andover, Mass.

WITHIN LIKE PARAMETERS

Vendors and developers alike agreed on the need for a standard API. By defining a standard, application developers and TCP/IP vendors could work within the same parameters, allowing products to function together.

A subcommittee then set out to develop a standard, the Windows Sockets API, which was first published in June 1992. Aimed at developers working in a Microsoft Windows environment, the Windows Sockets API defines an interface between a Windows application and a TCP/IP implementation.

Using this definition, an application operating under Windows and Windows NT over different vendors' TCP/IP stacks can run unchanged. The Windows Sockets API includes many Windows-specific extensions. These extensions let developers integrate the networking portions of applications into the message-driven Windows programming model.

The Windows Sockets API emerged from the Virtual Socket Library (VSL). This piece was developed at JSB as a linking interface to reduce its development workload. It provided individual code modules to connect the virtual interface to the actual interface used by each TCP/IP.

The Windows Sockets API is based on the Berkeley Sockets paradigm, recognized as the de facto standard for network programming under Unix and other environments.

Application developers currently face an important challenge: how to retain compatibility with existing TCP/IP stacks while moving toward products that comply with the emerging Windows Sockets API. Although the consortium seems to have agreed on the standard relatively quickly, the real test will be how rapidly developers adopt it.

There are some promising indicators, however. Windows Sockets API was very much in evidence at last month's Interop Fall '93, with a number of companies writing applications compatible with the interface.

Typical applications being written include distributed catalogued information systems; the Distributed Computing Environment of the Open Software Foundation, Cambridge, Mass.; terminal emulators; X servers; client/server database implementations; and file management systems.

Now standing at more than 300 members, the Windows Sockets Committee in January published Version 1.1 of the specification, proof that cooperation and not just competition can move the industry forward.

Among the companies announcing Windows Sockets implementations are 3Com Corp., Santa Clara, Calif; Distinct Corp., Saratoga, Calif.; Frontier Technologies Corp., Mequon, Wis.; FTP Software; JSB; IBM; Lan Design, Inc., Colorado Springs, Colo.; Microdyne Corp., Alexandria, Va.; Microsoft; Net-Manage, Inc., Cupertino, Calif.; Network Research Corp., Camarillo, Calif.; Novell, Inc., Provo, Utah; Sun Microsystems; Ungermann-Bass, Inc., Santa Clara, Calif.; Walker Richer & Quinn, Inc., Seattle; and The Wollongong Group, Inc., Palo Alto, Calif.

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