Introduction
Terminal Services is the configurable service included in the Windows 2000 Server operating system that gives it the capability to run 32-bit Windows-based applications centrally from a server. This technology was introduced in Windows NT® Server, Terminal Server Edition, version 4.0, where it continues to deliver the base terminal emulation functionality that customers ask for today. In the Windows 2000 operating system, Terminal Services are fully integrated with the Windows 2000 Server kernel. Terminal Services emulator clients are available for many different desktop platforms (MS-DOS®, Windows, Macintosh, UNIX, and others.) Non-Windows-based desktops require third party add-on software.
Unlike the traditional client/server environment, when Terminal Services are enabled in Windows 2000 Server, all the application processing occurs on the server. The Terminal Services client performs no local processing of applications, it just displays the application output. The Terminal Services technology transmits only the application presentation—the graphical user interface (GUI)—to the client. Each user logs on and perceives his or her session only, which is transparently managed by the server operating system and is independent from any other client session.
From an application development perspective, one of the biggest benefits of Terminal Services is that well-behaved 16- or 32-bit Windows-based applications run, as is—no programming changes are required to run them under Terminal Services. However, this does not mean that all existing applications run equally well under Terminal Services. Understanding how to design applications that take advantage of the new capabilities of Windows 2000 Terminal Services is important. It’s also important to understand how bad programming habits are magnified in the Terminal Services environment, and to recognize where specific programming practices for the multiuser environment can be applied.
Following these guidelines does not limit or compromise the ability of an application to function in the traditional Windows-based client/server environment—Terminal Services-optimized applications work well in both environments.
Note: This white paper examines optimization techniques any application developer can use to ensure his or her Windows-based application runs well under Terminal Services. There is also support in the Windows 2000 Server operating system for a small set of Windows APIs available for Terminal Services. This white paper does not include information on those APIs. A separate white paper is available titled "Using and Understanding APIs for Terminal Server."
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