Chapter 10. Windows Terminal Services

In the old days of mainframe computing, employees typically used terminal equipment to connect to a big machine in a white room that ran all their programs and calculations. The terminal showed only the user interface and processed keystrokes and responses from the user; the mainframe in the back actually executed the programs and displayed the results to the end user, so very little processor intelligence was at the client equipment end. This is largely why these terminal systems were called "dumb."

Although the move into the personal computing and desktop computing era made large inroads into corporate America, there are still some uses for dumb terminal (or in more modern terminology, "thin client") functionality. Windows Terminal Services (WTS) is a set of programs and utilities that enable this functionality on a more intelligent, contemporary level. In fact, you might already be familiar with Terminal Services in a scaled-down mode. Both Windows XP's Remote Assistance and Remote Desktop Connection utilities are examples of Terminal Services in action. Terminal Services passes only the user interface of a program running on a server to the client computer, which then passes back the appropriate keyboard strokes and mouse clicks. The server running Terminal Services, which many clients can access simultaneously, manages the connections and the active programs seamlessly, so it appears to the user that he's using his own computer rather than one servicing other active applications at the same time.

Why is this useful? Many corporations, in an effort to reduce desktop support responsibilities for their help desks as well as equipment acquisition costs, are deploying thin client computers with limited client-side functionality. These thin clients provide users with a window into a server that is running the applications they need. Microsoft Office, many accounting applications, and multitudes of other programs work effectively under a Terminal Services environment, and the reduced management headaches are worth the extra initial setup effort for some businesses. Think about the reduced cost of applying patches, upgrading software, or removing outdated programs. You apply, upgrade, or remove once, and bingo: your entire enterprise IT environment is updated. It's hard to argue with that. This mode of using Terminal Services is known as application mode.

Terminal Services has another common use: remote administration. This is a licensing, hassle-free way that you can connect to machines running a Terminal Services-compatible operating system, and can use the machine's interface almost exactly as if you were sitting in front of it. Windows 2000, XP, and Server 2003 come bundled with a license to do this. This is such a boon for administrators: you don't have to leave your cubicle to administer elements of Windows on servers in your machine room.

A Terminal Services connection uses port 3389 to establish a TCP/IP link to enable clients to log on to a session from their workstation. However, the Terminal Services Configuration applet and the Terminal Services Manager console, both of which I'll also cover in this chapter, enable you to change this port and a number of other properties about each connection.

Terminal Server has its own method for licensing clients that log on to terminal servers, separate from the licensing method for clients running one of the other flavors of Windows 2003. In addition to being enabled to use Terminal Services in their user account properties, clients must receive a valid license issued by a license server before they are allowed to log on to a terminal server. Later in this chapter I'll discuss in greater detail the subject of licensing issues when using Terminal Services.

Terminal Services support is not included in Windows Server 2003 Web Edition, although you can use the Remote Desktop Connection applet in the Control Panel to remotely administer the server. The Remote Desktop Connection applet cannot host applications for multiple users.