Generally in information technology, a terminal server is a hardware device or server that provides terminals (PCs, printers, and other devices) with a common connection point to a local or wide area network. The terminals connect to the terminal server from their RS-232C or RS-423 serial port. The other side of the terminal server connects through network interface cards (NIC) to a local area network (LAN) (usually an Ethernet or Token Ring LAN) through modems to the dial-in/out wide area network, or to an X.25 network or a 3270 gateway. (Different makes of terminal server offer different kinds of interconnection. Some can be ordered in different configurations based on customer need.) The use of a terminal server means that each terminal doesn't need its own network interface card or modem. The connection resources inside the terminal server are usually shared dynamically by all attached terminals.
Some terminal servers can be shared by up to 128 terminals. The terminals can be PCs, terminals that emulate 3270s, printers, or other devices with the RS-232/423 interface. In some terminal servers, the terminals can use TCP/IP for a Telnet connection to a host, LAT to a Digital Equipment Corporation host, or TN3270 for a Telnet connection to an IBM host with 3270 applications. With some terminal servers, a given terminal user can have multiple host connections to different kinds of host operating systems (UNIX, IBM, DEC).
The Microsoft Windows Terminal Server (WTS) is a server program running on its Windows NT 4.0 (or higher) operating system that provides the graphical user interface (GUI) of the Windows desktop to user terminals that don't have this capability themselves. The latter include the relatively low-cost NetPC or "thin client" that some companies are purchasing as alternatives to the autonomous and more expensive PC with its own operating system and applications. The Windows Terminal Server was code-named "Hydra" during development.
The Windows Terminal Server has three parts: the multiuser core server itself, the Remote Desktop Protocol that enables the Windows desktop interface to be sent to the terminals by the server, and the Terminal Server Client that goes in each terminal. Users will have access to 32-bit Windows-based applications. The new terminal devices are being made by a number of vendors, including Network Computing Devices and Wyse Technologies. In addition, users of existing PCs running Windows 95 and Windows 3.11 operating systems can also access the Server and its applications. The Terminal Server can also serve terminals and workstations that run UNIX, Macintosh, or DOS operating systems that can't be upgraded to 32-bit Windows.
Co-developed with Citrix, Microsoft's Windows NT 4.0 Terminal Server Edition together with Citrix's MetaFrame product replace Citrix's WinFrame product.