What Is Telnet?
Updated: March 28, 2003
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
Windows Server 2003 and Windows XP Professional include Telnet Client and Telnet Server, which allow users to make remote connections based on the Telnet protocol. Using Telnet Client and Server, you can create a remote command console session on a host. Using a local command prompt window, you can run command line programs, shell commands, and scripts in a remote command console session just as though you were locally logged on to the host. Thus, having Telnet client and server software solves two networking problems. It allows for interoperability between disparate operating systems, and it facilitates administration of remote systems, saving administrative time and network resources.
Telnet Client and Server are well suited for troubleshooting and configuring remote computers, especially in mixed environments that require interoperability between different operating systems. For example, you can use Windows Server 2003 Telnet Client to connect to a Telnet server that is running on another operating system such as UNIX. Likewise, you can use a Telnet client that is running on UNIX to connect to a computer running Windows Server 2003 Telnet Server. Telnet Client and Server are also ideal in situations where memory and processor resources are minimal on a client or host or where network bandwidth is limited. This is because computers running Telnet clients and servers use less memory and processor time than other remote management tools, and Telnet clients and servers transmit only plaintext (unencrypted characters) across the network.
Remote administration is a method of managing one or more remote computers from a single location. In a large organization, you can use remote administration to centrally manage hundreds or even thousands of computers located in other buildings or even in other cities. In a small organization, you can use remote administration to manage a single server located in an adjacent office.
By its nature, remote administration lowers the total cost of ownership (TCO) by making system management easier and more efficient. Using remote administration, server operators and technicians can manage and troubleshoot servers without having to locally log on to the server, thereby lowering the cost of on-site support. Remote administration also assists help desk technicians in solving problems more quickly by letting them take control of a user’s computer.
Telnet and Other Technologies
Telnet is closely related to two other technologies that provide an alternative for remote command console sessions, depending on your needs for distributed computing, security, configuration requirements, and so on.
Windows Server 2003 Terminal Services
Telnet and Terminal Services are similar in that they are both used for remote sessions. However, Terminal Services extends the model of distributed computing by allowing client computers to operate in a server-based computing environment. Whereas Telnet only allows terminal emulation between a Telnet server and client, Terminal Services running on Windows Server 2003-based computers allows clients to run applications, while data processing, and data storage occur on the server. Applications and user sessions are transmitted over the network and displayed via terminal emulation software. Similarly, print streams, keyboard input, and mouse clicks are also transmitted over the network between the server and the terminal emulation software. Each user logs on and sees only their individual session, which is managed transparently by the server operating system and is independent of any other client session. You might want to consider using Windows Server 2003 Terminal Services if you require more extensive distributed computing.
Windows Services for UNIX 3.5
Windows Services for UNIX 3.5 includes a Telnet character-mode client that provides functionality not included in Windows Server 2003. The Windows Services for UNIX character-mode client supports both stream mode and console mode. It also provides for logging and additional configuration settings.
Windows Services for UNIX 3.5 includes two Telnet servers:
The default, Windows-based Telnet server, which is functionally similar to the one included with all versions of Microsoft Windows since Windows 2000
The Interix telnetd
Only one of these Telnet servers can be enabled at a time. By default, neither Telnet server is enabled for security reasons.
The Windows Services for UNIX 3.5 Telnet server accepts logons from a variety of clients, including the Telnet clients shipped with Windows 2000, Windows NT, Windows 95, and Windows 98, as well as a variety of character-mode terminal clients from virtually any operating system. Additionally, it can be configured to meet specific site requirements to improve security, simplify logons, support stream or console mode, and so forth.
The Windows Services for UNIX 3.5 Telnet server should be familiar to users of Windows 2000, Windows XP, and Windows Server 2003. It is essentially the same as the server included in Windows XP Professional and Windows Server 2003, and it is very similar to the one included in Windows 2000 editions. It uses the Windows command shell (Cmd.exe) as the default shell. You can start and stop this server from either the Services MMC (Services.msc) or from the Windows Services for UNIX Administration MMC (Sfumgmt.msc). If you are using Windows and UNIX in a mixed networking environment, you might want to consider installing Windows Services for UNIX 3.5 to extend the capabilities of Telnet.