InterAccess Telnetd Server

Pragma's Telnet server supports a variety of remote command-line applications

As Windows NT Server spreads out into UNIX network environments, the demandfor remote command-line access to an NT system has increased. Although you canimplement remote command-line access in many ways, one of the most popularmethods in the UNIX world is through Telnet. Telnet provides a simple,character-mode connection into an operating system. NT Server 3.51 and NT Server4.0 do not include native support for a Telnet server service; however, severalthird-party vendors offer Telnet server products. Pragma Systems is one of thosevendors, and its product, InterAccess Telnetd Server, offers several interestingfeatures for NT servers and workstations.

The InterAccess Telnetd Server is available for Intel, Alpha, and PowerPCplatforms. My unlimited license version of the product contained diskettes forall three environments. A graphical Setup program accommodates installation, andTelnetd includes an uninstall program. In general, the installation process ispainless. Printed documentation is sparse, but the product includes online Helpand FAQ files.

The InterAccess Telnetd Server does not add the Telnetd service to the NTservice set. Instead, the program adds an Inetd service, which automaticallylaunches the Telnetd service when the system receives an inbound Telnetconnection. The Inetd service also launches Pragma's Telnetd Manager (forviewing and controlling Telnet sessions) on demand. You can modify Inetd tolaunch other TCP/IP programs as well. The use of Inetd as a launching mechanismis a tried-and-true approach in the UNIX environment; with Inetd you can run therelatively small Inetd service (39KB) all the time instead of the larger Telnetdservice (96KB) or Telnetd Manager (315KB).

Pragma's Telnetd module uses standard NT security to authorize Telnetlogons. As shown in Screen 1, when you connect to the Telnet Server, Telnetdprompts you for a login name, password, and domain. If you don't include adomain name, Telnetd authenticates the user and password from the server's localsecurity database. Please note that the Telnet client transmits the password toTelnetd as clear text--an obvious security exposure. The use of clear textbetween Telnet clients and servers is a generic problem in most Telnet serverproducts; Pragma is not alone here.

Once you log on via the Telnetd service, your Telnet client software, notthe Telnetd service, determines your capabilities. To illustrate this point, Iused both Microsoft's standard Telnet client to access the Telnetd service andAttachmate's VT340 Telnet implementation (included in Attachmate's EXTRA!Personal Client product). As you can see in Screen 2, the Microsoft client(foreground) provides only a rudimentary interface to the DOS EDIT program. Incontrast, the VT340 client delivers an environment that closely matches theconsole command-line interface because it supports colors and video highlights.Note that you must enable a PC-based font set in the Telnet client to receivethe display correctly.

Keyboard mapping is a little awkward. The Telnetd service supports arrowkeys and function keys, but not the Alt key. By default, the Telnetd serviceuses the Esc key to simulate the Alt key. Thus if you want to press Alt+F in theEDIT program, you press Esc followed by F. Most Telnet clients (not includingMicrosoft's) support keyboard mapping, so you can change key assignments otherthan the Alt key. On a related note, Pragma has released a console Telnet clientimplementation as part of InterAccess Companion that lets you use the Alt keynatively.

During my testing, I ran into only two significant problems. First, when Iused Telnet to run the full-screen EDIT application, the NT ntvdm.exe processran up to 98 percent of CPU utilization whenever I was typing. And despite thatheavy CPU utilization, response time was miserable. The second problem Iencountered was that I could not run the vi editor included in MicrosoftWindows NT Server Resource Kit CD-ROM. Pragma explained that this problem isa result of how Microsoft handles screen buffers (a Telnetd update will fix theproblem) and said that other vendors' vi implementations would run fine. Thebottom line here is that you need to thoroughly test any full-screenapplications you want to use before you deploy this product.

All things considered, I was very impressed with Pragma's InterAccessTelnetd Server. It is easy to install and easy to manage, and it accommodates avariety of Telnet clients. With support for full-screen applications and consolefeatures such as command-line recall (via the Up/Down arrow keys), Telnetdprovides a remote command-line interface that you can adapt to easily.