InterAccess Telnetd Server

As Windows NT Server spreads out into UNIX network environments, the demand for remote command-line access to an NT system has increased. Although you can implement remote command-line access in many ways, one of the most popular methods in the UNIX world is through Telnet. Telnet provides a simple, character-mode connection into an operating system. NT Server 3.51 and NT Server 4.0 do not include native support for a Telnet server service; however, several third-party vendors offer Telnet server products. Pragma Systems is one of those vendors, and its product, InterAccess Telnetd Server, offers several interesting features for NT servers and workstations.

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

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

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

Once you log on via the Telnetd service, your Telnet client software, not the Telnetd service, determines your capabilities. To illustrate this point, I used both Microsoft's standard Telnet client to access the Telnetd service and Attachmate'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. In contrast, the VT340 client delivers an environment that closely matches the console 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 receive the display correctly.

Keyboard mapping is a little awkward. The Telnetd service supports arrow keys and function keys, but not the Alt key. By default, the Telnetd service uses the Esc key to simulate the Alt key. Thus if you want to press Alt+F in the EDIT program, you press Esc followed by F. Most Telnet clients (not including Microsoft's) support keyboard mapping, so you can change key assignments other than the Alt key. On a related note, Pragma has released a console Telnet client implementation as part of InterAccess Companion that lets you use the Alt key natively.

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

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