Tag: Interactive

Today marks the last post in my Telnet series unless someone writes with additional ideas on issues they’d like me to cover. So far, I haven’t received any requests for Telnet scripting topics, so I’ve decided that perhaps there isn’t a lot of interest in this topic. I discussed basic Telnet connectivity in the Using Telnet to Perform Tasks post. The last post, entitled “Sniffing Telnet Using Wireshark,” covered Telnet security issues. Today’s topic is a natural extension of the topics discussed so far—now that you have an interactive session with a remote system (router, server, or workstation, it doesn’t matter), what can you do with it?

My book, “Administering Windows Server 2008 Server Core,” provides a few ideas on the topic, but not very many. I’m thinking now that perhaps I should have discussed this topic in “Windows Command-Line Administration Instant Reference,” but then there is always the question of the cost to other topics and I had no idea when I wrote that book that Telnet was still so popular with some administrators. The short answer is that you have a fully functional command prompt.

The problem is that you’re working with a remote command prompt, not the local command prompt. So, the command prompt you’re accessing is the one on the remote system, with all its attendant resources and limitations. As a consequence, unless you’re working with that system every day, you’ll want to type Ver and press Enter to see which version of the command prompt you’re using. It seems like a simple thing to do, but some administrators don’t and later discover that problems at the command line had nothing to do with the session, but the version of the command line. If you’re working with Windows, you can find a complete list of Windows OS Version numbers on MSDN.

Knowing the version number and the associated operating system name lets you look for commands for that OS in either of my books or you can look them up online. For example, you can use the search phrase, “Windows XP Command Line” on Google (or any other search service) to obtain quick access to sites such as Technet where you can find a listing of associated commands from A to Z. Obviously, these sites will only tell you which commands are available, not how to use them, but knowing what’s available does help.

Another problem that many administrators encounter is that they don’t consider the environment. Again, the environment focuses on the remote system, not your local machine. So, that favorite path might not be part of the Path environment variable and typing a much beloved command won’t work at all. Consequently, it pays to type Set | More and press Enter so that you can look through the environment variables to ensure everything you need is available. This command also provides some essential cues about the remote system configuration. For example, if the Set command reveals a ProgramFiles(x86) environment variable, then you know you’re working with a 64-bit system and some older commands may not work as anticipated. Use the Set command to add or modify any environment variables required to get your work done.

At this point, you know which commands you can execute and you know that the environment is configured for use. What you don’t know is whether you have the rights required to accomplish the task. You can use commands such as ICACLS to verify your rights or you can simply try the command to see whether it completes successfully. The important thing to keep in mind is that newer versions of Windows employ the UAC, even at the command line, so you might find your efforts thwarted.

Even when everything is working properly and you have all of the required rights, you should avoid using certain commands in a remote session. For example, you definitely don’t want to start another copy of Telnet from the remote session (assuming the remote session will even allow it). Using the WinRS command probably won’t work well either. However, Terminal Server commands such as QWinSta appear to work just fine. Let me know your thoughts about Telnet at [email protected].

 

The previous post in this series, Configuring Telnet, helped you get Telnet set up on a system. Now that you have Telnet installed, you can use all of the command line and interactive features described in “Administering Windows Server 2008 Server Core“ to access it. For example, you can simply type Telnet <Name of Server> and press Enter to start a session with that server. Because of the way Telnet works and the commands that you’ll issue, it’s always a good idea to use an Administrator command line when working in either Vista or Windows 7. To open such a command line, you choose Start > All Programs > Accessories, right click the Command Prompt entry, and choose Run As Administrator from the context menu. You may have to supply a password to gain administrator access.

When you plan to work with Telnet for an extended period, you might find the interactive environment more suited to your needs. To enter the interactive terminal, you simply type Telnet and press Enter. This action places you at the Microsoft Telnet prompt, but doesn’t open a connection for you. Type ? and press Enter to see a list of available commands as shown here.

One of the advantages of using the interactive prompt is that you’ll find it easier to configure Telnet options. To see these options, type Set ? and press Enter. For example, if you want to make your Telnet session a little more secure (and the emphasis is on little), type Set NTLM and press Enter. Some settings are a toggle. For example, if you want to remove NTLM authentication, you type Unset NTLM and press Enter. Type Unset ? and press Enter to see a list of toggled settings. Here is a list of the settings available when using the Windows 7 version of Telnet (your version of Telnet might vary).

The ability to set or reset settings is nice, but it would also be nice to know how Telnet is configured. To obtain this information, you type D (for display) and press Enter. You’ll see a list of configured settings. The default settings depend on your version of Windows and how you configured Telnet in the past. If you don’t see a particular setting, it means that the setting either isn’t configured or is toggled off (unset).

 

Simply configuring a setting doesn’t guarantee that Telnet will use it. The server determines whether a particular setting is valid. For example, you can request NTLM authentication, but the authentication won’t occur if the server doesn’t support it. Likewise, your choice of terminal is sent to the server, but the server ultimately chooses the terminal type, which is going to be ANSI in most cases.

 

To create a connection in interactive mode, you type O <Name of Server> and press Enter. You may see a warning message about sending your password in the clear. Type Y and press Enter. At this point, you’ll see the standard Telnet prompt at the server. To regain access to the client side prompt, you press a control key combination. The default is Ctrl+]. This will take you back to the client Telnet prompt where you can enter additional commands. When you want to go back to the server side, simply press Enter twice.

To check your connection, type St and press Enter. You can also ask the server questions, such as “are you there” using the Sen command. To see all of the send options, type Sen ? and press Enter. The help list shows those commands that Telnet definitely supports. However, the Knowledge Base article entitled, “The TELNET Protocol” seems to tell a different story (I’ll check out these additional commands for a future post). For the sake of doing something interesting, try typing Sen AYT (for are you there) and press Enter. Here is typical output from this command.

Now that you’ve asked for information, press Enter twice to see the server’s response. In most cases, you’ll see YES as shown here.

You have several ways to close a connection. However, for this session, press Ctrl+] to return to the Telnet client session. Type C and press Enter. The connection is now closed. To verify this fact, type St and press Enter. Type Q and press Enter to leave the Telnet interactive environment. Now, here’s the interesting part of all this. You can also script this sort of behavior to make many tasks automatic. A future post will also pursue this topic in more detail. For now, let me know if you have any questions about the basic interactive session at [email protected].