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Title A class to communicate via Telnet.
Summary This note provides a class that can be used to establish and communicate with a Telnet server.
Contributor Tim Slattery
Published 1-Mar-2001
Last updated 1-Mar-2001
Page rating   80% for 10 votes Useless Brilliant
 Download Telnet files - 9 Kb


CHookup allows a C++ program to initiate a Telnet connection to another computer. The program can then send commands and retrieve the results of those commands. CHookup works well with the Sun Solaris system. I've had it connected to a Linux system, but since I no longer have access to a Linux system, I make no guarantees. I've had reports of problems with other systems, but I haven't had time or resources to track them down.

Any such problems probably centre in the negotiation phase (CHookup::TelNetOpts). When the connection starts the two computers negotiate to decide which will do what (will I echo, will you echo, what terminal type are you, etc). Different systems do this somewhat differently. Since I've had access to Solaris machines, I've made the negotiations work with them. Other systems may require tweaks in TelNetOpts.


When CHookup's constructor runs, it looks for a file named hookup.ini. This file can be used to specify a logging file. If it exists, it looks like this:


You can use any filename in place of c:\hookup.log, of course. If the constructor finds this file, all data sent to and received from the remove computer will be written to this file. If the file already exists, the new data will be appended to the end. The log file should be used only for debugging! If you create hookup.ini and forget about it, the log file will continually grow, eating disk space and slowing execution of CHookup functions.

Implemenation note

This class does not use CSocket, instead it calls wsock32.dll functions. That means that you will have to add wsock32.lib to your project to compile it.

I don't have anything against CSocket. This class was originally a DLL. The DLL was written in C (not C++), and therefore did not use CSocket. Rather than implement CSocket and rewrite all the wsock32 calls, I took the easy way and left those calls alone.


CHookup::CHookup(bool bMessages)

The constructor takes a boolean argument. If "true", then error messages will be displayed in message boxes. If "false" messages will not be displayed. (I used CHookup in an ISAPI DLL. In that environment, trying to display a message box causes the server to hang. That's the reason for this argument.)

bool CHookup::Login(CString sHost, CString sUser, CString sPassword)

Login establishes a connection to a host. The return value is "true" if a connection was made, "false" if it failed.

CString CHookup::DoCommand(CString sCommand)

sCommand is sent to the remote host, and the result is returned. sCommand must be terminated with "\n" (newline character).

There is no "logoff" method. The class destructor ends the connection.

Usage normally looks something like this:

CHookup      TN;
CString      sResult;

TN.Login("host", "user", "password");  /* supply the right values, of
                                          course */

sResult = TN.DoCommand("ls\n");    /* sResult now has the result of the
                                      "ls" command, v=followed by a
                                      prompt. Note that the command is
                                      terminated by a newline.  */
Comments Date
...thats cool... 4-Mar-2004 Matt
im just starting c++ now, i havnt ever used the language before...im 15...and this lesson on how to make a telnet communicator makes it look easy!
im gonna try it!.
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