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Posted 24 Oct 2007

MFC Telnet Application

, 8 Nov 2007
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The article demonstrates an MFC GUI Telnet application with server capabilities for incoming connections support.


I've developed a Telnet application for implementing manual connection and data sending capabilities to Internet servers. You may use it for text mode Internet protocols (SMTP, POP, HTTP, WHOIS etc.) for sending, retrieving emails, whois queries, and so on. The application also allows opening ports on local computers for incoming connections.


You need an understanding of Internet protocols to be able to connect to servers and implement commands. Have a look at the corresponding RFCs available online.

Using the code

Click the first red button on the toolbar (CTRL+N) to connect to an Internet server on a particular port.

connect to server

The server address combo box is filled with predefined addresses, loaded from a hosts file present in the same directory as the Telnet application. After being connected to the server, you may send text messages to it. Click the INS key button in the text view, type in the command you want to send (if it won't fit in one single line, press ENTER to move the caret to the next line; also, in the multi-line text messages, end the last string you typed with an ENTER, and press ESC to send it), then press the ESC key to send the data you typed in. Wait for the response from the server.

This one provides an example output of a whois query on port 43:

whois query

whois query

In case of getting disconnected, press CTRL+R to redial connection to that server.

To listen on a particular port, press CTRL+L and enter the port you want to open:

listen on port

Try to open port 80 and enter in your IE browser while disconnected from the Internet. You will get a message similar to that appearing in the text view. You may send a reply to the IE browser with the same mode as I described before (INS, type the text message, ENTER, ESC).

IE connection

The client part is implemented with the CClientDoc, CClientView pair and the server part with the CServerDoc, CServerView pair.

There is one additional class in the project I developed:

  • Socket
  • It actually wraps WinSock functions for creating a socket, connecting to the server, sending and receiving data, and listening on a port. Have a look at the socket.h header.


This article, along with any associated source code and files, is licensed under The GNU General Public License (GPLv3)


About the Author

Chesnokov Yuriy
Russian Federation Russian Federation
Highly skilled Engineer with 14 years of experience in academia, R&D and commercial product development supporting full software life-cycle from idea to implementation and further support. During my academic career I was able to succeed in MIT Computers in Cardiology 2006 international challenge, as a R&D and SW engineer gain CodeProject MVP, find algorithmic solutions to quickly resolve tough customer problems to pass product requirements in tight deadlines. My key areas of expertise involve Object-Oriented
Analysis and Design OOAD, OOP, machine learning, natural language processing, face recognition, computer vision and image processing, wavelet analysis, digital signal processing in cardiology.

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Comments and Discussions

GeneralERROR - Your telnet client rejected our request to use char-at-a-time mode! Pin
Member 223391512-Oct-09 17:54
memberMember 223391512-Oct-09 17:54 
AnswerRe: ERROR - Your telnet client rejected our request to use char-at-a-time mode! Pin
Chesnokov Yuriy12-Oct-09 19:09
memberChesnokov Yuriy12-Oct-09 19:09 
QuestionHow to get whois query output? Pin
Priya_Sundar30-Oct-08 22:30
memberPriya_Sundar30-Oct-08 22:30 
AnswerRe: How to get whois query output? Pin
Chesnokov Yuriy31-Oct-08 1:13
mvpChesnokov Yuriy31-Oct-08 1:13 
QuestionHow to add the source code in project? - No .dsp or .dsw files. Pin
Priya_Sundar29-Oct-08 20:06
memberPriya_Sundar29-Oct-08 20:06 
AnswerRe: How to add the source code in project? - No .dsp or .dsw files. Pin
Chesnokov Yuriy29-Oct-08 20:22
mvpChesnokov Yuriy29-Oct-08 20:22 
GeneralRe: How to add the source code in project? - No .dsp or .dsw files. Pin
Priya_Sundar30-Oct-08 18:42
memberPriya_Sundar30-Oct-08 18:42 
Generalgood work. can u send to me.full source plz.. Pin
ox1111@paran.com25-May-08 18:11
memberox1111@paran.com25-May-08 18:11 
AnswerRe: good work. can u send to me.full source plz.. it's in Pin
Chesnokov Yuriy26-May-08 20:57
mvpChesnokov Yuriy26-May-08 20:57 

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