TELNET – Windows CMD Command
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Communicate with another host using the TELNET protocol.
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Syntax TELNET [-a] [-e escape_char] [-f log_file] [-l user] [-t term] [host [port]] Key -a Attempt automatic logon Same as -l except uses currently logged on user name -e Escape character to enter telnet client prompt. -f Filename for client side logging. -l The username to login with on the remote system. Requires that the remote system support the TELNET ENVIRON option. -t The terminal type: vt100, vt52, ansi or vtnt. host The hostname or IP address of the remote computer. port A port number or service name. |
In Windows 7 and above the telnet client is not enabled by default.
To enable it open ‘Programs and Features’ | ‘Turn Windows features on and off’ and select Telnet Client.
or run
pkgmgr /iu:”TelnetClient”
In Windows 2008 and above the telnet server is not installed by default.
To enable it open Server Manager | Features | Add Features and select ‘Telnet Server’ and install.
or run Install-WindowsFeature or
ServerManagercmd -install telnet-client
Telnet commands
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close Disconnect from an existing Telnet connection. display Show the current settings for Telnet Client. open Use open hostname to establish a Telnet connection to a host. quit Disconnect from the remote server (if connected) and close the Telnet Client. send Send commands to the Telnet server. send ao Abort Output command. send ayt "Are you there?" command. send esc Sends the current escape character. send ip Interrupt process command. send synch Perform a Telnet synch operation. send brk Send a break signal. set Configure the Telnet Client for the current session: set bsasdel Backspace will be sent as delete set codeset option Available only when the language is set to <a href="https://go.microsoft.com/fwlink/?LinkId=108380">Japanese</a>. set crlf Set new-line mode; causes the RETURN key to send the combination of carriage return and line feed: 0x0D, 0x0A. When turned off, it sends only the carriage return character, 0x0D. set delasbs Delete will be sent as backspace. set escape character Specifies the character that will switch from Telnet session mode to the Telnet command mode. From command mode, press ENTER to return to session mode. set localecho Turn on local echo. All characters typed will be displayed on the local console. Remote Telnet servers usually send each character typed back, so setting this option could result in duplicate characters displayed for each one typed. set logfile name The name of the Telnet log file for this session, also turns on logging. The default path is your current directory. set logging Turn on logging for this session. Set mode console Change the mode of operation to console mode (default). Setting the mode to console causes Telnet server to include ANSI or other escape commands to control cursor positioning within a fixed window of x rows and y columns. Set mode stream Change the mode of operation to stream mode. Setting the mode to stream turns off the ANSI or other escape commands that attempt to control cursor placement or clearing the screen. Stream mode is useful when you do not want the Telnet client to emulate a terminal. The output is sent as if there is no terminal window with x rows and y columns. Some applications that use Telnet for file transfer fail to work correctly when console mode is enabled. set ntlm Turn on NTLM authentication. set term {ansi | vt100 | vt52 | vtnt} The type of terminal to emulate. status Determines whether the computer running Telnet Client is connected. unset Turns off an option previously set by using the set command. ?/help Display Help. ?/set Display Help information for the set command. |
Anything other than one of the commands above will be sent as a string to the Telnet server.
For example, send ss64 sends the string ss64 to the Telnet server, which echoes the string in the Telnet session window.
Telnet communicates with the peer (telnet server) in clear text which is a potential security hazard for machines connected to the internet. Telnet traffic can be secured with Internet Protocol security (IPsec)
A alternative to telnet is SSH (which is cross platform) a popular choice on Windows is PuTTY: A Free Telnet/SSH Client.
Ports
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20 & 21 File Transfer Protocol (FTP) 22 Secure Shell (SSH) 23 Telnet remote login service (the telnet client default) 25 Simple Mail Transfer Protocol (SMTP) 53 Domain Name System (DNS) service 80 Hypertext Transfer Protocol (HTTP) used in the World Wide Web 110 Post Office Protocol (POP3) 119 Network News Transfer Protocol (NNTP) 143 Internet Message Access Protocol (IMAP) 161 Simple Network Management Protocol (SNMP) 194 Internet Relay Chat (IRC) 443 HTTP Secure (HTTPS) 465 SMTP Secure (SMTPS) |
Examples
Connect to the remote webserver for future4tech.com through HTTP port number 80 and retrieve the home page, note the GET command is case sensitive:
C:\> telnet future4tech.com 80
GET /index.html
<line feed>
Run a telnet script using the freeware Telnet scripting tool, in the script file use \m for a carriage return/linefeed:C:\utils\TST10.exe /r:MyTelnetScript.txt /o:output.txt
