You can use Telnet to access other systems. These Telnet commands will help you do that.
Telnet is used from the command line, for example, the command prompt on Windows. Only one command is needed to start the client:
telnetYou can also connect directly without starting the client first. To do this, either specify the hostname or establish the connection via IP address:
telnet <hostname></hostname>
telnet 127.0.0.1You will now be asked to enter the access data and will then be connected.
The following overview shows the standard commands. Some of these can be extended with arguments and executed using the Telnet client:
| Command | Short command | Description |
|---|---|---|
| ?/help | ? | Opens the help menu |
| Close | c | Closes the current Telnet connection |
| display argument | d | Displays the various parameters for the current connection (port, terminal type, etc.) |
| environ argument | Defines the variables for the respective operating system environment | |
| toggle argument | Determines how Telnet reacts to certain situations. The command changes the status from TRUE to FALSE or vice versa; using set or unset, the status can also be set directly — arguments are thus also valid for set/unset | |
| Logout | Terminates the current Telnet session if the remote host supports the logout option | |
| mode type | Sets the transmission type (text file, binary file) | |
| open hostname | o | Establishes another connection to the selected host in addition to the existing one |
| Quit | q | Terminates the Telnet client including all active connections |
| send argument | sen | Sends selected typical Telnet strings to the host |
| set argument | set | Modifies the connection parameters |
| Unset | u | Loads the predefined connection parameters |
| Status | st | Shows whether the connection is active |
Since Telnet is operated from the command line, you should also know other commands. Get to know Windows CMD commands to easily find your way around the command prompt.
Some commands can be extended by arguments, which means that more options are available to you. Here are some important parameters:
| Command | Option | Description |
|---|---|---|
| telnet | -d | Activates debug mode |
| -a | Attempts automatic login | |
| -n tracefile | Opens tracefile to record appropriate information (see also “set tracefile”) | |
| -l user | If the host supports environ, you will be logged in as the specified user. | |
| -e escape char | Sets an escape character | |
| -E | No character is recognized as escape character | |
| -x | Attempts to activate encryption | |
| mode | character | Disables LINEMODE |
| Line | Enables LINEMODE | |
| isig/-isig | Enables/disables the TRAPSIG mode of LINEMODE | |
| edit/-edit | Enables/disables the EDIT mode of LINEMODE | |
| softtabs/-softtabs | Enables/disables the SOFT_TABS mode of LINEMODE | |
| litecho/-litecho | Enables/disables the LIT_ECHO-Modus of LINEMODE | |
| send | abort | Sends “Abort process” sequence |
| Ao | Sends “Abort output” sequence; the host flushes the output from itself to the client. | |
| ayt | Sends “Are you there” sequence; the host can confirm with a response. | |
| brk | Sends “Break” sequence | |
| ec | Sends “Erase character” sequence; the host erases the last character entered | |
| el | Sends Erase line sequence; the host erases the line that is being entered | |
| eof | Sends “End of file” sequence | |
| eor | Sends “End of record” sequence | |
| esc | Sends the current escape character (see also “telnet -e”) | |
| ga | Sends “Go ahead” sequence | |
| getstatus | Requests the host to discard any input that has not yet been processed | |
| ? | Provides information about the send command | |
| set/unset | echo value | Determines whether characters entered should also be displayed |
| (value can be TRUE/FALSE or a special character) | eof value | Enables the “End of file” character (see also “send eof”) |
| erase value | Enables erase character (see also “send ec”); works only in localchars mode (see also “toggle localchars”) | |
| escape value | Enables escape character (see also “telnet -e”) | |
| flushoutput value | Enables abort output character (see also “send ao”); works only in localchars mode (see also “toggle localchars”) | |
| lnext value | Enables “lnext” characters | |
| quit value | Enables “break” characters (see also “send brk”); works only in localchars mode (see also toggle localchars) | |
| reprint value | Enables “reprint” character | |
| start value | Enables “start” character; only if TOGGLE-FLOW-CONTROL is enabled | |
| stop value | Activates “stop” character; only if TOGGLE-FLOW-CONTROL is activated | |
| worderase value | Enables “worderase” characters | |
| environ | define variable value | Assigns a value to a variable; values can be enclosed in single or double quotes. |
| undefine variable | Deletes the specified variable | |
| export variable | Exports the specified variable | |
| unexport variable | Specifies that the specified variable may only be exported when Telnet is specifically requested to do so | |
| list | Lists all variables; * character indicates whether the variable is exported automatically. | |
| ? | Provides information about the send command | |
| toggle | autosynch | If both autosynch and localchars are active, an additional “synch” sequence is sent when the quit character is sent (see also “set quit”) |
| (Initial state is TRUE) | binary | Enables/disables “binary” option on input and output |
| inbinary | Enables/disables “binary” option at input | |
| outbinary | Enables/disables binary option on output | |
| crlf | TRUE: carriage return is set to <CR><LF> | |
| crmod | FALSE: carriage return is set to <CR><NUL> (FALSE is the normal state here) | |
| debug | Switches the state of the “carriage return” mode | |
| localchars | Switches the state of the “Socket debug” mode (FALSE is the normal state here) |
For more Telnet commands and options, as well as detailed documentation, check out the Telnet Man Page.
If you don’t really know the remote protocol yet, it’s worth taking a look at our detailed article on the subject — telnet. The article also explains how to enable Telnet in Windows.
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