How to solve the telnet exit problem under CentOS

Recently, some CentOS users reported that after using telnet to connect, they found that it was a Windows firewall problem. However, after successfully connecting using the telnet command, they found that they could not log out. What should I do? The following editor will introduce to you the telnet logout failure under CentOS. solution. Let’s go and see it together!

How to exit from telnet in Linux

1.ctrl ] quit

Telnet is often used to test whether the port is open normally.

But there is a problem that everyone may encounter. After telnet enters a certain port, it cannot exit. There is no way. In order to continue testing, I have to close the dos (or other) window and reopen another one. Here is a method, hold down ctrl ] to exit to the normal telnet operation interface

Welcome to Microsoft Telnet Client

Escape Character is 'CTRL ]'

(Microsoft)Telnet>

Then enter quit to exit completely.

2. Simple usage of Telnet:

First, build a Telnet server. In the past, in order to make the machine faster, some unused services were turned off.

Enable your own Telnet in "Control Panel"-"Management"-"Service", and enter the user name and password you want the client to enter in the login tab, then OK, the Telnet server is set up

Test it on your own machine. In the command line, enter the Telnet local IP to enter, and then enter the user name and password step by step.

If you want to exit, press "Ctrl ]", and then exit via quit.

3. The second method of running the telnet program:

Enter command: telnet

The program is running at this time, but no connection is made (because the host is not specified)

Then the screen displays: telnet>

This is the telnet prompt. It indicates that the telnet program has been running and is waiting for the user to enter the command to use telnet. If you want to connect to a remote host, use the open command, that is, enter the command open and attach the host. network address, such as

telnet> open dns.hunu.edu.cn

The connection effect is exactly the same as the first method

4. How to log in to a system via telnet?

A: The original telnet login method can be implemented on the command line. For example, enter telnet www.lqqm.net on the windows command line to log in to this site. Enter telnet www.yjrg.net to log in to BBS. Suggestions Download and use dedicated telnet login tools, such as cterm, sterm, and fterm. I have used all three for a while and feel that cterm is the best; other professional telnet login tools include secureCRT and so on. It should be noted that the telnet command uses the UDP protocol, and SSH uses the TCP protocol. The essential difference between the two determines that the telnet login speed is faster than the SSH login, but the SSH login is more secure than the telnet login (the password will generally not be deciphered) , the relationship between the two is just like the relationship between ftp and tftp.

Telnet automatically exits after idle timeout

Set the telnet connection to automatically exit the current session after it has been idle for a certain period of time

Set parameter TMOUT, time unit: seconds (s)

For example:

TMOUT=21600, the telnet connection will be automatically disconnected after being idle for 6 hours.

You can set global TMOUT in /etc/profile or users can set TMOUT in .profile in their home directory.

When the idle time reaches the set value, the screen displays

timed out waiting for input: auto-logout

And disconnect the current telnet connection

View the TMOUT value of the current session

echo $TMOUT

This function is disabled when TMOUT is not set or TMOUT=0 is set.

What to do if telnet fails to exit under CentOS

Can’t exit! Ctrl c, Ctrl z, ESC, q, quit, exit, none of them work;

Pay attention to the information output after the telnet connection is successful:

Escape character is ‘^]’.

Ctrl ]

The method is finally right;

telnet》?

Commands may be abbreviated. Commands are：

close close current connection

logout forcibly logout remote user and close the connection

display display operating parameters

mode try to enter line or character mode (‘mode ?’ for more)

open connect to a site

quit exit telnet

send transmit special characters (‘send ?’ for more)

set set operating parameters (‘set ?’ for more)

unset unset operating parameters (‘unset ?’ for more)

status print status information

toggle toggle operating parameters (‘toggle ?’ for more)

slc change state of special characters (‘slc ?’ for more)

z suspend telnet

! invoke a subshell

environ change environment variables (‘environ ?’ for more)

? print help information

telnet》 close

Connection closed.

Enter question mark and press Enter to view help;

Enter close or quit and press Enter to exit telnet;

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