Windows – abort telnet while it is still trying to connect

telnetwindows

At times I find myself telnetting from Windows XP to another server and that I state a wrong port number such as

c:\> telnet xxxxx.yy pp

After hitting Enter, I realize that I entered the wrong port number and would like to abort the telnet process with a ctrl-c, however, telnet doesn't seem to respond even to ctrl-c. So, I have to wait a few seconds until telnet returns with a

Connecting to xxxxx.yy... 
Could not open connection to the host, on port pp: Connect failed

It's rather annoying to wait for the error message, especially when I already know it will eventually come.

So, is there a way to immediately stop the telnet process?

Best Answer

Edit: Of course, it's never that simple. As you've observed, Microsoft's telnet doesn't respond to ^] while waiting for a connection.

If you don't want to wait around, you only have two options:

Kill the telnet process (from another command shell or the task manager), or
Use another telnet client. PuTTY is a good choice, since it will launch as a separate window; even if you get the port wrong and the PuTTY window freezes, your command shell will be available to launch another instance with the correct port number.

Use the escape character (defaults to Ctrl+]). This brings up a telnet prompt at which you can close or quit the connection.

> telnet

Welcome to Microsoft Telnet Client

Escape Character is 'CTRL+]'

Microsoft Telnet>

You can change this to nearly anything you like on your commandline by using the -e flag:

C:\>telnet /?

telnet [-a][-e escape char][-f log file][-l user][-t term][host [port]]
[...]
 -e      Escape character to enter telnet client prompt.
[...]

C:\>telnet -e '

Welcome to Microsoft Telnet Client

Escape Character is '''

Microsoft Telnet>

Related Solutions

Windows – Cannot connect to telnet server

Have you tried disabling the auto-tuning diagnostic in Windows 7?

netsh int tcp set global autotuninglevel=disabled

Microsoft Support KB article:

When the receive window autotuning feature is enabled, older routers, older firewalls, and older operating systems that are incompatible with the receive window autotuning feature may sometimes cause slow data transfer or a loss of connectivity.

The default auto-tuning level is "normal", and the possible settings for the above command are:

disabled: uses a fixed value for the tcp receive window. Limits it to 64KB (limited at 65535).
highlyrestricted: allows the receive window to grow beyond its default value, very conservatively
restricted: somewhat restricted growth of the tcp receive window beyond its default value
normal: default value, allows the receive window to grow to accommodate most conditions
experimental: allows the receive window to grow to accommodate extreme scenarios (not recommended, it can degrade performance in common scenarios, only intended for research purposes. It enables RWIN values of over 16 MB)

Ping works while telnet fails

To telnet from a Windows computer to a Unix computer you need to ensure that

Windows has telnet client installed (it is not installed in latest Windows)
Windows firewall is not blocking outgoing Telnet (very unlikely)
Windows can resolve server's name (e.g. through DNS or local hosts file)
Unix server has Telnet service enabled (increasingly being disable to encourage SSH use)
No intermdiate firewalls are blocking Telnet (unlikely if both computers are in same subnet)
You have valid Unix login credentials (user name and password)

Since you didn't post an actual error message but just said you "can't do telnet" - we can only guess at the problem.

To check if the Telnet service is runnning, log on at the Unix server console and use this command:

netstat -a | grep "telnet.*LISTEN"

The output should be this

tcp        0      0  *.telnet               *.*                    LISTEN

Note: If you have problems, update your question with the actual command and error messages by using cut & paste (then edit only if needed to change confidential details)

Update:

Redhat / Fedora

Use these commands

chkconfig telnet on
chkconfig --list | grep telnet

The output from the second command should be

   telnet: on

Ubuntu

sudo apt-get install telnetd
sudo /etc/init.d/inetd restart

Once installed, from the GUI, select Administration, Services and enable Telnet

Distros using Xinetd

You need a file named /etc/xinetd.d/telnet with contents something like this

# default: on
# description: The telnet server serves telnet sessions; it uses \
#       unencrypted username/password pairs for authentication.
service telnet
{
        flags           = REUSE
        socket_type     = stream
        wait            = no
        user            = root
        server          = /usr/sbin/in.telnetd
        log_on_failure  += USERID
        disable         = no
}

Warning!

You shouldn't be doing this unless you are familiar with Linux, with Linux commands, with editors such as vi and have good backups and are prepared to reinstall if it all goes horribly wrong. If other people rely on this server, you should employ a systems administrator who is familiar with the particular Linux distribution you are using.