I am using Linux server in my testing envoirnment. I am using Redhat 6.2 version and due to other apps, I am not able to upgrade to latest version.

My tests will telnet into the server several times, but after some time I see that the server will stop responding to the telnet requests. If I restart the inet services, problem will be solved for some time but I will eventually run in to again.

If I reboot the system, I don't see the problem for some time. When in that state, I do not see anything in the log messages. I also do not see telnet port in the listening mode.

Is there any file or secuirty feature that I have to disable to allow unlimited telnet requests on the server ??

You don't see anything listening because of inetd (or xinetd). Basically many services don't need to run all the time so inetd keeps track of the various ones available and only on a request for the specific service does it acually start it.

On my RH it is xinetd but I don't have anything as old as 6.2.
If its inetd you can look at /etc/inetd.conf.
If its xinetd you can look at /etc/xinetd.d/telnet.

Both will show you configuration options but I don't know of one that would do what you're talking about - it may become apparent if you look at the files. It also may not be telnetd itself that is the issue but rather some PAM or other authentication setup that is shutting you down because it thinks multiple logins at the same time are some sort of attack.

Below is the output from the /etc/inetd.conf file on the server. Am I missing any entries here ??


# These are standard services.
#
ftp stream tcp nowait root /usr/sbin/tcpd in.ftpd -l -a
telnet stream tcp nowait root /usr/sbin/tcpd in.telnetd
#
# Shell, login, exec, comsat and talk are BSD protocols.
#
shell stream tcp nowait root /usr/sbin/tcpd in.rshd
login stream tcp nowait root /usr/sbin/tcpd in.rlogind
#exec stream tcp nowait root /usr/sbin/tcpd in.rexecd
#comsat dgram udp wait root /usr/sbin/tcpd in.comsat
talk dgram udp wait nobody.tty /usr/sbin/tcpd in.talkd
ntalk dgram udp wait nobody.tty /usr/sbin/tcpd in.ntalkd
#dtalk stream tcp wait nobody.tty /usr/sbin/tcpd in.dtalkd
#
# Pop and imap mail services et al
#

Your telnet entry look OK. Don't see anything there that would cause a timeout. It must be some other "feature" on your system.

FYI: Rather than rebooting doing a "kill -1 <PID>" on the Process ID of inetd (ps -ef |grep inetd" to find it) will cause inetd to reread inetd.conf - this may also reset whatever it is back to square one for you.