how do I make sure the port is opened

[Hanry Zhou]

Hi,

we are trying to telnet to a port to confirm if the port is opened or not:
telnet a.b.c.d port#
but always getting "connection refused" message. However, when I run lsof or netstat -a , I don't see this particular port is using.

Is this correct way to test if the port is running or not.

[Alex Lavrov.]

well, telnet is executed by inetd, so only when it's beeing made a connection to the port, there is actually telnetd is executed. when there are no attempts, the port is not in use, that's why you don't see anything.

You should check if telnetd presents in /etc/inet.d file.

[Uday_S_Ankolekar]

Is that prot listed in /etc/services file?

-USA..

[Rick Garland]

A neat utility for finding out open ports is called "nmap". Available from porting archive,
http://gatekeep.cs.utah.edu

Can install on your local system and run 'nmap localhost' The output will be the open ports on the localhost system.

[Hanry Zhou]

the port is not being used as far as I can see by lsof and netstat -a. However, the question is when we run "telnet ip 7003", we got connection refused. What does that mean? do that mean that the port is not opened on the server ?

[Alex Lavrov.]

If the program that must handle this port listed in /etc/inetd.conf and /etc/services, you won't see it with lsof, because it will be brought up by inetd, only when this port is accessed (that's the idea).

If it's stand alone daemon and you don't see any binds to this port, it means the daemon is not running.

[Rick Garland]

The port 7003 on IP is not accepting telnet connections. Could be open for other types of connections but not telnet

[Biswajit Tripathy]

If your "netstat -a" shows that the port is in LISTEN
state in the server, but still you get connection refused
message in the client, then chances are there is a
firewall running which is blocking the connection AND
replying with "connection refused" message.

- Biswajit

[Mel Burslan]

also make sure that, the host you are coming from is not in the list of hosts blocked by any rule in the /etc/inetd.sec file if all other settings seems to be in correct order.

[Ermin Borovac]

"Connection refused" usually means that no program is listening on the port. You can say that port is opened (i.e. not blocked by firewall or similar), but not used.