Using Telnet to Test Port Functionality

List of all ports : http://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers

[root@ibsvr ~]# Telnet tserv 22OR,[root@ibsvr ~]# telnet 192.168.1.12 22

where "tserv" is the target host name of your Terminal Server. 

Note : No need to run TELNET/xinetd service of the TARGET HOST server .  

If telnet is successful, you simply receive the telnet screen and a cursor. On the Terminal Server, Terminal Server Administration will show a blue computer icon with no other information. The Telnet connection will also consume an idle session. 

The Terminal Server should disconnect the connection after a few minutes. Or, you can disconnect using Telnet. 

This test tells you that you can connect over the port. 

If Telnet reports that you cannot connect, there are several possible reasons: 


If you can connect by replacing "tserv" with the Terminal Server's IP address but not the host name, you may have a DNS or WINS resolution problem.
If you can connect when "tserv" is the host name, but cannot connect when "tserv" is the computer name, then you may have a NetBIOS name resolution issue with WINS or an LMHOSTS file.
If you cannot connect when "tserv" is the IP address, the host name, or the computer name, then it is likely that port 3389 is blocked somewhere in your WAN.

OR,

[root@pbltest2 dev]# cat < /dev/tcp/192.168.0.89/22
SSH-2.0-OpenSSH_4.3