How do I tell if a TCP network port is open or not?
A TCP/IP network connection may be either blocked, dropped, open, or filtered. These actions are generally controlled by the IPtables firewall the system uses and is independent of any process or program that may be listening on a network port.
Checking to see if a port is open, blocked, dropped, or filtered at the firewall is not simple. There are two ways to do this - test the port ex...
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