How to activate or open port in CSF firewall of my VPS ?

Login into server through SSH using a Terminal or Putty.

Open the csf configuration file:

/etc/csf/csf.conf

and add the port number ,which you mean to open in server

# Allow incoming TCP ports

TCP_IN = 21,22,25,54,81,113,143,473,965,187,393,991,261

# Allow outgoing TCP ports

TCP_OUT =
21,22,25,54,81,113,143,473,965,187,393,991,261

CSF then needs to be restarted for the change to take effect:

csf -r

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