The error should be looking as below:
You have an unresolved error when starting csf:
Error: Error processing command for line  (6 times): [Another app is currently holding the xtables lock. Perhaps you want to use the -w option?], at line 339 in /usr/sbin/csf
You need to restart csf successfully to remove this warning, or delete /etc/csf/csf.error… Read the rest
Iptables is default linux firewall used to set up, maintain, and inspect the tables of IPv4 packet filter rules in the Linux kernel. Several different tables may be defined. Each table contains a number of built-in chains and may also contain user-defined chains.… Read the rest
The following commands will allow you to open tcp or udp ports on the server.
Before using commands for opening the port please make ensure the specific port is already opend and what is the use of that port.… Read the rest