To disable/enable the Linux firewall use the following command:

system-config-securitylevel-tui

CentOS 6

system-config-firewall-tui

If the package is not installed you can install it by using the following yum command.

yum install system-config-securitylevel-tui

CentOS 7

systemctl stop firewalld
systemctl disable firewalld

To disable selinux on CentOS 6 and 7 which is not displayed in the above mentioned TUI edit
/etc/selinux/config

SELINUX=disabled

or

sed -i s/SELINUX=enforcing/SELINUX=disabled/g /etc/selinux/config