How Linux opens ports

Example:

The steps to open port 10000 are as follows:

1, modify the/etc/sysconfig/iptables file, add the following line:

-A rh-firewall-1-input-m state--state new-m tcp-p TCP--dport 10000-j ACCEPT

Restart Iptables

Service Iptables Restart
　
2, restart the firewall, there are two ways to restart the firewall a) restart after the effective
Open: Chkconfig iptables on
OFF: chkconfig iptables off B) immediate effect, fail after reboot
Open: Service iptables start

Close: Service iptables stop

3, or with Menu-system-administration-firewall

To add the port that the user needs.

By the To:

A. NETSTAT-TANP to display the port status.

/usr/sbin/lsof-i

B. telnet ipaddr port

To check if the IP and port is available before making connection.

How Linux opens ports