The corresponding port is automatically enabled when the firewall is enabled in Linux.

Article Title: The corresponding port is automatically enabled when the firewall is enabled in Linux. Linux is a technology channel of the IT lab in China. Including desktop applications, Linux system management, kernel research, embedded systems, open source, and other basic categories. When Linux opens a firewall, you will find that it is okay to log on to port 23 from the local machine, however, if you log on to the linux system from another pc, you will find the following error:

The connection to the host cannot be opened. In port 23, the connection fails.

Because the linux Firewall disables port 23 by default. If remote logon is allowed, you can disable the firewall or open the firewall to open port 23, as shown below:

Takes effect immediately and becomes invalid after restart

Enable: service iptables start

Disable: service iptables stop

Effective after restart

Enable: chkconfig iptables on

Close: chkconfig iptables off

When the firewall is enabled, make the following settings to enable the relevant port

Modify the/etc/sysconfig/iptables file and add the following content:

-A RH-Firewall-1-INPUT-m state -- state NEW-m tcp-p tcp -- dport 23-j ACCEPT