Linux system to open the Firewall automatically opens the corresponding port

When Linux open behind a firewall, you'll find, from the native login 23 port is no problem, but if from another PC to log in to the linux system, you will find tips for this error: cannot open a connection to host, on port 23: Connect failed because the linux Firewall is turned off by default, if 23 port to allow remote login, you can turn off the firewall, or you can open the firewall open port 23 as follows: with immediate effect, restart after failure in opening: serviceiptablesstart close: serviceiptablesstop restart after opening: chkconfigiptableson close: chkconfigiptablesof in opening up a firewall, make the following settings, open the relevant ports modify/etc/sysconfig/iptables file, add the following:-ARH-Firewall-1-INPUT-mstate — stateNEW-mtcp-ptcp — dport23-jACCEPT