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Version: 1.0

Firewall and Security Group

About Firewall​

In Linux, the firewall exists as a daemon process, the name of the service is firewalld , which can define a set of rules to control the network access of the external incoming system.

Security Group Settings​

However, in order to simplify the security use, the cloud platform achieves the same function as the firewall through a visual management interface-security group.

Therefore, when using a cloud server, the firewall will be turned off and replaced with a security group.

FAQ​

How to test the port is enabled?​

You can use nc or telnet to test it:

  • Use nc

    # Success
    $ nc -zvw10 8.142.3.195 22
    Connection to 8.142.3.195 22 port [tcp/*] succeeded!

    # Failed
    $ nc -zvw10 8.142.3.195 9091
    nc: connect to 8.142.3.195 port 9093 (tcp) failed: Connection refused

  • Use telnet

    # Success
    $ telnet 8.142.3.195 22
    Trying 8.142.3.195...
    Connected to 8.142.3.195.
    Escape character is '^]'.

    # Failed
    $ telnet 8.142.3.195 9091
    Trying 8.142.3.195...
    telnet: Unable to connect to remote host: Connection refused