Firewall and Security Group
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.
- Azure Security Group
- AWS Security Group
- Alibaba Cloud Security Group
- Tencent Cloud Security Group
- HUAWEI Cloud Security Group
How to test the port is enabled?
You can use nc or telnet to test it:
$ nc -zvw10 126.96.36.199 22
Connection to 188.8.131.52 22 port [tcp/*] succeeded!
$ nc -zvw10 184.108.40.206 9091
nc: connect to 220.127.116.11 port 9093 (tcp) failed: Connection refused
$ telnet 18.104.22.168 22
Connected to 22.214.171.124.
Escape character is '^]'.
$ telnet 126.96.36.199 9091
telnet: Unable to connect to remote host: Connection refused