The jar package has been launched on Alibaba cloud server and the security group has been opened, but postman still can't run. What should we do

Are there any friends who use Alibaba cloud servers , Today I met xshell It clearly shows that the server is connected ,Jar It's working , but postman The test always shows that the interface cannot be sent .

see URL, Fill in the parameters , There is no problem filling in the interface type , But it just doesn't work , Later I learned that I had to solve it like this ：

1. The problem is that there is a security group and an internal firewall, which is unnecessary ！！！

2. hold Alibaba Linux Your firewall is off ！！

3.Ali The server should be configured iptable Firewall ！！！

4. Try the following commands one by one, and I'll solve it ：

        ① service iptables status    Check the firewall status for problems

        ② service iptables stop      Turn off firewall

        ③ firewall-cmd --state     Check the status ,//running Said to run

        ④ systemctl stop firewalld.service     Turn off firewall