About CentOS7 can ping but Telnet is unable to connect to the upper port

Yesterday, at the request of the students in their company's cloud platform to find a cloud host deployed Distributed File System Fastdfs,
The installation went smoothly, but there was a problem when starting the service, and the tracker tracker very easily started up, end
The mouth can also be seen through the ss-ntl, but in the boot memory storage, but how can not find the corresponding port, check
Looked at the log, found that storage can not connect to the tracker, after determining that the configuration does not have a problem, think that may be
Cloud host problem, sure enough, a test found cloud host port can not telnet pass, on the Internet to check some of the data collated as follows: 1, may be the port does not get up, this does not apply to me, because Ss-ntl can clearly see tracker port has been started
Up, so this is ruled out. 2, firewall does not shut down, CentOS 7 of the firewall default is firewall rather than the previous iptables, so need to determine
Whether the firewall is turned off, and if iptables is not installed, you only need to pass Systemctl stop Firewalld.service
and systemctl disable Firewalld.service shutdown, the former is a shutdown of the firewall firewall, the latter is no boot boot,
The firewall status can then be viewed via firewall-cmd–state (Turn off display notrunning, turn on display running).
You can use Systemctl stop iptables.service to turn off the iptables firewall. Here I put the firewall off, but,
But it's not going to work. Found the port is still telnet. 3, finally I suddenly remembered, I am using the cloud host, is not a common virtual machine, so the port can not access in addition to the above
Factor control, there are security group controls on the cloud platform, and sure enough, the cloud host bound security group does not open this end
Port, after the downlink permission to join the security group, it was successful, storage also started.

If your host is also a cloud host, be sure to determine whether your security group is open, whether the port has the right to downlink, otherwise
Configuration is no use.