Troubleshooting of service port failure

Solutions

1、 Use netstat -nplt View on port tcp, still tcp6
2、 Check to see if it is only bound to ipv6 On sysctl net.ipv6.bindv6only
3、 see ipv4 Data can be forwarded on ：sysctl net.ipv4.ip_forward
4、 Check whether the firewall disables ports

One 、 Check the port

[[email protected] ~]# netstat -tnlp |grep 80
tcp        0      0 192.168.180.45:2379     0.0.0.0:*               LISTEN      17092/etcd
tcp        0      0 192.168.180.45:2380     0.0.0.0:*               LISTEN      17092/etcd
tcp6       0      0 :::20080                :::*                    LISTEN      11937/docker-proxy
tcp6       0      0 :::1080                 :::*                    LISTEN      13449/docker-proxy

It can be seen that 20080 Ports only appear in tcp6 On .

Two 、 see ipv6

[[email protected] ~]# sysctl net.ipv6.bindv6only
net.ipv6.bindv6only = 0

0 It means that it is not only bound to ipv6 On

If you want to solve it ：

vim /etc/sysctl.conf

# Add the following line 
net.ipv6.bindv6only=1

# Then save to exit .  Restart the network 
systemctl restart network

3、 ... and 、 see ipv4 Forwarding status

[[email protected] ~]# sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 1

1 Indicates that you can forward , in other words tcp6 The data on the can also pass tcp forward

If it is 0, solve

vi /etc/sysctl.conf

# Add the following line 
net.ipv4.ip_forward=1

# Then save to exit .  Restart the network 
5. Reload sysctl Configure or restart the network 
sysctl -p
#or
systemctl restart network

Four 、 A firewall

firewall-cmd --zone=public --add-port=20080/tcp --permanent    # allow tcp Of 3306 Port to public Area .

reference ：
centos7 A firewall （firewalld、iptables）