Linux cannot be accessed by external hosts

Cause:

Firewall problem

Solution:

Method 1: Turn off the firewall

[root@localhost ~]# service iptables stop　　　　　　　　 #关闭防火墙
[root@localhost ~]# service iptables start　　　　　　　　 #开启防火墙
[root@localhost ~]# service iptables status　　　　　　　  #查看防火墙状态

The command to operate the firewall in cenOS7 or Red Hat7 has changed. The command is as follows:

[root@localhost ~]# systemctl stop firewalld.service             #关闭防火墙
[root@localhost ~]# systemctl start firewalld.service             #开启防火墙
[root@localhost ~]# systemctl status firewalld.service          #查看防火墙状态

Method 2: Open the specified port

[root@localhost ~]# vim /etc/sysconfig/iptables
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0] 
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT 
-A INPUT -p icmp -j ACCEPT 
-A INPUT -i lo -j ACCEPT 
-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT  
-A INPUT -m state --state NEW -m tcp -p tcp --dport 8080 -j ACCEPT  
-A INPUT -j REJECT --reject-with icmp-host-prohibited 
-A FORWARD -j REJECT --reject-with icmp-host-prohibited

Note: Find the line -A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT and add ## after this line #-A INPUT -m state --state NEW -m tcp -p tcp --dport 8080 -j ACCEPT , you can open the 8080 port

[root@localhost ~]# service iptables restart　　　　　　#重启防火墙才能生效

[root@localhost ~]# firewall-cmd --zone=public --add-port=8080/tcp --permanentsuccess
[root@localhost ~# firewall-cmd --reload　　　　　　　　　　#开放端口只需需要重启防火墙才能生效success

Remarks:Open port command explanation

-zone Scope

-add-port=8080/ tcp Add a port, the format is: port/communication protocol

--permanent Permanently effective

linux tutorial

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