Alibaba Cloud Server Tomcat cannot be accessed

1. Introduction

I have configured Tomcat on Alibaba Cloud before, and it was accessible after testing. Later, I uninstalled Tomcat for some reasons. I started to reinstall Tomcat and start testing last night, but found that it was still inaccessible. Then I wasted another night. The main reasons may be the following. I hope it can help you.

2. Solution

Alibaba Cloud has two layers of inspection measures. The first layer is the firewall, and the second layer is the security group. Here we first configure the firewall

2.1 Configure the firewall and open the port

Here we first check whether the firewall status is turned on

systemctl status firewalld
``
If this error `Unit firewalld.service could not be found.` appears, it means that we do not have the firewall service, and we need to download the firewall first;

```java
yum install firewalld firewall-config

After the download is complete, we need to start the firewall first:

service firewalld start

After the startup is complete, we open Tomcat's port 8080

firewall-cmd --zone=public --permanent --add-port=8080/tcp

After opening the port, we need to refresh the effect, which can be achieved by the following command:

firewall-cmd --reload

After refreshing, we can check the opened port number through the following command:

firewall-cmd --list-all

If you see the following interface, it means that the firewall has opened the following ports

2.2 Configure security groups in the Alibaba Cloud console

It should be noted here that it is best to configure both the inbound and outbound directions of port 8080, so that the security group has also been configured.

2.3 Check ports and resolve port conflicts

At this time, we start Tomcat. Here we enter the bin directory of Tomcat and start Tomcat through the following command

./startup.sh

It is best not to use the sh startup.sh command to start Tomcat
At this time, if your ports do not conflict, then you can visit阿里云ip:8080 , and you should be able to see the Tomcat page, but if you don't see it, it basically means that there is a port conflict. At this time, we need to check the port to see which port is conflicting. At this time, we need to check the log, usually in this path

Enter and view through vi 日志名,
Seeing errors similar to this

org.apache.catalina.core.StandardServer.await StandardServer.await: create[localhost:8106]:

This means that the port has conflicted and needs to be modified. Then we need to go to conf/server.xml to modify and find the corresponding port number.

There are mainly several places where port numbers may conflict:

Modify the port according to your actual situation. Start Tomcat every time you modify it. If there is no port error, it means that Tomcat can start normally.

Just like that, my lovely Tom cat finally came out, thank God.

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