We patiently check in order, generally there are the following reasons, which are quite simple

1、 It may be that the agent host cannot ping the server host, or cannot access the server port.

If the following error message appears in the agent log file (in the agent/log directory), it means that the agent host cannot ping the server host and the network is disconnected.

......
[wgcloud-agent]2024/12/02 10:44:21 WgcloudAgent.go:89: submit server begin
[wgcloud-agent]2024/12/02 10:44:23 WgcloudAgent.go:93: Host monitoring information reporting server error: Post "http://192.168.1.2:9999/agentGo/minTask": dial tcp 192.168.1.2:9999: connectex: No connection could be made because the target machine actively refused it.
[wgcloud-agent]2024/12/02 10:44:23 WgcloudAgent.go:56: runtime error: invalid memory address or nil pointer dereference
[wgcloud-agent]2024/12/02 10:44:25 WgcloudAgent.go:152: Host monitoring Ext information reporting server error: Post "http://192.168.1.2:9999/agentGo/minTaskHostExt": dial tcp 192.168.1.2:9999: connectex: No connection could be made because the target machine actively refused it.
[wgcloud-agent]2024/12/02 10:44:25 WgcloudAgent.go:111: runtime error: invalid memory address or nil pointer dereference
......

We can use the command ping [server host IP] on the agent host to test network connectivity.

If the following error message appears in the agent log file, it means that the agent host telnet cannot reach the server port, the network connection times out, and the firewall may not open the port.

......
[wgcloud-agent]2024/12/02 10:48:05 WgcloudAgent.go:89: submit server begin
[wgcloud-agent]2024/12/02 10:48:25 WgcloudAgent.go:93: Host monitoring information reporting server error: Post "http://192.168.1.2:9999/agentGo/minTask": context deadline exceeded (Client.Timeout exceeded while awaiting headers)
[wgcloud-agent]2024/12/02 10:48:25 WgcloudAgent.go:56: runtime error: invalid memory address or nil pointer dereference
[wgcloud-agent]2024/12/02 10:48:45 WgcloudAgent.go:152: Host monitoring Ext information reporting server error: Post "http://192.168.1.2:9999/agentGo/minTaskHostExt": context deadline exceeded (Client.Timeout exceeded while awaiting headers)
[wgcloud-agent]2024/12/02 10:48:45 WgcloudAgent.go:111: runtime error: invalid memory address or nil pointer dereference
......

We can use the command telnet [server host IP] 9999 on the agent host to test network connectivity.

2、 Check the serverUrl of the agent configuration file

Perhaps there is a problem with the character format, such as commas and colons being written as Chinese characters, or it could be an error in IP or port writing

3、 The time difference between the server and agent's host systems cannot exceed 16 hours

If the time difference does not exceed 16 hours, print a message similar to 'Anti tampering Verification Error' and ignore it. There will be no impact

4、Is it because the agent's process wgcloud-agent was killed, or the agent host was restarted or powered off, causing the agent to not run

We just need to start the agent again

Agent process inexplicably stopped running by kill, how to handle it

5、 wgcloud-server-release.jar Do not edit or modify

Do not change the file name either. If you have edited it, please restore it to the original wgcloud-server-release.jar in the installation package

6、 The server and agent should maintain the same version number

How to check the version numbers of servers and agents

7、Do not close the server-side daemon (wgcloud-daemon-release)

Especially on Windows, do not close the daemon window. If it's Linux, the daemon may have been killed. Check if the daemon is still alive （ps -ef | grep wgcloud）

Another possibility is that the server or agent is deployed on Windows, and you accidentally left-clicked the black window where the program was running, entering the [Select] mode. Right-click to restore, as shown below

If it is caused by this reason, simply restart the server (the daemon will start with the server), and all controlled agents will gradually resume online within 1 hour. You can also manually restart the agents (go online immediately)

8、 The default port of the daemon wgcloud daemon release was modified, but the daemon port was not synchronously modified in the server configuration file

View modification instructions

9、Check if the local server can be accessed normally http://localhost:9997 Obtain return value

For example: 2faa233a1400201bedc199fe1d8ab393，If the localhost of the server host cannot be used, you can change the localhost in the configuration file server/config/application.yml to the server host IP in the following configuration items

Note that if changed to IP, check if there is a firewall blocking port 9997

10、Check the server logs to see if the server is unable to connect to the database

If this is the case, after handling the server, the agent will gradually go online within 1 hour, or you can restart the agent to go online immediately

11、If the server is running on a CPU architecture system such as ARM or MIPS, the daemon wgcloud-daemon-release needs to be replaced with the corresponding version

Click to download

12、If the server or daemon (wgcloud-daemon-release) does not start and run for a long time

So when the server restarts, the agent will automatically resume online within 1 hour without restarting the agent. You can also manually restart the agent and it will immediately resume online

13、Check if there is security software and set some filtering rules, which prevent the agent from reporting data to the server

Some firewalls have strange rules that allow agents to request data from the server, but cannot submit or report data to the server

14、If deploying a server on Docker

Let's check if we have changed the localhost in the daemon URL in config/application.yml to the host IP address, as follows

Generally, it needs to be modified unless it is accessible within the Docker container http://localhost:9997 If so, then it can be left unchanged

15、Generally, these are the reasons mentioned above