java.net.SocketTimeoutException: Read timed out under Tomcat

A java.net.SocketTimeoutException: Read timed out error can occur when a connection to a server is blocked by a firewall or if the server is experiencing high load and is unable to process requests in a timely manner.

To troubleshoot this error when running under Tomcat, you can try the following steps:

1. Check the Tomcat logs (typically logs/catalina.out) for any errors or warnings that may indicate the cause of the timeout.
2. Check the network configuration of your Tomcat server to ensure that it is not being blocked by a firewall or network security device.
3. Check the server load and resource utilization to ensure that the server has sufficient resources to handle incoming requests.
4. If the problem persists, you may need to increase the socket read timeout setting in your Tomcat configuration. To do this, edit the soTimeout attribute in the Connector element of the server.xml file (typically for the HTTP/HTTPS connector on port 8080/8443). For example:

<Connector soTimeout="60000" ... />

This sets the socket read timeout to 60,000 milliseconds (60 seconds). Note that connectionTimeout controls TCP connection establishment, while soTimeout controls how long Tomcat waits for incoming data. Adjust the value as needed, then restart Tomcat for the changes to take effect.

5. Keep in mind that this exception is often thrown by the client, not the server. If Tomcat is responding normally, check your application's HTTP client configuration (e.g., Apache HttpClient, OkHttp, or HttpURLConnection) and ensure its read timeout is set appropriately.

I hope this helps! Let me know if you have any questions.