What does the error message "Error SQLSTATE[HY000] [2002] Connection refused" mean in the context of deploying Laravel 9.0?

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The error message "Error SQLSTATE[HY000] [2002] Connection refused" in the context of deploying Laravel 9.0 means that the application is unable to connect to the database due to an issue with the database configuration settings or because the database is not accessible. This error is typically caused by one of the following issues:

1. The database server is not running or not accepting connections from the application server.
2. The database server is running, but the credentials provided in the Laravel application configuration file are incorrect.
3. The firewall on either the application server or the database server is blocking the connection.
4. The database server is not configured to accept connections from the remote IP address of the application server.

To resolve this error, check the database configuration settings in the Laravel application configuration file to ensure that they are correct. Additionally, verify that the database server is running and accepting connections from the application server. It may also be necessary to check firewall settings and ensure that the database server is configured to accept connections from the application server.