How to troubleshoot a failed connection to an external database in Docker?

When connecting to an external database using Docker, there are several common issues that may cause the connection to fail. You can try the following solutions:

1. Ensure that the database server is running: Make sure that the external database server you want to connect to is already running and has opened the relevant ports.
2. Check the connection string: Ensure that the connection string used to connect to the database is correct, and make sure that information such as username, password, and database name are accurate.
3. Check network connectivity: Make sure your Docker container and database server are on the same network and the network connection is working properly. You can try pinging the IP address of the database server from the Docker container to check if the network connection is functioning correctly.
4. Check firewall settings: If the host where your database server is located has a firewall enabled, make sure you have allowed database connection requests from Docker containers.
5. Check database permissions: Make sure the database user you are using has sufficient permissions to connect to the database. You can try connecting to the database with the root user, or check if the user you want to use has permission to connect.
6. Check the database configuration: Review the database server’s configuration file to ensure remote connections are permitted, and that the correct IP address and port have been configured.

If none of the above methods work, you can try troubleshooting the issue by running the following commands inside the Docker container.

1. Check if the IP address and port of the database server can be accessed using the telnet command: telnet
2. Check the network connection status using the ping command: ping .

If the issue persists, you can ask for help in relevant forums or communities, or consult related documents and tutorials for more assistance.