Troubleshooting Common MySQL Connection Errors
Jul 05, 2025 am 01:24 AMWhen encountering MySQL connection problems, 1. First confirm whether the user name and password are correct, and check whether there are spelling errors or permission restrictions; 2. Make sure the MySQL service is running normally, restart the service and view the logs if necessary; 3. Verify that the network is unobstructed, ensure that the port is open and there is no firewall block; 4. Check the binding address, connection limit and SSL settings in the MySQL configuration file to ensure that the configuration allows external connections.
MySQL connection problems are common in development and operation and maintenance, especially when services are just deployed or databases are migrated. When you encounter a situation where you cannot connect to the database, don’t rush to check the log stack. Start by checking a few common points, which can often quickly locate problems.

1. Check whether the username and password are correct
This is one of the most common sources of errors. If you prompt Access denied for user 'xxx'@'yyy'
when connecting MySQL, it means that the authentication failed.

- Confirm whether the username and password are spelled incorrectly (especially uppercase and uppercase and special characters)
- If configuration files or environment variables are used, check whether the values ??in these places are overwritten.
- If it is a remote connection, confirm whether the user has permission to connect from the current IP (see the
Host
field in themysql.user
table)
Sometimes, even if the password is correct, a user does not authorize access to a specific database, a similar error will occur. You can check user permissions with the following command:
SHOW GRANTS FOR 'your_user'@'your_host';
2. Check whether MySQL is running normally
Sometimes the connection failure is not because of the account problem, but because the MySQL service has not started at all.

- Execute
systemctl status mysql
orservice mysql status
to view status - If it is not running, try restarting:
systemctl start mysql
- Check if there is any error message in MySQL log (usually in
/var/log/mysql/error.log
or similar path)
If you are connecting to MySQL on a remote server from locally, make sure that MySQL listens for the corresponding port (default 3306) and allows external access.
3. Check whether the network connection is open
When connecting to MySQL remotely, network problems are the second most common cause.
- Use
ping
to test whether the server is reachable - Use
telnet your.mysql.server 3306
ornc -zv your.mysql.server 3306
to check whether the port is open - If there are firewall or security group rules, make sure port 3306 is open to your IP
Some cloud service providers only allow local connections by default, and require manual configuration of whitelists or security group policies.
4. Check if MySQL configuration restricts connections
MySQL itself can also control connection behavior through configuration files.
- Open
my.cnf
ormy.ini
and find out whetherbind-address
is bound to 127.0.0.1 - so that you can only connect locally - Check whether the
max_connections
setting is too small, resulting in the new connection being rejected after the number of connections is full. - If SSL authentication connection is enabled, the client must also configure the corresponding SSL parameters.
In addition, if you use a connection pool (such as in Java or Node.js), be careful whether the connection pool settings are reasonable to avoid connection leakage or timeout.
Basically, these common connection problems and solutions. Although there are many error messages in MySQL, most of them can find clues from these aspects. What is not complicated but easy to ignore is the mutual influence between configuration items and network details, especially when accessing across servers.
The above is the detailed content of Troubleshooting Common MySQL Connection Errors. For more information, please follow other related articles on the PHP Chinese website!

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