MySQL Port Numbers

MySQL, one of the world's most popular open-source relational database management systems, communicates over a network using a standardized port. If you're configuring MySQL, setting up firewall rules, or debugging network-related issues, it's essential to understand which ports MySQL uses. In this guide, we'll dive into the default MySQL port number and discuss related port considerations.

Default MySQL Port

By default, MySQL uses port 3306 for client-server communication. When you install MySQL without any specific configurations regarding its port number, clients will try to connect to the server on port 3306.

mysql -h hostname -P 3306 -u username -p

Secure Socket Layer (SSL)

MySQL can also use SSL for encrypted connections. When you configure MySQL to use SSL, it still uses port 3306 by default. The port number doesn't change; instead, the data transmitted over the port is encrypted.

Changing the Default Port

While the default port is 3306, you can configure MySQL to listen on a different port. To do this:

1. Open the MySQL configuration file, typically named my.cnf or my.ini.
2. Locate the port directive under the [mysqld] section.

[mysqld]
port = 3307

1. Change the port value (e.g., to 3307).
2. Save the file and restart the MySQL server.

Why Change the Default Port?

1. Security Through Obscurity: While not a replacement for proper security measures, changing the default port can prevent automated scans from identifying an active MySQL service easily.
2. Running Multiple Instances: If you're running multiple MySQL server instances on the same machine, each must have a unique port.
3. Port Conflicts: Another application may already be using port 3306, necessitating a change.

Other Relevant Ports

• MySQLX Plugin: If you use the X Plugin for MySQL, it listens for connections on port 33060 by default.
• Cluster & Replication: MySQL Cluster and replication setups might use other ports for communication between nodes or between master and slave instances. Ensure you review the specific documentation for your setup.

Checking the Active MySQL Port

If you need to confirm which port your MySQL server is listening on:

From the MySQL prompt:

SHOW GLOBAL VARIABLES LIKE 'port';

From the command line, using netstat:

netstat -tuln | grep mysqld

Firewall Considerations

If you're running a firewall (e.g., iptables or ufw), ensure that you allow connections to the MySQL port. For example, with ufw:

sudo ufw allow 3306/tcp

Replace 3306 with your configured port if different.

Closing Thoughts

Understanding MySQL's port numbers and their configurations is essential for proper setup, maintenance, and security of your MySQL environment. Always ensure that any opened port is secured and monitored, irrespective of its number. Remember, while changing the default port can be part of your security strategy, it should never be the only strategy.