In fact, this function, MySQL added really too late. In MariaDB 10.0 and Percona5.6 version, there are parameters extra_port can log on "back door" to solve.
In MySQL version 8.0, there is a similar argument to achieve this functionality.
admin_address = 127.0.0.1 admin_port = 13308 create_admin_listener_thread = ON
Note: does not support dynamic changes, write dead restart mysqld process to take effect in my.cnf configuration file.
Q: Too many connections will appear under what circumstances?
A: mysqld actually allows max_connections + 1 client connections, and providing users with the SUPER privilege rights PROCESS.
Demo:
Only you need to specify
admin_port = 13308
13308 port number, you can connect up.