premise:
mysql: A machine
Application: B-machine
I set up a cross-domain access environment and access my local mysql database on another machine, but I can't connect all the time and report a 2003 error. There is no problem with mysql authorization checks. I suddenly thought, can I ping it, A I can ping B, but B can't ping A. I looked online and said that it was a problem with the win7 firewall. Then I turned off the firewall of A, and then B pinged A again, reporting that the target host could not be found, and then I turned the firewall of B again. Closed, then the ping is smooth, and the DB connection is smooth.
Lesson: DB failure may not be the problem of mysql, let's look at the network first