I did it myself because I used bind-address=127.0.0.1 to bind the local address in my /etc/mysql/my.cnf file. Just comment out this sentence and it will be fine

Turn off the Linux firewall function, or set up to allow the 3306 port of the TCP protocol to pass

http://blog.libnav.com/sql/60.html
http://www.2cto.com/os/201203/124332.html

It’s no problem to connect to mysql using the command line on the virtual machine

Local link The local service uses NETBIOS analysis, of course it can be connected

Error when using navicat connection on Windows 7:

Then, there are many reasons for this.
1. Ping Ubuntu’s address to see if it can be reached? If not, check how the network settings of your virtual machine are set up. Then check whether the ubuntu firewall is turned off.
2. Ping is successful, but Mysql still cannot connect, check your Mysql authorization. Mysql's authorization for the account includes "user name" + "source address"

I also encountered this problem. It didn’t work even after reinstalling the system. I just installed the software. What are the connection steps?

How to use Navicat for Mysql to connect to the mysql server on the Ubuntu virtual machine - SegmentFault
http://segmentfault.com/q/1010000002648801

bind-address=127.0.0.1 is preceded by # and is authorized.