Problem like this can happen if MySQL is not running. You should check it’s status by using systemctl command:

sudo systemctl status mysql

If you are using Ubuntu 14.04, above command will not work and you’ll have to use:

sudo service mysql status

If you see that it’s stopped or failed try to start it again to see will it come up:

sudo systemctl start mysql

Or using service command:

sudo service mysql start

Check status once again. If it’s running, try accessing it. In that case you need to analyze logs to see why it went down.
If not, did you change something in MySQL configuration? If yes, revisit it and make sure you didn’t make any mistake.

If starting service worked, to prevent this happening, you have to check log files.
Usual reason why MySQL goes down is that it went out-of-memory.
Take a look at system log - syslog:

sudo nano /var/log/syslog

If you find there any OOM, out of memory, OOM killer entries that means MySQL went down due to out-of-memory. In that case consider upgrading Droplet or installing Swap.
If not, look around and see is there any other MySQL error.

@nritsonsa478bff2e7b215cb05

How was MySQL installed and did you modify any configuration files (i.e. my.cnf) at any point?

This is a really common error when it comes to modifying configuration as some configuration works on one version but not another. Knowing which works where is the often the difference between a working and failing MySQL server.

If you didn’t modify any configuration, I would recommend first simply restarting your Droplet. Seems very basic, but sometimes that’s all that’s needed without getting overly complicated and performing too many steps (i.e. prevent overkill).

You can do this from the command line by running:

shutdown -r now

Which simply means shutdown, restart, now! The server will disconnect and within a minute or so should be back online.

status says its active (running)
the log says : http://prntscr.com/dx3l1h

UFW is blocking the port?