Mysql Workbench connection impossible to mysql server (no replies)

Hi,
I have a mysql server with user 'root' and no password.
When I do mysql -u root -p in a terminal I can connect to my server.
When I use mysql workbench, if I test this connection, it s successful,
but when I try to connect to the server I am getting this error :

Your connection attempt failed for user 'root' from your host to server at 127.0.0.1:3306: Could not open database

Please: 1 Check that mysql is running on server 127.0.0.1
2 Check that mysql is running on port 3306 (note: 3306 is the default, but this can be changed)
3 Check the root has rights to connect to 127.0.0.1 from your address (mysql rights define what clients can connect to the server and from which machines)
4 Make sure you are both providing a password if needed and using the correct password for 127.0.0.1 connecting from the host address you're connecting from

Mysql status :

Connection id: 7
Current database:
Current user: root@localhost
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 5.6.28-0ubuntu0.15.10.1 (Ubuntu)
Protocol version: 10
Connection: localhost via TCP/IP
Server characterset: latin1
Db characterset: latin1
Client characterset: utf8
Conn. characterset: utf8
TCP port: 3306
Uptime: 50 sec

Threads: 3 Questions: 69 Slow queries: 0 Opens: 67 Flush tables: 1 Open tables: 60 Queries per second avg: 1.380

If anyone has any idea of what's going wrong...
I am using ubuntu 15.10, it used to work with ubuntu 14.10 and mysql 5.5.40.
thank you.