Fail to Access only on Workbench (6.3.6 Build 517 CE(64 bits) Community)

[roberto gumucio]

I apologise.. I know this question has been asked many times before, but I've tried lots of suggestions, and simply can't find a solution.

The problem is when I try to connect on Workbench, I get the error: "Failed to Connect to MySQL at 127.0.0.1:3306 with user root"

But if I run "shell> mysqladmin version", I get:
mysqladmin Ver 8.42 Distrib 5.7.19, for Linux on x86_64
Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Server version 5.7.19
Protocol version 10
Connection Localhost via UNIX socket
UNIX socket /var/run/mysqld/mysqld.sock
Uptime: 32 sec

Threads: 1 Questions: 3 Slow queries: 0 Opens: 107 Flush tables: 1 Open tables: 26 Queries per second avg: 0.093

Also the following commands runs fine:
"shell> mysqld" (service is running)
"shell> mysql" (login on Server)

The settings of "newConnection" on WB are:
Connection Method: Standard (TCP/IP)
Parameters.Hostname: 127.0.0.1 - Port: 3306
Parameters.Username: root
... (next values are by Default)

My System is Ubuntu 14.04 LTS

Thanks in advance.