0             8             16
+---------------------------+
|Protocol name length = 4   |
+---------------------------+
|     'M'            'Q'    |
+---------------------------+
|     'T'            'T'    |
+---------------------------+
|Proto.level=5|Connect flags|          
+---------------------------+
|        Keep alive         |
+---------------------------+
|        Payload            | 
|  Client Identifier        |
|  (UTF-8-encoded string)   |
| User Name as access token |
|   (UTF-8-encoded string)  |
| Password for signature/MAC|
|     (Binary Data)         |
+---------------------------+