Syntax Error in Parameters
The command syntax was valid but the parameters or arguments supplied were syntactically incorrect.
501
501
Not Implemented
The server does not support the functionality required to fulfil the request.
frame-error
The broker received a malformed frame, for example one with an incorrect frame type or a frame boundary that does not align with the expected structure. This is a hard error and the connection is closed.
Not Implemented
The server does not support the functionality required to fulfil the request. The server does not recognise the request method and cannot support it for any user.
Syntax error in parameters
The command was recognised but its arguments are syntactically incorrect.