# Constants
AtLeastOnce represents "acknowledged delivery" (>=1).
AtMostOnce represents "fire and forget" (<=1).
ErrBadUserNameOrPassword is "Connection Refused: bad user name or password".
ErrIdentifierRejected is "Connection Refused: identifier rejected".
ErrNotAuthorized is "Connection Refused: not authorized".
ErrServerUnavailable is "Connection Refused: server unavailable".
ErrUnacceptableProtocolVersion is "Connection Refused: unacceptable protocol version".
ExactlyOnce represents "assured delivery" (=1).
Failure indicates "subscription failed".
# Variables
DefaultAdapter is a default server adapter.
DefaultOptions is used as Server#Options for default.
ErrAlreadyServerd indicates the server is served already.
ErrDisconnected uses when the connection should be disconnected.
ErrInvalidCloudAdapter indicates Adapter#Connect() returns invalid CloudAdapter.
ErrNotAcceptable uses when adapter couldn't accept the packet.
ErrNotServing indicates the server is not under serving.
ErrNotSuported uses when adapter not implemented yet.
ErrUnknownProtocol indicates connect adddress includes unknown protocol.
ErrUnsupportedQoS uses when adapter detect unsupported QoS.
# Structs
Message represents published message.
NullAdapter is a default implementation of server adapter.
NullClientAdapter is a default implementation of client adapter.
Options represents MQTT server options.
Server is a instance of MQTT server.
Topic represents a topic filter fanned in.
# Interfaces
Adapter provides MQTT server (broker) adapter.
AdapterError represents adapter error.
Client provides interface to client connection.
ClientAdapter prorvides MQTT client adapter.
PacketFilter filters all packets which receive and send.