Package broker provides an extensible MQTT 3.1.1 broker implementation.
Get it using go's standard toolset:
$ go get github.com/gomqtt/broker// A Backend provides effective queuing functionality to a Broker and its Clients.
type Backend interface {
// Authenticate should authenticate the client using the user and password
// values and return true if the client is eligible to continue or false
// when the broker should terminate the connection.
Authenticate(client *Client, user, password string) (bool, error)
// Setup is called when a new client comes online and is successfully
// authenticated. Setup should return the already stored session for the
// supplied id or create and return a new one. If the supplied id has a zero
// length, a new temporary session should returned that is not stored
// further. The backend may also close any existing clients that use the
// same client id.
//
// Note: In this call the Backend may also allocate other resources and
// setup the client for further usage as the broker will acknowledge the
// connection when the call returns.
Setup(client *Client, id string) (Session, bool, error)
// QueueOffline is called after the clients stored subscriptions have been
// resubscribed. It should be used to trigger a background process that
// forwards all missed messages.
QueueOffline(client *Client) error
// Subscribe should subscribe the passed client to the specified topic and
// call Publish with any incoming messages.
Subscribe(client *Client, topic string) error
// Unsubscribe should unsubscribe the passed client from the specified topic.
Unsubscribe(client *Client, topic string) error
// StoreRetained should store the specified message.
StoreRetained(client *Client, msg *packet.Message) error
// ClearRetained should remove the stored messages for the given topic.
ClearRetained(client *Client, topic string) error
// QueueRetained is called after acknowledging a subscription and should be
// used to trigger a background process that forwards all retained messages.
QueueRetained(client *Client, topic string) error
// Publish should forward the passed message to all other clients that hold
// a subscription that matches the messages topic. It should also add the
// message to all sessions that have a matching offline subscription.
Publish(client *Client, msg *packet.Message) error
// Terminate is called when the client goes offline. Terminate should
// unsubscribe the passed client from all previously subscribed topics. The
// backend may also convert a clients subscriptions to offline subscriptions.
//
// Note: The Backend may also cleanup previously allocated resources for
// that client as the broker will close the connection when the call
// returns.
Terminate(client *Client) error
}
// A Session is used to persist incoming/outgoing packets, subscriptions and the
// will.
type Session interface {
// PacketID should return the next id for outgoing packets.
PacketID() uint16
// SavePacket should store a packet in the session. An eventual existing
// packet with the same id should be quietly overwritten.
SavePacket(direction string, pkt packet.Packet) error
// LookupPacket should retrieve a packet from the session using the packet id.
LookupPacket(direction string, id uint16) (packet.Packet, error)
// DeletePacket should remove a packet from the session. The method should
// not return an error if no packet with the specified id does exists.
DeletePacket(direction string, id uint16) error
// AllPackets should return all packets currently saved in the session. This
// method is used to resend stored packets when the session is resumed.
AllPackets(direction string) ([]packet.Packet, error)
// SaveSubscription should store the subscription in the session. An eventual
// subscription with the same topic should be quietly overwritten.
SaveSubscription(sub *packet.Subscription) error
// LookupSubscription should match a topic against the stored subscriptions
// and eventually return the first found subscription.
LookupSubscription(topic string) (*packet.Subscription, error)
// DeleteSubscription should remove the subscription from the session. The
// method should not return an error if no subscription with the specified
// topic does exist.
DeleteSubscription(topic string) error
// AllSubscriptions should return all subscriptions currently saved in the
// session. This method is used to restore a clients subscriptions when the
// session is resumed.
AllSubscriptions() ([]*packet.Subscription, error)
// SaveWill should store the will message.
SaveWill(msg *packet.Message) error
// LookupWill should retrieve the will message.
LookupWill() (*packet.Message, error)
// ClearWill should remove the will message from the store.
ClearWill() error
// Reset should completely reset the session.
Reset() error
}