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@@ -31,28 +31,22 @@ Design Philosophy
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System Layers
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-------------
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-1. Connection Layer:
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+1. Connection Layer
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Handle TCP and WebSocket connections, encode/decode MQTT packets.
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-2. Session Layer:
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+2. Session Layer
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Process MQTT PUBLISH/SUBSCRIBE Packets received from client, and deliver MQTT messages to client.
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-3. PubSub Layer:
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+3. PubSub Layer
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Dispatch MQTT messages to subscribers in a node.
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-
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-4. Routing(Distributed) Layer:
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+
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+4. Routing(Distributed) Layer
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Route MQTT messages between clustered nodes.
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-.. code::
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-
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- -------------- ----------- ---------- ----------
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- Client --> | Connection | --> | Session | --> | PubSub | --> | Router |
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- -------------- ----------- ---------- ----------
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-
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----------------
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Connection Layer
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----------------
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@@ -132,13 +126,12 @@ PacketId and MessageId
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The 16bits PacketId is defined by MQTT Protocol Specification, used by client/server to PUBLISH/PUBACK packets. A GUID(128bits globally unique Id) will be generated by the broker and assigned to a MQTT message.
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-Format of the globally unique message id:
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+Format of the globally unique message id::
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-+------------------------+----------------+------------+
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-| Timestamp | NodeID + PID | Sequence |
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-+------------------------+----------------+------------+
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-| <-------64bits-------> | <---48bits---> | <-16bits-> |
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-+------------------------+----------------+------------+
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+ --------------------------------------------------------
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+ | Timestamp | NodeID + PID | Sequence |
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+ |<------- 64bits ------->|<--- 48bits --->|<- 16bits ->|
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+ --------------------------------------------------------
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1. Timestamp: erlang:system_time if Erlang >= R18, otherwise os:timestamp
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2. NodeId: encode node() to 2 bytes integer
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Feng