Multi-language extension-protocol access

The scalability brought by this function to EMQX is very powerful. It can process any proprietary protocol in a programming language familiar to users, and enjoy the advantages of extremely high concurrent connections brought by the EMQX system.

-Very strong expansion capability. Use gRPC as the RPC communication framework to support various mainstream programming languages -Fully asynchronous IO. The connection layer is implemented in a completely asynchronous non-blocking I/O way -The connection layer is transparent. Fully support TCP\TLS UDP\DTLS connection management, and provide a unified API for the upper layer -Connection management capabilities. For example, the maximum number of connections, rate limits for connections and throughput, IP blacklists, etc.

The main contents of this module include:

1. Connection layer: This part mainly maintains the life cycle of Socket, and the sending and receiving of data. Its functional requirements include:

   -Listen to a port. When a new TCP/UDP connection arrives, a connection process is started to maintain the connection status. -Call the ʻOnSocketCreated callback. Used to notify the external module that the connection is closed. -Call the ʻOnReceivedBytescallback. Used to notify the external module ** the newly received data packet for this connection**. -ProvideSendinterface. Called by external modules, **used to send data packets**. -ProvideClose` interface. Called by external modules, used to actively close the connection.

2. Protocol/session layer: This part mainly provides PUB/SUB interface** to realize message intercommunication with the EMQX Broker system. include:

   -Provide ʻAuthenticateinterface. Used by external modules to register clients to the cluster. -ProvideStartTimerinterface. Called by external modules to start timers such as heartbeat for the connection process. -ProvidePublishinterface. Used by external modules to publish messages in EMQX Broker. -Provide theSubscribe interface. Called by external modules to unsubscribe a topic. -Call the ʻOnTimerTimeoutcallback. It is used to handle events that the timer expires. -Call the ʻOnReceivedMessages callback. Used to receive downlink messages (after subscribing to the topic successfully, if there is a message on the topic, this method will be called back)

For details, see: , for example, the definition of the interface is:

Before using this module, users need to develop and deploy a gRPC service and implement the interface defined by ʻexproto.proto`.

The steps are as follows:

1. Copy the current version of lib/emqx_exproto-<x.y.z>/priv/protos/exproto.proto file.
2. Use the gRPC framework of the corresponding programming language to generate the gRPC server code of ʻexproto.proto`.

After the development is completed, the service needs to be deployed to a server that can communicate with EMQX, and the port is open.

The gRPC framework of each language can be referred to:

After successfully deploying the gRPC service, you can open the multi-language extension protocol access module through the dashboard page, and configure the following three parts to use it successfully:

1. The listening address of ExProto’s service. Used to receive gRPC requests.
2. Configure Listener (Listener) to provide TCP/UDP/SSL/DTLS address monitoring. Used to monitor and receive device connections.
3. Specify a service address of ConnectionHandler for each listener. A service used to send various event callbacks to users.

Open , click the “Modules” tab on the left, and choose to add:

Select “Multilingual Extended Protocol Access”:

Configure the listening address of the ConnectionAdapter service, and whether to enable SSL listening for it:

Click “Add Listener” to configure the listener for the ExProto module, including:

1. The listener’s listening address and listening type, which indicate how to receive the Socket connection of the custom protocol.

Click OK to complete the listener addition; click Add to complete the creation of the module: