基於Pub/Sub模式的阿里雲IoT同步呼叫詳解

wongxmig發表於2018-09-12
模式阿里

1.同步呼叫場景

1.1 背景

MQTT協議是基於PUB/SUB的非同步通訊模式，無法實現服務端下發指令給裝置端，同時需要裝置端返回響應結果的場景。
IoT物聯網平臺基於MQTT協議制定了一套請求和響應的同步機制，無需改動MQTT協議即可實現同步通訊。應用伺服器通過POP API發起Rrpc呼叫，IoT裝置端只需要在Timeout內，按照固定的格式回覆Pub訊息，服務端即可同步獲取IoT裝置端的響應結果。
 

具體流程如下：

1536135338761-5846db43-86cb-42b4-bdde-6d
 

1.2 Topic格式約定

請求：/sys/${productKey}/${deviceName}/rrpc/request/${messageId}
響應：/sys/${productKey}/${deviceName}/rrpc/response/${messageId}
$表示變數，每個裝置不同
messageId為IoT平臺生成的訊息ID，裝置端回覆responseTopic裡的messageId要與requestTopic一致

示例：

裝置端需要訂閱:
/sys/${productKey}/${deviceName}/rrpc/request/+
執行中裝置收到Topic：
/sys/PK100101/DN213452/rrpc/request/443859344534
收到訊息後，在timeout時間內回覆Topic：
/sys/PK100101/DN213452/rrpc/response/443859344534
 
 

2.同步呼叫RRPC示例

2.1 裝置端程式碼

 
 

const mqtt = require(`aliyun-iot-mqtt`);
//裝置屬性
const options = require("./iot-device-config.json");
//建立連線
const client = mqtt.getAliyunIotMqttClient(options);

client.subscribe(`/sys/${options.productKey}/${options.deviceName}/rrpc/request/+`)
client.on(`message`, function(topic, message) {
    
    if(topic.indexOf(`/sys/${options.productKey}/${options.deviceName}/rrpc/request/`)>-1){
    	handleRrpc(topic, message)
    }
})

function handleRrpc(topic, message){
	topic = topic.replace(`/request/`,`/response/`);
	console.log("topic=" + topic)
	//普通Rrpc，響應payload自定義
    const payloadJson = {code:200,msg:"handle ok"};
	client.publish(topic, JSON.stringify(payloadJson));
}
 

2.2 服務端POP呼叫Rrpc

 
 
const co = require(`co`);
const RPCClient = require(`@alicloud/pop-core`).RPCClient;

const options = require("./iot-ak-config.json");

//1.初始化client
const client = new RPCClient({
    accessKeyId: options.accessKey,
    secretAccessKey: options.accessKeySecret,
    endpoint: `https://iot.cn-shanghai.aliyuncs.com`,
    apiVersion: `2017-04-20`
});

const payload = {
  "msg": "hello Rrpc"
};

//2.構建request
const params = {
    ProductKey:"a1gMu82K4m2",
    DeviceName:"h5@nuwr5r9hf6l@1532088166923",
    RequestBase64Byte:new Buffer(JSON.stringify(payload)).toString("base64"),
    Timeout:3000
};

co(function*() {
    //3.發起API呼叫
    const response = yield client.request(`Rrpc`, params);

    console.log(JSON.stringify(response));
});
 
rrpc響應：
 
 
{
    "MessageId": "1037292594536681472",
    "RequestId": "D2150496-2A61-4499-8B2A-4B3EC4B2A432",
    "PayloadBase64Byte": "eyJjb2RlIjoyMDAsIm1zZyI6ImhhbmRsZSBvayJ9",
    "Success": true,
    "RrpcCode": "SUCCESS"
}

// PayloadBase64Byte 解碼: {"code":200,"msg":"handle ok"}
 
 

3.物模型-服務同步呼叫InvokeThingService示例

注意：物模型 服務呼叫 介面InvokeThingService，不是Rrpc

3.1 物模型-同步服務定義

1536145308148-48813953-b0b0-4949-b591-1c
 

3.2 裝置端實現

 
 
 
const mqtt = require(`aliyun-iot-mqtt`);
//裝置屬性
const options = require("./iot-device-config.json");
//建立連線
const client = mqtt.getAliyunIotMqttClient(options);

client.subscribe(`/sys/${options.productKey}/${options.deviceName}/rrpc/request/+`)
client.on(`message`, function(topic, message) {
    
    if(topic.indexOf(`/sys/${options.productKey}/${options.deviceName}/rrpc/request/`)>-1){
    	handleRrpc(topic, message)
    }
})
/*
* 如果存在多個同步呼叫服務，需要通過payload裡的method區分
*/
function handleRrpc(topic, message){

	topic = topic.replace(`/request/`,`/response/`);
	console.log("topic=" + topic)
	//物模型 同步服務呼叫，響應payload結構：
    const payloadJson = {
        id: Date.now(),
        code:200,
        data: {
            currentMode: Math.floor((Math.random() * 20) + 10)
        }
    }

	client.publish(topic, JSON.stringify(payloadJson));
}
注意：裝置端響應的payload要滿足物模型定義的出參結構

3.3 服務端POP 介面InvokeThingService

 
 
const co = require(`co`);
const RPCClient = require(`@alicloud/pop-core`).RPCClient;

const options = require("./iot-ak-config.json");

//1.初始化client
const client = new RPCClient({
    accessKeyId: options.accessKey,
    secretAccessKey: options.accessKeySecret,
    endpoint: `https://iot.cn-shanghai.aliyuncs.com`,
    apiVersion: `2018-01-20`
});

const params = {
    ProductKey: "a1gMu82K4m2",
    DeviceName: "h5@nuwr5r9hf6l@1532088166923",
    Args: JSON.stringify({ "mode": "1" }),
    Identifier: "thing.service.setMode"
};

co(function*() {
    try {
        //3.發起API呼叫
        const response = yield client.request(`InvokeThingService`, params);

        console.log(JSON.stringify(response));
    } catch (err) {
        console.log(err);
    }
});
 
呼叫結果：
 
 
{
    "Data":{
        "Result": "{"currentMode":12}",
        "MessageId": "1536145625658"
    },
    "RequestId": "29FD78CE-D1FF-48F7-B0A7-BD52C142DD7F",
    "Success": true
}
 


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