1.同步调用场景
1.1 背景
MQTT协议是基于PUB/SUB的异步通信模式，无法实现服务端下发指令给设备端，同时需要设备端返回响应结果的场景。
IoT物联网平台基于MQTT协议制定了一套请求和响应的同步机制，无需改动MQTT协议即可实现同步通信。应用服务器通过POP API发起Rrpc调用，IoT设备端只需要在Timeout内，按照固定的格式回复Pub消息，服务端即可同步获取IoT设备端的响应结果。
具体流程如下：
1.2 Topic格式约定
请求：/sys/${productKey}/${deviceName}/rrpc/request/${messageId}
响应：/sys/${productKey}/${deviceName}/rrpc/response/${messageId}
$表示变量，每个设备不同messageId为IoT平台生成的消息ID，设备端回复responseTopic里的messageId要与requestTopic一致
示例：
设备端需要订阅:
/sys/${productKey}/${deviceName}/rrpc/request/+
运行中设备收到Topic：
/sys/PK100101/DN213452/rrpc/request/443859344534
收到消息后，在timeout时间内回复Topic：
/sys/PK100101/DN213452/rrpc/response/443859344534
2.同步调用RRPC示例
2.1 设备端代码
const mqtt = require('aliyun-iot-mqtt');
//设备属性
const options = require("./iot-device-config.json");
//建立连接
const client = mqtt.getAliyunIotMqttClient(options);
client.subscribe(`/sys/${options.productKey}/${options.deviceName}/rrpc/request/+`)
client.on('message', function(topic, message) {
if(topic.indexOf(`/sys/${options.productKey}/${options.deviceName}/rrpc/request/`)>-1){
handleRrpc(topic, message)
}
})
function handleRrpc(topic, message){
topic = topic.replace('/request/','/response/');
console.log("topic=" + topic)
//普通Rrpc，响应payload自定义
const payloadJson = {code:200,msg:"handle ok"};
client.publish(topic, JSON.stringify(payloadJson));
}
2.2 服务端POP调用Rrpc
const co = require('co');
const RPCClient = require('@alicloud/pop-core').RPCClient;
const options = require("./iot-ak-config.json");
//1.初始化client
const client = new RPCClient({
accessKeyId: options.accessKey,
secretAccessKey: options.accessKeySecret,
endpoint: 'https://iot.cn-shanghai.aliyuncs.com',
apiVersion: '2017-04-20'
});
const payload = {
"msg": "hello Rrpc"
};
//2.构建request
const params = {
ProductKey:"a1gMu82K4m2",
DeviceName:"h5@nuwr5r9hf6l@1532088166923",
RequestBase64Byte:new Buffer(JSON.stringify(payload)).toString("base64"),
Timeout:3000
};
co(function*() {
//3.发起API调用
const response = yield client.request('Rrpc', params);
console.log(JSON.stringify(response));
});
rrpc响应：
{
"MessageId": "1037292594536681472",
"RequestId": "D2150496-2A61-4499-8B2A-4B3EC4B2A432",
"PayloadBase64Byte": "eyJjb2RlIjoyMDAsIm1zZyI6ImhhbmRsZSBvayJ9",
"Success": true,
"RrpcCode": "SUCCESS"
}
// PayloadBase64Byte 解码: {"code":200,"msg":"handle ok"}
3.物模型-服务同步调用InvokeThingService示例
注意：物模型 服务调用 接口InvokeThingService，不是Rrpc
3.1 物模型-同步服务定义
3.2 设备端实现
const mqtt = require('aliyun-iot-mqtt');
//设备属性
const options = require("./iot-device-config.json");
//建立连接
const client = mqtt.getAliyunIotMqttClient(options);
client.subscribe(`/sys/${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)
}
})
/*
* 如果存在多个同步调用服务，需要通过payload里的method区分
*/
function handleRrpc(topic, message){
topic = topic.replace('/request/','/response/');
console.log("topic=" + topic)
//物模型 同步服务调用，响应payload结构：
const payloadJson = {
id: Date.now(),
code:200,
data: {
currentMode: Math.floor((Math.random() * 20) + 10)
}
}
client.publish(topic, JSON.stringify(payloadJson));
}
注意：设备端响应的payload要满足物模型定义的出参结构
3.3 服务端POP 接口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.发起API调用
const response = yield client.request('InvokeThingService', params);
console.log(JSON.stringify(response));
} catch (err) {
console.log(err);
}
});
调用结果：
{
"Data":{
"Result": "{\"currentMode\":12}",
"MessageId": "1536145625658"
},
"RequestId": "29FD78CE-D1FF-48F7-B0A7-BD52C142DD7F",
"Success": true
}
