用简单c程序替换官网thingsboard-gateway的python程序

官网的gateway是用python写的，这在imx6ull等资源有限的cpu上基本带不动。但又需要借助网关功能将设备信息传输到iot平台。这种情况就可以自己写个简单的功能替换掉python程序。

1 mqtt连接iot平台：

mqtt_init(gateway.gwName, addr, gateway.gwAccessToken, NULL, (MSG_RECIVE_CALLBACL)gw_recive_msg_callback);

其中addr为“IP:端口”格式，gwAccessToken为iot平台上该网关对应的token

2 需要订阅的topic

    //device subscribe
    i32 ret = mqtt_subscribe(gateway.handle, ATTRIBUTES_TOPIC, ONECE_LATEST);
    ret |= mqtt_subscribe(gateway.handle, ATTRIBUTES_TOPIC_RESPONSE_ANY, ONECE_LATEST);
    ret |= mqtt_subscribe(gateway.handle, RPC_REQUEST_TOPIC_ANY, ONECE_LATEST);
    ret |= mqtt_subscribe(gateway.handle, RPC_RESPONSE_TOPIC_ANY, ONECE_LATEST);

    //gateway subscribe
    ret |= mqtt_subscribe(gateway.handle, GATEWAY_ATTRIBUTES_TOPIC, ONECE_LATEST);
    ret |= mqtt_subscribe(gateway.handle, GATEWAY_ATTRIBUTES_RESPONSE_TOPIC, ONECE_LATEST);
    ret |= mqtt_subscribe(gateway.handle, GATEWAY_RPC_TOPIC, ONECE_LATEST);

其中宏定义如下

#define GATEWAY_ATTRIBUTES_TOPIC "v1/gateway/attributes"
#define GATEWAY_TELEMETRY_TOPIC "v1/gateway/telemetry"
#define GATEWAY_ATTRIBUTES_REQUEST_TOPIC "v1/gateway/attributes/request"
#define GATEWAY_ATTRIBUTES_RESPONSE_TOPIC "v1/gateway/attributes/response"
#define GATEWAY_MAIN_TOPIC "v1/gateway/"
#define GATEWAY_TOPIC_CONNECT "v1/gateway/connect"
#define GATEWAY_TOPIC_DISCONNECT "v1/gateway/disconnect"
#define GATEWAY_RPC_TOPIC "v1/gateway/rpc"
#define GATEWAY_RPC_RESPONSE_TOPIC "v1/gateway/rpc/response"
#define GATEWAY_CLAIMING_TOPIC "v1/gateway/claim"

#define RPC_RESPONSE_TOPIC "v1/devices/me/rpc/response/"
#define RPC_RESPONSE_TOPIC_ANY "v1/devices/me/rpc/response/+"
#define RPC_REQUEST_TOPIC "v1/devices/me/rpc/request/"
#define RPC_REQUEST_TOPIC_ANY "v1/devices/me/rpc/request/+"
#define ATTRIBUTES_TOPIC "v1/devices/me/attributes"
#define ATTRIBUTES_TOPIC_RESPONSE_ANY "v1/devices/me/attributes/response/+"
#define ATTRIBUTES_TOPIC_REQUEST "v1/devices/me/attributes/request/"
#define ATTRIBUTES_TOPIC_RESPONSE "v1/devices/me/attributes/response/"
#define TELEMETRY_TOPIC "v1/devices/me/telemetry"
#define CLAIMING_TOPIC "v1/devices/me/claim"

3 网关属性上传，网关需要上传一些属性时，可以使用此topic上传

topic为: 
v1/devices/me/attributes

数据格式为:
{"devType":"gateway","uptime":2}

也可以在前面添加ts关键字段
{"ts":1606214325915,"values":{"devType":"gateway","uptime":2}}

4 设备上报属性前要先发送连接信息，否则iot会生成一个类型为default的设备

topic为: 
v1/gateway/connect

数据格式为：
{"device":"123456","type":"led"}

5 设备掉线后，可以向平台发送离线信息

topic为：
v1/gateway/disconnect

数据格式为：
{"device":"123456","type":"led"}

6 设备发送属性字段

topic为: 
v1/gateway/attributes

数据格式为：
{"123456":[{"msgType":"live","counter":0}]}

7 设备发送遥测数据

topic为: 
v1/gateway/telemetry

数据格式为：
{"123456":[{"msgType":"live","counter":0}]}

8 接收远程rpc信息

需关注的topic为：
v1/gateway/rpc

接收到的数据格式：
{"device":"123456","data":{"id":0,"method":"setValue","params":{"msgType":"set","devType":2,"ledColor":"green"}}}

这样就基本满足设备与iot平台的通信要求了。