[经验]

在鸿蒙系统上使用MQTT编程

2020-11-21 18:27:31

1259 鸿蒙系统

我们使用的是paho mqtt软件包，这里介绍一下怎么使用mqtt协议编程。关于鸿蒙系统的mqtt移植好的软件包，相关github链接如下：
https://gitee.com/qidiyun/hARMony_mqtt
这里提供一个简单的编程示例：
这里我们使用MQTTClient编程模型，他支持多任务多线程，非常适合用在鸿蒙系统上。

1. 网络初始化
这里定义一个 Network 结构体，然后指定我们的MQTT服务器的IP和端口号。
Network n; //初始化结构体 NetworkInit(&n); //连接到指定的MQTT服务器IP、端口号 NetworkConnect(&n, “XXX.XXX.XXX.XXX”, XXXX);
2. 设置MQTT缓存和启动MQTT线程
我们这里使用的是MQTT线程功能。
MQTTClientinit(&c, &n, 1000, buf, 100, readbuf, 100); MQTTStartTask(&c);
3. 设置MQTT相关参数
接下来我们设置MQTT的相关参数，包括版本号、客户端ID、账户密码等
MQTTPacket_connectData data = MQTTPacket_connectData_initializer;  data.willFlag = 0; //MQTT版本为 v3 data.MQTTVersion = 3; //设置客户端ID data.clientID.cstring = opts.clientid; //设置客户端账户 data.username.cstring = opts.username; //设置客户端密码 data.password.cstring = opts.password; data.keepAliveInterval = 10; data.cleansession = 1; //连接到MQTT服务器 rc = MQTTConnect(&c, &data);
4. 订阅主题和接收消息
订阅主题可以使用如下函数
MQTTSubscribe(&c, topic, opts.qos, messageArrived);它的函数原型如下：
DLLExport int MQTTSubscribe(MQTTClient* client, const char* topicFilter, enum QoS, messageHandler);其中：
MQTTClient* c ：我们前面定义的MQTTClient结构体
const char* topicFilter：订阅的主题
messageHandler messageHandler ：接收到主题信息后的回调处理函数。
例如上面我们的回调函数是  messageArrived ，它的原型如下：
void messageArrived(MessageData* md){ MQTTMessage* message = md->message; //打印接收到的消息的长度、和消息内容 printf("%.*s", (int)message->payloadlen, (char*)message->payload);}
5. 发送消息
发送消息也比较简单，我们只需要设置好我们的主题和消息内容即可
memset(&pubmsg, '', sizeof(pubmsg)); //消息内容为 hello harmonyOS ! pubmsg.payload = (void*)"hello harmonyOS !"; //消息长度 pubmsg.payloadlen = strlen((char*)pubmsg.payload); pubmsg.qos = QOS0; pubmsg.retained = 0; pubmsg.dup = 0; //推送消息，主题为 pubtest MQTTPublish(&c, "pubtest", &pubmsg);
完整源码如下：
#include #include #include "ohos_init.h"#include "cmsis_os2.h"#include #include "hi_wifi_api.h"//#include "wifi_sta.h"#include "lwip/ip_addr.h"#include "lwip/netifapi.h"#include "lwip/sockets.h"#include "MQTTClient.h"/** * MQTT URI farmat: * domain mode * tcp://iot.eclipse.org:1883 * * ipv4 mode * tcp://192.168.10.1:1883 * ssl://192.168.10.1:1884 * * ipv6 mode * tcp://[fe80::20c:29ff:fe9a:a07e]:1883 * ssl://[fe80::20c:29ff:fe9a:a07e]:1884 */#define MQTT_URI             "tcp://106.13.62.194:1883"struct opts_struct{ char* clientid; int nodelimiter; char* delimiter; enum QoS qos; char* username; char* password; char* host; int port; int showtopics;} opts ={ (char*)"stdout-subscriber", 0, (char*)"n", QOS2, NULL, NULL, (char*)"106.13.62.194", 1883, 1};void messageArrived(MessageData* md){ MQTTMessage* message = md->message; if (opts.showtopics) printf("%.*st", md->topicName->lenstring.len, md->topicName->lenstring.data); if (opts.nodelimiter) printf("%.*s", (int)message->payloadlen, (char*)message->payload); else printf("%.*s%s", (int)message->payloadlen, (char*)message->payload, opts.delimiter); //fflush(stdout);}unsigned char buf[100];unsigned char readbuf[100];int mqtt_test(void){ int rc = 0; MQTTMessage pubmsg; char* topic = "test"; if (strchr(topic, '#') || strchr(topic, '+')) opts.showtopics = 1; if (opts.showtopics) printf("topic is %sn", topic); Network n; MQTTClient c; NetworkInit(&n); NetworkConnect(&n, opts.host, opts.port); MQTTClientInit(&c, &n, 1000, buf, 100, readbuf, 100); MQTTStartTask(&c); MQTTPacket_connectData data = MQTTPacket_connectData_initializer;    data.willFlag = 0; data.MQTTVersion = 3; data.clientID.cstring = opts.clientid; data.username.cstring = opts.username; data.password.cstring = opts.password; data.keepAliveInterval = 10; data.cleansession = 1; printf("Connecting to %s %dn", opts.host, opts.port); rc = MQTTConnect(&c, &data); printf("Connected %dn", rc);       printf("Subscribing to %sn", topic); rc = MQTTSubscribe(&c, topic, opts.qos, messageArrived); printf("Subscribed %dn", rc); memset(&pubmsg, '', sizeof(pubmsg));    pubmsg.payload = (void*)"hello harmonyOS !";    pubmsg.payloadlen = strlen((char*)pubmsg.payload);    pubmsg.qos = QOS0;    pubmsg.retained = 0;    pubmsg.dup = 0; while (1) { MQTTPublish(&c, "pubtest", &pubmsg); sleep(1); } printf("Stoppingn"); MQTTDisconnect(&c); NetworkDisconnect(&n); return 0;}