mosquitto简单应用

1. 简述

一款实现了消息推送协议 MQTT v3.1 的开源消息代理软件，提供轻量级的，支持可发布/可订阅的的消息推送模式，使设备对设备之间的短消息通信变得简单，比如现在应用广泛的低功耗传感器，手机、嵌入式计算机、微型控制器等移动设备。一个典型的应用案例就是 Andy Stanford-ClarkMosquitto（MQTT协议创始人之一）在家中实现的远程监控和自动化，并在 OggCamp 的演讲上，对MQTT协议进行详细阐述。

官网：

http://www.mosquitto.org/

http://www.mosquitto.org/man/

http://www.mosquitto.org/api/

2. 函数

mosquitto结构体：

struct mosquitto;

struct mosquitto_message{
    int mid;
    char *topic;
    void *payload;
    int payloadlen;
    int qos;
    bool retain;
};

mosquitto支持推送和订阅消息模式：

/* 
 * Function: mosquitto_publish
 *
 * Publish a message on a given topic.
 * 
 * Parameters:
 *  mosq -       a valid mosquitto instance.
 *  mid -        pointer to an int. If not NULL, the function will set this
 *               to the message id of this particular message. This can be then
 *               used with the publish callback to determine when the message
 *               has been sent.
 *               Note that although the MQTT protocol doesn't use message ids
 *               for messages with QoS=0, libmosquitto assigns them message ids
 *               so they can be tracked with this parameter.
 *  topic -      null terminated string of the topic to publish to.
 *  payloadlen - the size of the payload (bytes). Valid values are between 0 and
 *               268,435,455.
 *  payload -    pointer to the data to send. If payloadlen > 0 this must be a
 *               valid memory location.
 *  qos -        integer value 0, 1 or 2 indicating the Quality of Service to be
 *               used for the message.
 *  retain -     set to true to make the message retained.
 *
 * Returns:
 *  MOSQ_ERR_SUCCESS -      on success.
 *  MOSQ_ERR_INVAL -        if the input parameters were invalid.
 *  MOSQ_ERR_NOMEM -        if an out of memory condition occurred.
 *  MOSQ_ERR_NO_CONN -      if the client isn't connected to a broker.
 *  MOSQ_ERR_PROTOCOL -     if there is a protocol error communicating with the
 *                          broker.
 *  MOSQ_ERR_PAYLOAD_SIZE - if payloadlen is too large.
 *
 * See Also: 
 *  <mosquitto_max_inflight_messages_set>
 */
libmosq_EXPORT int mosquitto_publish(struct mosquitto *mosq, int *mid, const char *topic, int payloadlen, const void *payload, int qos, bool retain);

/*
 * Function: mosquitto_subscribe
 *
 * Subscribe to a topic.
 *
 * Parameters:
 *  mosq - a valid mosquitto instance.
 *  mid -  a pointer to an int. If not NULL, the function will set this to
 *         the message id of this particular message. This can be then used
 *         with the subscribe callback to determine when the message has been
 *         sent.
 *  sub -  the subscription pattern.
 *  qos -  the requested Quality of Service for this subscription.
 *
 * Returns:
 *  MOSQ_ERR_SUCCESS - on success.
 *  MOSQ_ERR_INVAL -   if the input parameters were invalid.
 *  MOSQ_ERR_NOMEM -   if an out of memory condition occurred.
 *  MOSQ_ERR_NO_CONN - if the client isn't connected to a broker.
 */
libmosq_EXPORT int mosquitto_subscribe(struct mosquitto *mosq, int *mid, const char *sub, int qos);

/*
 * Function: mosquitto_unsubscribe
 *
 * Unsubscribe from a topic.
 *
 * Parameters:
 *  mosq - a valid mosquitto instance.
 *  mid -  a pointer to an int. If not NULL, the function will set this to
 *         the message id of this particular message. This can be then used
 *         with the unsubscribe callback to determine when the message has been
 *         sent.
 *  sub -  the unsubscription pattern.
 *
 * Returns:
 *  MOSQ_ERR_SUCCESS - on success.
 *  MOSQ_ERR_INVAL -   if the input parameters were invalid.
 *  MOSQ_ERR_NOMEM -   if an out of memory condition occurred.
 *  MOSQ_ERR_NO_CONN - if the client isn't connected to a broker.
 */
libmosq_EXPORT int mosquitto_unsubscribe(struct mosquitto *mosq, int *mid, const char *sub);

一般使用流程如下：

mosquitto_lib_init();
mosq=mosquitto_new();

mosquitto_connect_callback_set();  ----mosquitto_subscribe();
mosquitto_disconnect_callback_set();
mosquitto_message_callback_set();  ----接收解析消息

mosquitto_username_pw_set(mosq, "user", "pw");
mosquitto_connect();
mosquitto_loop(mosq, 20, 10);

mosquitto_publish();

mosquitto_destroy(mosq);
mosquitto_lib_cleanup();

3. 应用

manpage上一个示例：

#include <stdio.h>
#include <mosquitto.h>

void my_message_callback(struct mosquitto *mosq, void *userdata, const struct mosquitto_message *message)
{
    if(message->payloadlen){
        printf("%s %s\n", message->topic, message->payload);
    }else{
        printf("%s (null)\n", message->topic); } fflush(stdout); } void my_connect_callback(struct mosquitto *mosq, void *userdata, int result) { int i; if(!result){ /* Subscribe to broker information topics on successful connect. */ mosquitto_subscribe(mosq, NULL, "$SYS/#", 2); }else{ fprintf(stderr, "Connect failed\n"); } } void my_subscribe_callback(struct mosquitto *mosq, void *userdata, int mid, int qos_count, const int *granted_qos) { int i; printf("Subscribed (mid: %d): %d", mid, granted_qos[0]); for(i=1; i<qos_count; i++){ printf(", %d", granted_qos[i]); } printf("\n"); } void my_log_callback(struct mosquitto *mosq, void *userdata, int level, const char *str) { /* Pring all log messages regardless of level. */ printf("%s\n", str); } int main(int argc, char *argv[]) { int i; char *host = "localhost"; int port = 1883; int keepalive = 60; bool clean_session = true; struct mosquitto *mosq = NULL; mosquitto_lib_init(); mosq = mosquitto_new(NULL, clean_session, NULL); if(!mosq){ fprintf(stderr, "Error: Out of memory.\n"); return 1; } mosquitto_log_callback_set(mosq, my_log_callback); mosquitto_connect_callback_set(mosq, my_connect_callback); mosquitto_message_callback_set(mosq, my_message_callback); mosquitto_subscribe_callback_set(mosq, my_subscribe_callback); if(mosquitto_connect(mosq, host, port, keepalive)){ fprintf(stderr, "Unable to connect.\n"); return 1; } mosquitto_loop_forever(mosq, -1, 1); mosquitto_destroy(mosq); mosquitto_lib_cleanup(); return 0; }

1. 简述

3. 应用

猜你喜欢