DESCRIPTION

This is an overview of how to use libmosquitto to create MQTT aware client programs. There may be separate man pages on each of the functions described here in the future. There are also bindings for libmosquitto for C++ and Python. They are not documented here.

This is fairly incomplete, please see mosquitto.h for a better description of the functions.

STATUS

The libmosquitto api is currently regarded as experimental and unstable and may change in future releases.

LIBMOSQUITTO SYMBOL NAMES

All public functions in libmosquitto have the prefix "mosquitto_". Any other functions defined in the source code are to be treated as private functions and may change between any release. Do not use these functions!

FUNCTIONS

LIBRARY VERSION

unsigned long mosquitto_lib_version (int *major, int *minor, int *revision);

Obtain version information about the library. If any of major, minor or revision are not NULL they will return the corresponding version numbers. The return value is an integer representation of the complete version number (e.g. 9000 for 0.9) that can be used for comparisons.

LIBRARY INITIALISATION AND CLEANUP

int mosquitto_lib_init (void); int mosquitto_lib_cleanup (void);

CLIENT CONSTRUCTOR/DESTRUCTOR

struct mosquitto *mosquitto_new (const char *id, void *obj); void mosquitto_destroy (struct mosquitto *mosq);

LOGGING

int mosquitto_log_init (struct mosquitto *mosq, int priorities, int destinations);

Configure the logging settings for this client. Returns 0 on success, 1 on error.

Set priorities by ORing any of the items in the following list:

• MOSQ_LOG_INFO
• MOSQ_LOG_NOTICE
• MOSQ_LOG_WARNING
• MOSQ_LOG_ERROR
• MOSQ_LOG_DEBUG

Set destinations by ORing any of the items in the following list:

• MOSQ_LOG_NONE
• MOSQ_LOG_STDOUT
• MOSQ_LOG_STDERR

WILLS

int mosquitto_will_set (struct mosquitto *mosq, bool will, const char *topic, uint32_t payloadlen, const uint8_t *payload, int qos, bool retain);

CONNECT/DISCONNECT

void mosquitto_connect (struct mosquitto *mosq, const char *host, int port, int keepalive, bool clean_session); void mosquitto_reconnect (struct mosquitto *mosq); int mosquitto_disconnect (struct mosquitto *mosq);

PUBLISH

int mosquitto_publish (struct mosquitto *mosq, uint16_t *mid, const char *topic, uint32_t payloadlen, const uint8_t *payload, int qos, bool retain);

SUBSCRIBE/UNSUBSCRIBE

int mosquitto_subscribe (struct mosquitto *mosq, uint16_t *mid, const char *sub, int qos); int mosquitto_unsubscribe (struct mosquitto *mosq, uint16_t *mid, const char *sub);

NETWORK LOOP

int mosquitto_loop (struct mosquitto *mosq, int timeout); int mosquitto_loop_read (struct mosquitto *mosq); int mosquitto_loop_write (struct mosquitto *mosq); int mosquitto_loop_misc (struct mosquitto *mosq); int mosquitto_socket (struct mosquitto *mosq);

CALLBACKS

See mosquitto.h

EXAMPLES

#include <mosquitto.h>
void my_message_callback(void *obj, 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(void *obj, int result)
{
        struct mosquitto *mosq = obj;
        int i;
        if(!result){
                mosquitto_subscribe(mosq, topics[i], topic_qos);
        }else{
                fprintf(stderr, "Connect failed\n");
        }
}
void my_subscribe_callback(void *obj, uint16_t mid, int qos_count, const uint8_t *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");
}
int main(int argc, char *argv[])
{
        char id[30];
        int i;
        char *host = "localhost";
        int port = 1883;
        int keepalive = 60;
        bool clean_session = true;
        struct mosquitto *mosq = NULL;
        mosq = mosquitto_new(id, NULL);
        if(!mosq){
                fprintf(stderr, "Error: Out of memory.\n");
                return 1;
        }
        mosquitto_log_init(mosq, MOSQ_LOG_DEBUG | MOSQ_LOG_ERR | MOSQ_LOG_WARNING
                        | MOSQ_LOG_NOTICE | MOSQ_LOG_INFO, MOSQ_LOG_STDERR);
        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, clean_session)){
                fprintf(stderr, "Unable to connect.\n");
                return 1;
        }
        while(!mosquitto_loop(mosq, -1)){
        }
        mosquitto_destroy(mosq);
        return 0;
}
                

AUTHOR

Roger Light <[email protected]>