openssl_publisher.c

Same program as simple_publisher.c, but over an encrypted connection using OpenSSL.

Usage:

./bin/openssl_publisher ca_file [address [port [topic]]]

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>

#include <mqtt.h>
#include "templates/openssl_sockets.h"


void publish_callback(void** unused, struct mqtt_response_publish *published);

void* client_refresher(void* client);

void exit_example(int status, BIO* sockfd, pthread_t *client_daemon);

int main(int argc, const char *argv[]) 
{
    const char* addr;
    const char* port;
    const char* topic;
    const char* ca_file;

    /* Load OpenSSL */
    SSL_load_error_strings();
    ERR_load_BIO_strings();
    OpenSSL_add_all_algorithms();
    SSL_library_init();

    SSL_CTX* ssl_ctx;
    BIO* sockfd;

    if (argc > 1) {
        ca_file = argv[1];
    } else {
        printf("error: path to the CA certificate to use\n");
        exit(1);
    }

    /* get address (argv[2] if present) */
    if (argc > 2) {
        addr = argv[2];
    } else {
        addr = "test.mosquitto.org";
    }

    /* get port number (argv[3] if present) */
    if (argc > 3) {
        port = argv[3];
    } else {
        port = "8883";
    }

    /* get the topic name to publish */
    if (argc > 4) {
        topic = argv[4];
    } else {
        topic = "datetime";
    }

    /* open the non-blocking TCP socket (connecting to the broker) */
    open_nb_socket(&sockfd, &ssl_ctx, addr, port, ca_file, NULL);

    if (sockfd == NULL) {
        exit_example(EXIT_FAILURE, sockfd, NULL);
    }

    /* setup a client */
    struct mqtt_client client;
    uint8_t sendbuf[2048]; /* sendbuf should be large enough to hold multiple whole mqtt messages */
    uint8_t recvbuf[1024]; /* recvbuf should be large enough any whole mqtt message expected to be received */
    mqtt_init(&client, sockfd, sendbuf, sizeof(sendbuf), recvbuf, sizeof(recvbuf), publish_callback);
    mqtt_connect(&client, "publishing_client", NULL, NULL, 0, NULL, NULL, 0, 400);

    /* check that we don't have any errors */
    if (client.error != MQTT_OK) {
        fprintf(stderr, "error: %s\n", mqtt_error_str(client.error));
        exit_example(EXIT_FAILURE, sockfd, NULL);
    }

    /* start a thread to refresh the client (handle egress and ingree client traffic) */
    pthread_t client_daemon;
    if(pthread_create(&client_daemon, NULL, client_refresher, &client)) {
        fprintf(stderr, "Failed to start client daemon.\n");
        exit_example(EXIT_FAILURE, sockfd, NULL);

    }

    /* start publishing the time */
    printf("%s is ready to begin publishing the time.\n", argv[0]);
    printf("Press ENTER to publish the current time.\n");
    printf("Press CTRL-D (or any other key) to exit.\n\n");
    while(fgetc(stdin) == '\n') {
        /* get the current time */
        time_t timer;
        time(&timer);
        struct tm* tm_info = localtime(&timer);
        char timebuf[26];
        strftime(timebuf, 26, "%Y-%m-%d %H:%M:%S", tm_info);

        /* print a message */
        char application_message[256];
        snprintf(application_message, sizeof(application_message), "The time is %s", timebuf);
        printf("%s published : \"%s\"", argv[0], application_message);

        /* publish the time */
        mqtt_publish(&client, topic, application_message, strlen(application_message) + 1, MQTT_PUBLISH_QOS_2);

        /* check for errors */
        if (client.error != MQTT_OK) {
            fprintf(stderr, "error: %s\n", mqtt_error_str(client.error));
            exit_example(EXIT_FAILURE, sockfd, &client_daemon);
        }
    }   

    /* disconnect */
    printf("\n%s disconnecting from %s\n", argv[0], addr);
    sleep(1);

    /* exit */ 
    exit_example(EXIT_SUCCESS, sockfd, &client_daemon);
}

void exit_example(int status, BIO* sockfd, pthread_t *client_daemon)
{
    if (sockfd != NULL) BIO_free_all(sockfd);
    if (client_daemon != NULL) pthread_cancel(*client_daemon);
    exit(status);
}



void publish_callback(void** unused, struct mqtt_response_publish *published) 
{
    /* not used in this example */
}

void* client_refresher(void* client)
{
    while(1) 
    {
        mqtt_sync((struct mqtt_client*) client);
        usleep(100000U);
    }
    return NULL;
}