Re: [mqtt] mosquitto_connect returns MOSQ_ERR_SUCCESS but connect callback is never called

[Nevadita Chatterjee]

Hi All,

I have enabled TLS for MQTT broker, Here I want to use a specific cipher suit 

[0x9f]

DHE-RSA-AES256-GCM-SHA384

But the MQTT broker is giving Error  OpenSSL Error: error:1408A0C1:SSL routines:ssl3_get_client_hello:no shared cipher 

MQTT broker is only supporting 

[0xc030]

ECDHE-RSA-AES256-GCM-SHA384

Regards,

Nevadita Chatterjee

On Wed, May 29, 2019 at 3:02 PM Javi Jap <occ...@gmail.com> wrote:

Hi,

I am writing a C program to connect to MQTT using mosquitto library. When I try to connect to the broker the mosquitto_connect API returns no error but the connect callback is never called. I am using the same username and password that are working with mosquitto_sub and mosquitto_pub. I don't know what I am missing. This is the code for mqtt connection.

mqtt_connection_t* mqtt_connect(const char* id, const char *host, int port, const char *username, const char *password, mqtt_cb_t *cb)
{
    mqtt_connection_t *conn = g_new0(mqtt_connection_t, 1);
    conn->host = g_strdup(host);
    conn->id = g_strdup(id);
    conn->connected = false;
    conn->callbacks = *cb;
    conn->topics = NULL;
    conn->port = port;

    mosquitto_lib_init();

    int major, minor, revision;
    mosquitto_lib_version(&major, &minor, &revision);

    assert_log_exit_with_msg(!(major < 1 || minor < 5 || revision < 4), "Incompatible libmosquitto version. Minimum version required is v1.5.4");

    conn->mosq = mosquitto_new(id, true, conn);
    if (conn->mosq == NULL)
    {
        log_err("Out of memory");
        goto error;
    }

    // Only allow one message to be queued in the Mosquitto library
    mosquitto_max_inflight_messages_set(conn->mosq, 1);
    // Exponential backoff between 3 and 60 seconds
    mosquitto_reconnect_delay_set(conn->mosq, 3, 60, true);
    mosquitto_opts_set(conn->mosq, MOSQ_OPT_PROTOCOL_VERSION, (char*)"MQTT_PROTOCOL_V311");
    if (mosquitto_tls_set(conn->mosq, NULL, "/etc/ssl/certs", NULL, NULL, NULL) != MOSQ_ERR_SUCCESS)
    {
        log_err("Failed to set MQTT client TLS options");
        goto error;
    }
    if (mosquitto_tls_opts_set(conn->mosq, 1, "tlsv1.2", NULL) != MOSQ_ERR_SUCCESS)
    {
        log_err("Failed to set MQTT client TLS version");
        goto error;
    }

    mosquitto_username_pw_set(conn->mosq, username, password);

    mosquitto_log_callback_set(conn->mosq, log_callback);
    mosquitto_message_callback_set(conn->mosq, message_callback);
    mosquitto_publish_callback_set(conn->mosq, publish_callback);
    mosquitto_connect_callback_set(conn->mosq, connect_callback);       // <--------------- here I set the connect callback
    mosquitto_disconnect_callback_set(conn->mosq, disconnect_callback);

    log_info("Connecting to %s on port %d with ID %s", conn->host, conn->port, conn->id);
    int status = mosquitto_connect(conn->mosq, conn->host, conn->port, MQTT_DEFAULT_KEEPALIVE); //<--------- THIS RETURNS MOSQ_ERR_SUCCESS but the connect callback is never called
    if (status != MOSQ_ERR_SUCCESS)
    {
        log_err("Unable to connect to broker: %s", mosquitto_strerror(status));
        return conn;
    }

    int fd = mosquitto_socket(conn->mosq);
    if (fd < 0)
    {
        log_err("Unable to get socket handle");
        return conn;
    }

    conn->source = g_unix_fd_add(fd, G_IO_IN, (GUnixFDSourceFunc)do_mosquitto_event, conn);

    return conn;

error:
    mqtt_disconnect(conn);
    return NULL;
}

I have enabled all the logs in mosquitto config file seting log_type all, and I've been looking into the logs but with no luck.

Any idea of how to fix/debug this?

Thanks!

Javi

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