MQTT over SSL with PAHO C - c

Question

I'm trying to figure out how paho works with SSL.
I've tested a simple pub (without SSL) using mosquitto as broker (with default mosquitto.conf) and all works well. Now I've modified the code below (using the ADDRESS define instead of ADDRESSTEST) for testing SSL. I've used the certified provided by the section "test" of paho.
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <MQTTClient.h>
#define ADDRESS "ssl://localhost:18885"
#define ADDRESSTEST "tcp://localhost:1883"
#define CLIENTID "ExampleClientPub"
#define TOPIC "MQTTExamples"
#define PAYLOAD "Hello World!"
#define QOS 1
#define TIMEOUT 10000L
int main() {
MQTTClient client;
MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
MQTTClient_SSLOptions ssl_opts = MQTTClient_SSLOptions_initializer;;
MQTTClient_message pubmsg = MQTTClient_message_initializer;
MQTTClient_deliveryToken token;
int rc;
MQTTClient_create(&client, ADDRESS, CLIENTID,
MQTTCLIENT_PERSISTENCE_DEFAULT, NULL);
conn_opts.keepAliveInterval = 20;
conn_opts.cleansession = 1;
conn_opts.ssl = &ssl_opts;
conn_opts.ssl->trustStore = "../../validpath/test-root-ca.crt";
conn_opts.ssl->keyStore = "../../validpath/client.pem";
conn_opts.serverURIcount = 0;
conn_opts.serverURIs = NULL;
if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
{
printf("Failed to connect, return code %d\n", rc);
exit(EXIT_FAILURE);
}
pubmsg.payload = PAYLOAD;
pubmsg.payloadlen = (int)strlen(PAYLOAD);
pubmsg.qos = QOS;
pubmsg.retained = 0;
MQTTClient_publishMessage(client, TOPIC, &pubmsg, &token);
printf("Waiting for up to %d seconds for publication of %s\n"
"on topic %s for client with ClientID: %s\n",
(int)(TIMEOUT/1000), PAYLOAD, TOPIC, CLIENTID);
rc = MQTTClient_waitForCompletion(client, token, TIMEOUT);
printf("Message with delivery token %d delivered\n", token);
MQTTClient_disconnect(client, 10000);
MQTTClient_destroy(&client);
return 0;
}
The problem is that when i run the software with this configuration, the MQTTClient_connect return me the code MQTTCLIENT_WRONG_MQTT_VERSION. Mosquitto runs in localhost and I've modified the mosquitto.conf in this way:
# server authentication - no client authentication
listener 18885
cafile validpath/all-ca.crt
certfile validpath/server.crt
keyfile validpath/server.key
require_certificate false
#tls_version tlsv1

Answer 1

This problem occurs when you compile with -lpaho-mqtt3c, instead of -lpaho-mqtt3cs (that enable SSL). Now it works properly!