I am trying to do MQTT overs TLS using PubSubClient and the WiFiSecureClient. Everything works as expected with plain TCP sockets and AtWifi.h's WiFiClient. However, I can’t seem to get it to work over TLS, although the initial connection seems to be working (i.e. CA is correctly setup).
It would appear WiFiClientSecure#connected() is blocking when trying to do ssl_client#data_to_read() - I wonder if something needs to be changed so that the call to mbed_ssl_read actually returns, even when 0 bytes are available, which doesn’t seem to be the case at the moment?
Full example below – if I remove the checks “if client.connected()” in the publish() and subscribe() method of the PubSubClient, it works around the issue.
#include <Arduino.h>
#include <AtWifi.h>
#include <WiFiClientSecure.h>
#include <PubSubClient.h>
#include "iot_config.h"
const char *ssid = IOT_CONFIG_WIFI_SSID;
const char *password = IOT_CONFIG_WIFI_PASSWORD;
//WiFiClient wifiClient;
WiFiClientSecure wifiClient;
PubSubClient mqttClient(wifiClient);
void connectToWifi();
void connectMQTT();
void callback(char *topic, byte *payload, unsigned int length)
{
Serial.print("Message arrived [");
Serial.print(topic);
Serial.print("] ");
for (int i = 0; i < length; i++)
{
Serial.print((char)payload[i]);
}
Serial.println();
}
void setup()
{
//Initialize serial and wait for port to open:
Serial.begin(115200);
while (!Serial)
; // Wait for Serial to be ready
delay(1000);
connectToWifi();
wifiClient.setCACert("-----BEGIN CERTIFICATE-----\n"
"foobar\n"
"-----END CERTIFICATE-----");
mqttClient.setServer("xxx.net", 8883);
mqttClient.setCallback(callback);
connectMQTT();
}
void loop()
{
mqttClient.loop();
}
void connectToWifi()
{
Serial.print("Attempting to connect to SSID: ");
Serial.println(ssid);
WiFi.begin(ssid, password);
// attempt to connect to Wifi network:
while (WiFi.status() != WL_CONNECTED)
{
Serial.print(".");
// wait 1 second for re-trying
delay(1000);
}
Serial.print("Connected to ");
Serial.println(ssid);
// wifiClient.setCACert(baltimore_root_ca);
}
void connectMQTT()
{
while (!mqttClient.connected())
{
Serial.print("Attempting MQTT connection...");
// Attempt to connect
if (mqttClient.connect("wioTerminal"))
{
Serial.println("connected");
// Once connected, publish an announcement...
mqttClient.publish("outTopic", "hello world!");
// ... and resubscribe
mqttClient.subscribe("inTopic");
while (mqttClient.connected())
{
mqttClient.publish("outTopic", "hello");
delay(5000);
}
}
else
{
Serial.print("failed, rc=");
Serial.print(mqttClient.state());
Serial.println(" try again in 5 seconds");
// Wait 5 seconds before retrying
delay(5000);
}
}
}```