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system_mqtt.cpp
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system_mqtt.cpp
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/* MQTT client
* Based on the example in https://github.com/256dpi/arduino-mqtt
*
* Configuration
* Required: SYSTEM_MQTT_SSID SYSTEM_MQTT_PASSWORD SYSTEM_MQTT_SERVER SYSTEM_MQTT_MS
* Optional: ESP8266 SYSTEM_MQTT_DEBUG SYSTEM_WIFI_WANT SYSTEM_MQTT_LOOPBACK
*
*/
#include "_settings.h"
#ifdef SYSTEM_MQTT_WANT
#if ESP8266 // Note ESP8266 and ESP32 are defined for respective chips - unclear if anything like that for other Arduinos
#include <ESP8266WiFi.h> // for WiFiClient
#else
#include <WiFi.h> // This will be platform dependent, will work on ESP32 but most likely want configurration for other chips/boards
#endif
#include <MQTT.h>
// If configred not to use Wifi (or in future BLE) then will just operate locally, sending MQTT between components on this node, but
// not elsewhere.
// TODO add support for BLE if it makes sense for MQTT
#ifdef SYSTEM_WIFI_WANT
#include "system_wifi.h" // xWifi
#endif //SYSTEM_WIFI_WANT
namespace xMqtt {
#ifdef SYSTEM_WIFI_WANT
WiFiClient net;
MQTTClient client(512,128); //TODO 29 large receive buffer as Advert bounces bacj
#endif // SYSTEM_WIFI_WANT
unsigned long nextLoopTime = 0;
// The subscription class manages a list of subscription topics & callbacks.
// It is not totally self contained as it knows how to call the client to subscribe and how to dispatch.
class Subscription {
public:
static Subscription *subscriptions;
String *topic;
MQTTClientCallbackSimple cb;
Subscription *next;
//Subscription() { topic = NULL; cb = NULL; next = NULL}
Subscription(String &t, MQTTClientCallbackSimple c, Subscription* n) {
topic = &t;
cb = c;
next = n;
};
static Subscription *find(String &t) {
Subscription *i;
for (i = subscriptions; i && (*i->topic != t); i = i->next) {
}
return i; // Found or not found case both return here
}
static void subscribe(String &topic, MQTTClientCallbackSimple cb) {
Subscription *existingSub = find(topic);
subscriptions = new Subscription(topic, cb, subscriptions);
if (!existingSub) {
#ifdef SYSTEM_WIFI_WANT
if (!client.subscribe(topic)) {
#ifdef SYSTEM_MQTT_DEBUG
Serial.println("MQTT Subscription failed to ");
Serial.print(topic);
#endif // SYSTEM_MQTT_DEBUG
};
#endif // SYSTEM_WIFI_WANT
}
#ifdef SYSTEM_MQTT_DEBUG
Serial.println("Subscribing to: " + topic);
#endif // SYSTEM_MQTT_DEBUG
}
static void dispatch(String &topic, String &payload) {
Subscription *sub;
for (sub = subscriptions; sub; sub = sub->next) {
if (*sub->topic == topic) {
#ifdef SYSTEM_MQTT_DEBUG
Serial.println("Dispatching: "+topic);
#endif // SYSTEM_MQTT_DEBUG
sub->cb(topic, payload);
}
// debugging if needed to figure out why the comparisom above was mismatching
// else { Serial.println("No match "+*(sub->topic)+" "+topic); }
}
}
static void resubscribeAll() {
#ifdef SYSTEM_WIFI_WANT
Subscription *sub;
#ifdef SYSTEM_MQTT_DEBUG
Serial.print("Resubscribing: ");
#endif // SYSTEM_MQTT_DEBUG
for (sub = subscriptions; sub; sub = sub->next) {
if (!client.subscribe(*(sub->topic))) {
#ifdef SYSTEM_MQTT_DEBUG
Serial.print("MQTT resubscription failed to ");
#endif // SYSTEM_MQTT_DEBUG
}
#ifdef SYSTEM_MQTT_DEBUG
Serial.print(" " + *(sub->topic));
#endif // SYSTEM_MQTT_DEBUG
}
#ifdef SYSTEM_MQTT_DEBUG
Serial.println();
#endif; // SYSTEM_MQTT_DEBUG
#endif //SYSTEM_WIFI_WANT
}
};
Subscription *Subscription::subscriptions = NULL;
// A data structure that represents a single MQTT message
class Message {
public:
String *topic;
String *message;
bool retain;
int qos;
Message *next; // Allows a chain of them in a queue
Message(String &t, String &m, bool r, int q) {
topic = &t;
message = &m;
retain = r;
qos = q;
next = NULL;
}
};
class MessageList {
public:
MessageList() {
top = NULL;
}
Message *find(String &t) {
Message *i;
for (i = top; i && (*i->topic != t); i = i->next) {
}
return i; // Found or not found case both return here
}
void push(Message *m) {
m->next = top;
top = m;
}
Message *shift() {
Message *i = top;
Message *j;
if (!i) return NULL;
for (;i->next;(j=i, i = i->next)) {}
j->next = NULL;
return i;
}
void retain(Message *m) {
Message *f = find(*m->topic);
if (f) {
f->message = m->message;
} else {
push(m);
}
}
private:
Message *top;
};
// A data structure that retains the most recent payload for any topic that has been sent at least once.
// It is intended to retain this value on both outgoing and incoming messages so that it can operate in a disconnected network.
MessageList retained;
// A list of messages waiting to be sent.
MessageList queued;
#ifdef SYSTEM_WIFI_WANT // Until we have BLE, compiling without WIFI means just work locally.
bool connect() {
xWifi::checkConnected(); // TODO-22 - blocking and potential puts portal up, may prefer some kind of reconnect
if (client.connected()) {
return true;
} else {
#ifdef SYSTEM_MQTT_DEBUG
Serial.print("\nMQTT connecting: to ");
Serial.print(xWifi::mqtt_host.c_str());
#endif
if (client.connect("arduino", "public", "public")) { // TODO-21 parameterize this
#ifdef SYSTEM_MQTT_DEBUG
Serial.println("Connected");
#endif
Subscription::resubscribeAll();
return true;
} else {
return false;
}
}
}
#endif // SYSTEM_WIFI_WANT
// Inside the receiver its not allowed to send messages, at least with qos != 0;
bool inReceived = false;
// Note this is called both as a callback from client.onMessage and from messageSend if SYSTEM_MQTT_LOOPBACK
void messageReceived(String &topic, String &payload) {
#ifdef SYSTEM_MQTT_DEBUG
Serial.println("MQTT incoming: " + topic + " - " + payload);
#endif
inReceived = true;
// Note: Do not use the client in the callback to publish, subscribe or
// unsubscribe as it may cause deadlocks when other things arrive while
// sending and receiving acknowledgments. Instead, change a global variable,
// or push to a queue and handle it in the loop after calling `client.loop()`.
Subscription::dispatch(topic, payload);
inReceived = false;
}
void messageReceived(Message *m) {
messageReceived(*m->topic, *m->message);
}
void subscribe(String &topic, MQTTClientCallbackSimple cb) {
Subscription::subscribe(topic, cb);
// If we have retained a previous message for this topic then send to client
if (Message *r = retained.find(topic)) {
messageReceived(r);
}
}
// If retain is set, then the broker will keep a copy
// TODO implement qos on broker in this library
// qos: 0 = send at most once; 1 = send at least once; 2 = send exactly once
// These are intentionally required parameters rather than defaulting so the coder thinks about the desired behavior
void messageSendInner(Message *m) {
#ifdef SYSTEM_WIFI_WANT
if (!client.publish(*m->topic, *m->message, m->retain, m->qos)) {
#ifdef SYSTEM_MQTT_DEBUG
Serial.print("Failed to publish");
Serial.print(*m->topic);
Serial.print('=');
Serial.println(*m->message);
#endif // SYSTEM_MQTT_DEBUG
};
#endif // SYSTEM_WIFI_WANT
}
void messageSend(String &topic, String &payload, bool retain, int qos) {
// TODO-21-sema also queue if WiFi is down and qos>0 - not worth doing till xWifi::connect is non-blocking
Message *m = new Message(topic, payload, retain, qos);
if (inReceived && qos) {
queued.push(m);
} else {
messageSendInner(m);
}
// Whether send to net or queue, send loopback and do the retention stuff.
#ifdef SYSTEM_MQTT_LOOPBACK
// This does a local loopback, if anything is listening for this message it will get it twice - once locally and once via server.
if (m->retain) {
retained.retain(m); // Keep a copy of outgoing, so local subscribers will see
}
messageReceived(m);
#endif // SYSTEM_MQTT_LOOPBACK
}
void messageSend(String &topic, float &value, int width, bool retain, int qos) {
String *foo = new String(value, width);
messageSend(topic, *foo, retain, qos);
}
void messageSend(String &topic, int value, bool retain, int qos) {
String *foo = new String(value);
messageSend(topic, *foo, retain, qos);
}
void messageSendQueued() {
Message *m;
for (;!inReceived && (m = queued.shift()); messageSendInner(m)) {}
}
void setup() {
#ifdef SYSTEM_WIFI_WANT // Until have BLE, no WIFI means local only
// Note: Local domain names (e.g. "Computer.local" on OSX) are not supported
// by Arduino. You need to set the IP address directly.
client.begin(xWifi::mqtt_host.c_str(), net);
client.onMessage(messageReceived); // Called back from client.loop
// Note WiFi should be connected by this point but will check here anyway
while (!connect()) {
#ifdef SYSTEM_MQTT_DEBUG
Serial.print(".");
#endif
delay(1000); // Block waiting for WiFi and MQTT to connect
}
#endif // SYSTEM_WIFI_WANT
}
void loop() {
#ifdef SYSTEM_WIFI_WANT // Until have BLE, no WIFI means local only
if (nextLoopTime <= millis()) {
// Automatically reconnect
if (!client.connected()) {
if (!connect()) { // Non blocking but skip client.loop. Note if fails to connect will set nextLoopTime in 1000 ms.
nextLoopTime = millis() + 1000; // If non-blocking then dont do any MQTT for a second then try connect again
}
} else {
messageSendQueued();
if (!client.loop()) {
#ifdef SYSTEM_MQTT_DEBUG
Serial.print("MQTT client loop failed ");
lwmqtt_err_t err = client.lastError();
Serial.println(err);
#endif // SYSTEM_MQTT_DEBUG
}; // Do this at end of loop so some time before checks if connected
nextLoopTime = millis() + SYSTEM_MQTT_MS;
}
}
#endif // SYSTEM_WIFI_WANT
}
} // Namespace xMqtt
#endif //SYSTEM_MQTT_WANT