mqtt: refactoring & mdns autoconnect tweaks

- generic mdns query function so we don't forget about the removeQuery()
- full handle mdns logic in the mqtt module, check for running mdns
instance and periodically poll for _mqtt._tcp service
- autoconnect only when MQTT is enabled *and* there is no server
- use mqtt::settings and mqtt::build namespaces for settings
- some refactoring for topic <-> setting application
- prefer const String& to const char* in topic generation

code/espurna/homeassistant.cpp

@@ -622,7 +622,7 @@ class SensorDiscovery : public Discovery {
  json["uniq_id"] = uniqueId();
 
  json["name"] = _ctx.name() + ' ' + name() + ' ' + localId();
- json["stat_t"] = mqttTopic(magnitudeTopicIndex(_index).c_str(), false);
+ json["stat_t"] = mqttTopic(magnitudeTopicIndex(_index), false);
  json["unit_of_meas"] = magnitudeUnits(_index);
 
  json.printTo(_message);

code/espurna/mdns.cpp

@@ -11,27 +11,12 @@ Copyright (C) 2017-2019 by Xose Pérez <xose dot perez at gmail dot com>
 // -----------------------------------------------------------------------------
 
 #include "mdns.h"
-
-#include "mqtt.h"
 #include "utils.h"
 
 #if MDNS_SERVER_SUPPORT
 
 #include <ESP8266mDNS.h>
 
-#if MQTT_SUPPORT
-
-void _mdnsFindMQTT() {
- int count = MDNS.queryService("mqtt", "tcp");
- DEBUG_MSG_P(PSTR("[MQTT] MQTT brokers found: %d\n"), count);
- for (int i=0; i<count; i++) {
- DEBUG_MSG_P(PSTR("[MQTT] Broker at %s:%d\n"), MDNS.IP(i).toString().c_str(), MDNS.port(i));
- mqttSetBrokerIfNone(MDNS.IP(i), MDNS.port(i));
- }
-}
-
-#endif
-
 String _mdnsHostname() {
  return getSetting("hostname", getIdentifier());
 }
@@ -46,10 +31,58 @@ void _mdnsServerStart() {
 
 // -----------------------------------------------------------------------------
 
+// 2.7.x and older require MDNS.begin() when interface is UP
+// issue tracker suggest doing begin() for each mode change, but...
+// this does seem to imply pairing it with end() (aka close()),
+// which will completely reset the MDNS object and require a setup once again.
+// this does not seem to work reliably :/ only support STA for the time being
+// 3.0.0 and newer only need to do MDNS.begin() once at setup()
+// however, note that without begin() call it will immediatly crash b/c
+// there are no sanity checks if it was actually called
+constexpr bool MdnsOldCore {
+#if defined(ARDUINO_ESP8266_RELEASE_2_7_2) \
+ || defined(ARDUINO_ESP8266_RELEASE_2_7_3) \
+ || defined(ARDUINO_ESP8266_RELEASE_2_7_4)
+ true
+#else
+ false
+#endif
+};
+
+// As of right now, this needs to be request -> response operation in the same block,
+// so we don't end up using someone else's query results.
+// `queryService()` 3rd arg is timeout, by default it blocks for MDNS_QUERYSERVICES_WAIT_TIME (1000)
+
+// TODO: esp8266 allows async pyzeroconf-like API to have this running independently.
+// In case something other than MQTT needs this, consider extending the API
+// (and notice that RTOS SDK alternative would need to use mdns_query_* ESP-IDF API)
+// TODO: both implementations also have separate queries for A and AAAA records :/
+
+bool mdnsServiceQuery(const String& service, const String& protocol, MdnsServerQueryCallback callback) {
+ bool result { false };
+
+ auto found = MDNS.queryService(service, protocol);
+ for (decltype(found) n = 0; n < found; ++n) {
+ if (callback(MDNS.IP(n).toString(), MDNS.port(n))) {
+ result = true;
+ break;
+ }
+ }
+
+ MDNS.removeQuery();
+
+ return result;
+}
+
+bool mdnsRunning() {
+ return MDNS.isRunning();
+}
+
 void mdnsServerSetup() {
  bool done { false };
-
- MDNS.setHostname(_mdnsHostname());
+ if (!MdnsOldCore) {
+ _mdnsServerStart();
+ }
 
 #if WEB_SUPPORT
  {
@@ -93,29 +126,11 @@ void mdnsServerSetup() {
  MDNS.update();
  });
 
- // 2.7.x and older require MDNS.begin() when interface is UP
- // issue tracker suggest doing begin() for each mode change, but...
- // this does seem to imply pairing it with end() (aka close()),
- // which will completely reset the MDNS object and require a setup once again.
- // this does not seem to work reliably :/ only support STA for the time being
- // 3.0.0 and newer only need to do MDNS.begin() once at setup()
- const static bool OldCore {
- (esp8266::coreVersionNumeric() >= 20702000) && (esp8266::coreVersionNumeric() <= 20703003) };
-
  wifiRegister([](wifi::Event event) {
-#if MQTT_SUPPORT
- if (event == wifi::Event::StationConnected) {
- _mdnsFindMQTT();
- }
-#endif
- if (OldCore && (event == wifi::Event::StationConnected) && !MDNS.isRunning()) {
+ if (MdnsOldCore && (event == wifi::Event::StationConnected) && !MDNS.isRunning()) {
  _mdnsServerStart();
  }
  });
-
- if (!OldCore) {
- _mdnsServerStart();
- }
 }
 
 #endif // MDNS_SERVER_SUPPORT

code/espurna/mdns.h

@@ -10,4 +10,8 @@ Copyright (C) 2017-2019 by Xose Pérez <xose dot perez at gmail dot com>
 
 #include "espurna.h"
 
+using MdnsServerQueryCallback = bool(*)(String&& server, uint16_t port);
+
+bool mdnsRunning();
+bool mdnsServiceQuery(const String& service, const String& protocol, MdnsServerQueryCallback callback);
 void mdnsServerSetup();