MQTT Last Will and Testament

Register a message with the MQTT broker to publish if the client
loses connection. Also publish online/offline status - all to a
`status` topic.

Author: ckuethe

Diff for: RX_FSK/src/conn-mqtt.cpp

@@ -36,7 +36,7 @@ TimerHandle_t mqttReconnectTimer;
 
 extern t_wifi_state wifi_state;
 char time_str[32];
-
+char lwt[128];
 
 /* Global initalization (on TTGO startup) */
 void MQTT::init() {
@@ -64,16 +64,20 @@ void MQTT::netsetup() {
 
     mqttClient.setServer(ip, sonde.config.mqtt.port);
     snprintf(clientID, 20, "%s%04d", sonde.config.mqtt.id, (int)random(0, 1000));
+    snprintf(lwt, sizeof(lwt), "%sstatus", sonde.config.mqtt.prefix);
     clientID[20] = 0;
     LOG_I(TAG, "pubsub client %s connecting to %s\n", clientID, sonde.config.mqtt.host);
     mqttClient.setClientId(clientID);
     if (strlen(sonde.config.mqtt.password) > 0) {
         mqttClient.setCredentials(sonde.config.mqtt.username, sonde.config.mqtt.password);
     }
+    mqttClient.setWill(lwt, MQTT_QOS, MQTT_RETAIN_TRUE, "lost connection");
+
     MQTT::connectToMqtt();
 }
 
 void MQTT::netshutdown() {
+    mqttClient.publish(lwt, MQTT_QOS, MQTT_RETAIN_TRUE, "offline");
     mqttClient.disconnect(false);  // nice shutdown....
     delay(200);
     mqttClient.disconnect(true);  // force
@@ -91,6 +95,7 @@ void MQTT::updateStation( PosInfo *pi ) {
     unsigned long now = millis();
     if ( (lastMqttUptime == 0) || (now - lastMqttUptime >= sonde.config.mqtt.report_interval) ) {
       MQTT::connectToMqtt();
+      mqttClient.publish(lwt, MQTT_QOS, MQTT_RETAIN_TRUE, "online");
       publishUptime();
       publishPmuInfo();
       publishGps();
@@ -115,6 +120,7 @@ int MQTT::connectToMqtt() {
     return 0;
   LOG_D(TAG, "MQTT not connected, connecting....");
   mqttClient.connect();
+  mqttClient.publish(lwt, MQTT_QOS, MQTT_RETAIN_TRUE, "online");
   return 1;
 }
 
@@ -160,7 +166,7 @@ void MQTT::publishUptime()
     LOG_D(TAG, "publishUptime: sending %s\n", payload);
     char topic[128];
     snprintf(topic, 128, "%s%s", sonde.config.mqtt.prefix, "uptime");
-    mqttClient.publish(topic, 1, 1, payload);
+    mqttClient.publish(topic, MQTT_QOS, MQTT_RETAIN_TRUE, payload);
 }
 
 void MQTT::publishPmuInfo()
@@ -187,7 +193,7 @@ void MQTT::publishPmuInfo()
 
     char topic[128];
     snprintf(topic, sizeof(topic), "%s%s", sonde.config.mqtt.prefix, "pmu");
-    mqttClient.publish(topic, 1, 1, payload);
+    mqttClient.publish(topic, MQTT_QOS, MQTT_RETAIN_TRUE, payload);
 }
 
 
@@ -209,7 +215,7 @@ void MQTT::publishGps()
 
     char topic[128];
     snprintf(topic, sizeof(topic), "%s%s", sonde.config.mqtt.prefix, "gps");
-    mqttClient.publish(topic, 1, 1, payload);
+    mqttClient.publish(topic, MQTT_QOS, MQTT_RETAIN_TRUE, payload);
 }
 
 
@@ -225,7 +231,7 @@ void MQTT::publishPeak(double pf, int rssi)
 
     char topic[128];
     snprintf(topic, sizeof(topic), "%s%s", sonde.config.mqtt.prefix, "spectrum");
-    mqttClient.publish(topic, 1, /* retain */ false, payload);
+    mqttClient.publish(topic, MQTT_QOS_NONE, MQTT_RETAIN_FALSE, payload);
 }
 
 // What's the scanner looking at?
@@ -243,7 +249,7 @@ void MQTT::publishQRG(int num, const char* type, char* launchsite, float mhz)
 
     char topic[128];
     snprintf(topic, sizeof(topic), "%s%s", sonde.config.mqtt.prefix, "qrg");
-    mqttClient.publish(topic, 1, /*retain*/ false, payload);
+    mqttClient.publish(topic, MQTT_QOS_NONE, MQTT_RETAIN_FALSE, payload);
 }
 
 
@@ -257,7 +263,7 @@ void MQTT::publishDebug(char *debugmsg)
     snprintf(payload, 256, "{\"msg\": %s}", debugmsg);
     char topic[128];
     snprintf(topic, sizeof(topic), "%s%s", sonde.config.mqtt.prefix, "debug");
-    mqttClient.publish(topic, 1, /*retain*/ false, payload);
+    mqttClient.publish(topic, MQTT_QOS_NONE, MQTT_RETAIN_FALSE, payload);
 }
 
 void MQTT::publishPacket(SondeInfo *si)
@@ -279,7 +285,7 @@ void MQTT::publishPacket(SondeInfo *si)
     char topic[128];
     snprintf(topic, 128, "%s%s", sonde.config.mqtt.prefix, "packet");
     LOG_D(TAG, "publishPacket: %s\n", payload);
-    mqttClient.publish(topic, 1, 1, payload);
+    mqttClient.publish(topic, MQTT_QOS, MQTT_RETAIN_TRUE, payload);
 }
 
 String MQTT::getStatus() {

Diff for: RX_FSK/src/conn-mqtt.h

@@ -17,6 +17,11 @@
 #define MQTT_SEND_DEBUG 0x80
 #define MQTT_SEND_ANY (MQTT_SEND_UPTIME|MQTT_SEND_SONDE|MQTT_SEND_PMU|MQTT_SEND_GPS|MQTT_SEND_RFINFO|MQTT_SEND_DEBUG)
 
+#define MQTT_QOS_NONE 0
+#define MQTT_QOS 1
+#define MQTT_RETAIN_TRUE true
+#define MQTT_RETAIN_FALSE false
+
 class MQTT : public Conn
 {
 public:

Diff for: RX_FSK/version.h

@@ -1,4 +1,4 @@
 const char *version_name = "rdzTTGOsonde";
-const char *version_id = "dev20241229";
+const char *version_id = "dev20250102";
 const int FS_MAJOR=3;
 const int FS_MINOR=3;