Hello world support for UDP broadcasts over the LAN on ESP32

arch/esp32/esp32.ini

@@ -37,6 +37,7 @@ build_flags =
   -DLIBPAX_ARDUINO
   -DLIBPAX_WIFI
   -DLIBPAX_BLE
+  -DHAS_UDP_MULTICAST=1
   ;-DDEBUG_HEAP
 
 lib_deps =

src/main.cpp

@@ -114,6 +114,11 @@ AccelerometerThread *accelerometerThread = nullptr;
 AudioThread *audioThread = nullptr;
 #endif
 
+#ifdef HAS_UDP_MULTICAST
+#include "mesh/udp/UdpMulticastThread.h"
+UdpMulticastThread *udpThread = nullptr;
+#endif
+
 #if defined(TCXO_OPTIONAL)
 float tcxoVoltage = SX126X_DIO3_TCXO_VOLTAGE; // if TCXO is optional, put this here so it can be changed further down.
 #endif
@@ -783,6 +788,11 @@ void setup()
     LOG_DEBUG("Start audio thread");
     audioThread = new AudioThread();
 #endif
+
+#ifdef HAS_UDP_MULTICAST
+    LOG_DEBUG("Start multicast thread");
+    udpThread = new UdpMulticastThread();
+#endif
     service = new MeshService();
     service->init();
 
@@ -1278,4 +1288,4 @@ void loop()
         mainDelay.delay(delayMsec);
     }
 }
-#endif
+#endif

src/main.h

@@ -49,6 +49,11 @@ extern Adafruit_DRV2605 drv;
 extern AudioThread *audioThread;
 #endif
 
+#ifdef HAS_UDP_MULTICAST
+#include "mesh/udp/UdpMulticastThread.h"
+extern UdpMulticastThread *udpThread;
+#endif
+
 // Global Screen singleton.
 extern graphics::Screen *screen;
 

src/mesh/NodeDB.cpp

@@ -299,6 +299,9 @@ NodeDB::NodeDB()
     resetRadioConfig(); // If bogus settings got saved, then fix them
     // nodeDB->LOG_DEBUG("region=%d, NODENUM=0x%x, dbsize=%d", config.lora.region, myNodeInfo.my_node_num, numMeshNodes);
 
+    // Uncomment below to always enable UDP broadcasts
+    // config.network.enabled_protocols = meshtastic_Config_NetworkConfig_ProtocolFlags_UDP_BROADCAST;
+
     // If we are setup to broadcast on the default channel, ensure that the telemetry intervals are coerced to the minimum value
     // of 30 minutes or more
     if (channels.isDefaultChannel(channels.getPrimaryIndex())) {

src/mesh/Router.cpp

@@ -274,6 +274,12 @@ ErrorCode Router::send(meshtastic_MeshPacket *p)
             abortSendAndNak(encodeResult, p);
             return encodeResult; // FIXME - this isn't a valid ErrorCode
         }
+#if HAS_UDP_MULTICAST
+        if (udpThread && isFromUs(p) &&
+            config.network.enabled_protocols & meshtastic_Config_NetworkConfig_ProtocolFlags_UDP_BROADCAST) {
+            udpThread->onSend(const_cast<meshtastic_MeshPacket *>(p));
+        }
+#endif
 #if !MESHTASTIC_EXCLUDE_MQTT
         // Only publish to MQTT if we're the original transmitter of the packet
         if (moduleConfig.mqtt.enabled && isFromUs(p) && mqtt) {
@@ -624,6 +630,12 @@ void Router::handleReceived(meshtastic_MeshPacket *p, RxSource src)
         // After potentially altering it, publish received message to MQTT if we're not the original transmitter of the packet
         if ((decoded || p_encrypted->pki_encrypted) && moduleConfig.mqtt.enabled && !isFromUs(p) && mqtt)
             mqtt->onSend(*p_encrypted, *p, p->channel);
+#endif
+#if HAS_UDP_MULTICAST
+        if ((decoded || p_encrypted->pki_encrypted) && !isFromUs(p) && udpThread &&
+            config.network.enabled_protocols & meshtastic_Config_NetworkConfig_ProtocolFlags_UDP_BROADCAST) {
+            udpThread->onSend(const_cast<meshtastic_MeshPacket *>(p_encrypted));
+        }
 #endif
     }
 

src/mesh/udp/UdpMulticastThread.h

@@ -0,0 +1,70 @@
+#pragma once
+#if HAS_UDP_MULTICAST
+#include "configuration.h"
+#include "main.h"
+#include "mesh/Router.h"
+
+#include <AsyncUDP.h>
+#include <WiFi.h>
+
+#define UDP_MULTICAST_DEFAUL_PORT 4403 // Default port for UDP multicast is same as TCP api server
+#define UDP_MULTICAST_THREAD_INTERVAL_MS 15000
+
+class UdpMulticastThread : public concurrency::OSThread
+{
+  public:
+    UdpMulticastThread() : OSThread("UdpMulticast") { udpIpAddress = IPAddress(224, 0, 0, 69); }
+
+    void start()
+    {
+        if (udp.listenMulticast(udpIpAddress, UDP_MULTICAST_DEFAUL_PORT)) {
+            LOG_DEBUG("UDP Listening on IP: %s", WiFi.localIP().toString().c_str());
+            udp.onPacket([this](AsyncUDPPacket packet) { onReceive(packet); });
+        } else {
+            LOG_DEBUG("Failed to listen on UDP");
+        }
+    }
+
+    void onReceive(AsyncUDPPacket packet)
+    {
+        size_t packetLength = packet.length();
+        LOG_DEBUG("UDP broadcast from: %s, len=%u", packet.remoteIP().toString().c_str(), packetLength);
+        meshtastic_MeshPacket mp;
+        uint8_t bytes[meshtastic_MeshPacket_size]; // Allocate buffer for the data
+        size_t packetSize = packet.readBytes(bytes, packet.length());
+        LOG_DEBUG("Decoding MeshPacket from UDP len=%u", packetSize);
+        bool isPacketDecoded = pb_decode_from_bytes(bytes, packetLength, &meshtastic_MeshPacket_msg, &mp);
+        if (isPacketDecoded && router) {
+            UniquePacketPoolPacket p = packetPool.allocUniqueCopy(mp);
+            // Unset received SNR/RSSI
+            p->rx_snr = 0;
+            p->rx_rssi = 0;
+            router->enqueueReceivedMessage(p.release());
+        }
+    }
+
+    bool onSend(const meshtastic_MeshPacket *mp)
+    {
+        if (!mp || WiFi.status() != WL_CONNECTED) {
+            return false;
+        }
+        LOG_DEBUG("Broadcasting packet over UDP (id=%u)", mp->id);
+        uint8_t buffer[meshtastic_MeshPacket_size];
+        size_t encodedLength = pb_encode_to_bytes(buffer, sizeof(buffer), &meshtastic_MeshPacket_msg, mp);
+        udp.broadcastTo(buffer, encodedLength, UDP_MULTICAST_DEFAUL_PORT);
+        return true;
+    }
+
+  protected:
+    int32_t runOnce() override
+    {
+        canSleep = true;
+        // TODO: Might consider a heartbeat for discovery or keep alive?
+        return UDP_MULTICAST_THREAD_INTERVAL_MS;
+    }
+
+  private:
+    IPAddress udpIpAddress;
+    AsyncUDP udp;
+};
+#endif // ARCH_ESP32

src/mesh/wifi/WiFiAPClient.cpp

@@ -112,6 +112,12 @@ static void onNetworkConnected()
         APStartupComplete = true;
     }
 
+#if HAS_UDP_MULTICAST
+    if (udpThread) {
+        udpThread->start();
+    }
+#endif
+
     // FIXME this is kinda yucky, instead we should just have an observable for 'wifireconnected'
 #ifndef MESHTASTIC_EXCLUDE_MQTT
     if (mqtt)
@@ -437,4 +443,4 @@ uint8_t getWifiDisconnectReason()
 {
     return wifiDisconnectReason;
 }
-#endif
+#endif