Add close method to AsyncUDP and improve UDP multicast handler lifecycle management

src/mesh/udp/UdpMulticastHandler.h

@@ -50,14 +50,15 @@ class UdpMulticastHandler final
             return;
         }
         LOG_DEBUG("Stopping UDP multicast");
-#if !defined(ARCH_NRF52)
         udp.close();
-#endif
         isRunning = false;
     }
 
     void onReceive(AsyncUDPPacket packet)
     {
+        if (!isRunning) {
+            return;
+        }
         size_t packetLength = packet.length();
 #if defined(ARCH_NRF52)
         IPAddress ip = packet.remoteIP();
@@ -84,7 +85,7 @@ class UdpMulticastHandler final
 
     bool onSend(const meshtastic_MeshPacket *mp)
     {
-        if (!mp || !udp) {
+        if (!isRunning || !mp || !udp) {
             return false;
         }
 #if defined(ARCH_NRF52)

src/platform/nrf52/AsyncUDP.cpp

@@ -36,6 +36,13 @@ bool AsyncUDP::writeTo(const uint8_t *data, size_t len, IPAddress ip, uint16_t p
     return udp.endPacket();
 }
 
+void AsyncUDP::close()
+{
+    udp.stop();
+    localPort = 0;
+    _onPacket = nullptr;
+}
+
 // AsyncUDPPacket
 AsyncUDPPacket::AsyncUDPPacket(EthernetUDP &source) : _udp(source), _remoteIP(source.remoteIP()), _remotePort(source.remotePort())
 {

src/platform/nrf52/AsyncUDP.h

@@ -22,6 +22,7 @@ class AsyncUDP : public Print, private concurrency::OSThread
 
     bool listenMulticast(IPAddress multicastIP, uint16_t port, uint8_t ttl = 64);
     bool writeTo(const uint8_t *data, size_t len, IPAddress ip, uint16_t port);
+    void close();
 
     size_t write(uint8_t b) override;
     size_t write(const uint8_t *data, size_t len) override;