Add support for multicast UDP

libraries/ESP8266WiFi/src/WiFiUdp.cpp

@@ -35,6 +35,7 @@ extern "C"
 #include "lwip/opt.h"
 #include "lwip/udp.h"
 #include "lwip/inet.h"
+#include "lwip/igmp.h"
 #include "include/UdpContext.h"
 
 /* Constructor */
@@ -73,6 +74,32 @@ uint8_t WiFiUDP::begin(uint16_t port)
     return (_ctx->listen(addr, port)) ? 1 : 0;
 }
 
+uint8_t WiFiUDP::beginMulticast(IPAddress multicast, uint16_t port)
+{
+    if (_ctx)
+    {
+        _ctx->unref();
+        _ctx = 0;
+    }
+    
+
+    ip_addr_t ifaddr;
+    ifaddr.addr = (uint32_t) WiFi.localIP();
+    ip_addr_t multicast_addr;
+    multicast_addr.addr = (uint32_t) multicast;
+
+    if (igmp_joingroup(&ifaddr, &multicast_addr)!= ERR_OK) {
+        return 0;
+    }
+
+    _ctx = new UdpContext;
+    if (!_ctx->listen(*IP_ADDR_ANY, port)) {
+        return 0;
+    }
+
+    return 1;
+}
+
 /* return number of bytes available in the current packet,
    will return zero if parsePacket hasn't been called yet */
 int WiFiUDP::available() {
@@ -117,6 +144,17 @@ int WiFiUDP::endPacket()
         return 0;
 
     _ctx->send();
+    return 1;
+}
+
+int WiFiUDP::endPacketMulticast(IPAddress ip, uint16_t port)
+{
+    if (!_ctx)
+        return 0;
+    ip_addr_t addr;
+    addr.addr = (uint32_t) ip;
+    _ctx->send(&addr, port);
+    return 1;
 }
 
 size_t WiFiUDP::write(uint8_t byte)

libraries/ESP8266WiFi/src/WiFiUdp.h

@@ -38,8 +38,11 @@ public:
   WiFiUDP& operator=(const WiFiUDP& rhs);
   ~WiFiUDP();
 
+  operator bool() const { return _ctx != 0; }
+
   virtual uint8_t begin(uint16_t port);	// initialize, start listening on specified port. Returns 1 if successful, 0 if there are no sockets available to use
   virtual void stop();  // Finish with the UDP socket
+  uint8_t beginMulticast(IPAddress multicast, uint16_t port); // connect to a multicast group and listen on the given port
 
   // Sending UDP packets
   
@@ -52,6 +55,9 @@ public:
   // Finish off this packet and send it
   // Returns 1 if the packet was sent successfully, 0 if there was an error
   virtual int endPacket();
+  // Send the packet to a multicast address
+  // Returns 1 if the packet was sent successfully, 0 if there was an error
+  int endPacketMulticast(IPAddress ip, uint16_t port);
   // Write a single byte into the packet
   virtual size_t write(uint8_t);
   // Write size bytes from buffer into the packet

libraries/ESP8266WiFi/src/include/UdpContext.h

@@ -194,7 +194,7 @@ public:
         return size;
     }
 
-    void send()
+    void send(ip_addr_t* addr = 0, uint16_t port = 0)
     {
         size_t orig_size = _tx_buf_head->tot_len;
 
@@ -209,7 +209,10 @@ public:
             }
         }
 
-        udp_send(_pcb, _tx_buf_head);
+        if (addr)
+            udp_sendto(_pcb, _tx_buf_head, addr, port);
+        else
+            udp_send(_pcb, _tx_buf_head);
 
         for (pbuf* p = _tx_buf_head; p; p = p->next)
         {