Methods and properties described further down are specific to ESP8266. They are not covered in Arduino WiFi library documentation. Before they are fully documented please refer to information below.
uint8_t beginMulticast (IPAddress interfaceAddr, IPAddress multicast, uint16_t port) virtual int beginPacketMulticast (IPAddress multicastAddress, uint16_t port, IPAddress interfaceAddress, int ttl=1) IPAddress destinationIP () uint16_t localPort ()
WiFiUDP class supports sending and receiving multicast packets on STA interface. When sending a multicast packet, replace
udp.beginPacket(addr, port) with
udp.beginPacketMulticast(addr, port, WiFi.localIP()). When listening to multicast packets, replace
udp.beginMulticast(WiFi.localIP(), multicast_ip_addr, port). You can use
udp.destinationIP() to tell whether the packet received was sent to the multicast or unicast address.
For code samples please refer to separate section with examples dedicated specifically to the UDP Class.