Udp.beginMulticast(WiFi.localIP(), multicast_ip_addr, port). When listening to multicast packets, replace udp.begin(port) with Udp.beginPacketMulticast(addr, port, WiFi.localIP()). When sending a multicast packet, replace udp.beginPacket(addr, port) with WiFiUDP class supports sending and receiving multicast packets on STA interface.WiFi.printDiag(Serial) will print out some diagnostic info.WiFi.localIP() is for STA, WiFi.softAPIP() is for AP.WiFi.macAddress(mac) is for STA, WiFi.softAPmacAddress(mac) is for AP.call WiFi.softAP(ssid, password) to set up a WPA2-PSK network (password should be at least 8 characters).
This is mostly similar to WiFi shield library.
