UDP

begin()

Initializes the UDP library and network settings.

// SYNTAX
Udp.begin(port);

// PROTOTYPE
uint8_t begin(uint16_t port, network_interface_t nif=0);

If using SYSTEM_THREAD(ENABLED), you'll need to wait until the network is connected before calling Udp.begin(). With Device OS 6.2.0 and later, system thread is always enabled.

If you are listening on a specific port, you need to call begin(port) again every time the network is disconnected and reconnects, as well.

const int LISTENING_PORT = 8080;

#ifndef SYSTEM_VERSION_v620
SYSTEM_THREAD(ENABLED); // System thread defaults to on in 6.2.0 and later and this line is not required
#endif

UDP udp;
bool wasConnected = false;

void setup() {

}

void loop() {
  // For Wi-Fi, use WiFi.ready()
    if (Cellular.ready()) {
        if (!wasConnected) {
            udp.begin(LISTENING_PORT);
            wasConnected = true;
        }
    }
    else {
        wasConnected = false;
    }
}

nif is the network interface to bind to. This is typically omitted, in which case the primary network inteface is used (cellular or Wi-Fi). You can, however pass Ethernet, WiFi, or Cellular as this parameter, which will bind to that specific interface. This is most commonly used when you use cellular as your cloud connection, but listen for UDP packets on Ethernet from an isolated Ethernet LAN.

In Device OS 6.2.0 and later, nif can be Tether to allow UDP to and from another device such as a Raspberry Pi connected by UART serial.