W5100/Ethernet cannot use socket as UDP after using it as TCP

Using Arduino Networking, Protocols, and Devices
10

Here is yours:

void setup() {
	Serial.begin(9600);
	Ethernet.begin(mac, ip, INADDR_NONE, gateway, subnet);
	delay(500);

	Serial.println("Start!");
// here is where the first socket is assigned:
	server.begin();
	ShowSockStatus();
	timer = millis();
}

Here is mine:

void setup() {
	Serial.begin(9600);

        pinMode(4, OUTPUT);
        digitalWrite(4, HIGH);
        
	Ethernet.begin(mac, ip, INADDR_NONE, gateway, subnet);
	delay(500);

// here is socket #0
	Udp.begin(8888);

	Serial.println("Start!");

// here is socket #1
	server.begin();
	ShowSockStatus();
	timer = millis();
}