#include <ESP8266WiFi.h>
#include <WiFiUdp.h>

const char* ssid = "xxxxxxxx";
const char* password = "yyyyyyy";

char * HostName = "192.168.67.141"; // Zieladdr
const uint16_t HostPort = 15731; // Zielport
const uint16_t LocalPort = 15730;

WiFiUDP udp;


bool sendMessage(const byte * data)
{
if(udp.beginPacket(HostName,HostPort))
{
Serial.println("beginPacket ok");
}else
{
Serial.println("beginPacket err");
}

udp.write(data, 13);
Serial.println(" Bytes writen");

if(udp.endPacket())
{
Serial.println("endPacket ok");
}else
{
Serial.println("endPacket err");
}
}

void setup(void)
{
Serial.begin(115200);
Serial.println("");
Serial.println("setup begin");


if (WiFi.mode(WIFI_STA))
{
Serial.println("to AP ok");
} else {
Serial.println("to AP err");
}

while (! WiFi.begin(SSID, PASSWORD))
{
Serial.print(".") ;
yield();
}
Serial.println("WiFi begin ok");

if(WiFi.waitForConnectResult() != WL_CONNECTED)
{
Serial.printf("Could not connect to %s\n", SSID);
while(1) delay(500); // Brutaler Halt
}


while (! udp.begin(LocalPort) )
{
Serial.print("+") ;
yield();
}
Serial.println("UDP ok");
Serial.print("setup end\r\n");
}

void loop(void)
{
static unsigned long timestamp;
byte can1[13] = {0x00, 0x23, 0x03, 0x00, 0x08, 0x00, 0x00, 0x00, 0x01, 0x01, 0x00, 0x00, 0x00}; // Besetzt Sende CAN message Adresse 1 an
byte can2[13] = {0x00, 0x23, 0x03, 0x00, 0x08, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00}; // Besetzt Sende CAN message Adresse 1 aus

//byte can1[13] = {0x00, 0x16, 0x03, 0x00, 0x06, 0x00, 0x00, 0x38, 0x00, 0x01, 0x01, 0x00, 0x00}; // Weichen Befehl Sende CAN message
//byte can2[13] = {0x00, 0x16, 0x03, 0x00, 0x06, 0x00, 0x00, 0x38, 0x00, 0x00, 0x01, 0x00, 0x00}; // Weichen Befehl Sende CAN message

byte can3[13] = {0x00, 0x16, 0x03, 0x00, 0x06, 0x00, 0x00, 0x38, 0x01, 0x01, 0x01, 0x00, 0x00}; // Weichen Befehl Sende CAN message
byte can4[13] = {0x00, 0x16, 0x03, 0x00, 0x06, 0x00, 0x00, 0x38, 0x01, 0x00, 0x01, 0x00, 0x00}; // Weichen Befehl Sende CAN message


if(millis() - timestamp > 10)
{
sendMessage(can1);
timestamp = millis();
delay(10000);
sendMessage(can2);
timestamp = millis();
delay(10000);
sendMessage(can3);
timestamp = millis();
delay(10000);
sendMessage(can4);
timestamp = millis();
delay(10000);
}
}

I am pretty sure this can be made to a throttle as well. I just need to spend more time understanding how to loco control signals are sent, and I guess there could be some differences between DCC, motorola and Mfx. But in your code it looks like you already send loco commands over UDP so you got that figured out. On my layout I am using MS2, so this is why I am sending the signals directly to the control box via CAN.