Problem with code for sending UDP packets

I don't see any code to set Udp.remoteIP() or Udp.remotePort().

You have to call UDP.parsePacket() first:

If you are not responding to a received packet then you should probably use something like:

IPAddress destinationIP(192, 168, 1, 177);  // Address of target machine
unsigned int destinationPort = 6555;      // Port to send to


    Udp.beginPacket(destinationIP, destinationPort);