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);