Important parts of a UDP packet:

• Time to Live (TTL) — How long a packet should live on the network before being discarded.
• Source port — A random (unused) port chosen by the sender.
• Destination port — The port on the receiving end, which normally is determined by the application being used.
• Source address — “From” IP address.
• Destination address — “To” IP address.
• Data — The, well, data.