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.