udphdr structure comprises /usr/src/linux/include/linux/udp.h
struct udphdr { __u16 source; __u16 dest; __u16 len; __u16 check; };
udphdr->source
16-bit source port
udphdr->dest
16-bit destination port
udphdr->len
It represents the length of the transmitted datagram, 16
udphdr->check
Checksum