"""
User Datagram Protocol (TCP/IP protocol stack)
"""
from construct import *
udp_header = Struct("udp_header",
Value("header_length", lambda ctx: 8),
UBInt16("source"),
UBInt16("destination"),
ExprAdapter(UBInt16("payload_length"),
encoder = lambda obj, ctx: obj + 8,
decoder = lambda obj, ctx: obj - 8,
),
UBInt16("checksum"),
)
if __name__ == "__main__":
cap = "0bcc003500280689".decode("hex")
obj = udp_header.parse(cap)
print obj
print repr(udp_header.build(obj))
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