CODEWITHSUNDEEP
pythonpython-3.xudpbitstring
theAlse
theAlse

Reputation: 5747

Pythonic way to represent a UDP package

I am looking for a pythonic way to represent a UDP package consisting of different fields with different length and so.

I saw bitstring, but the process of defining all the fields and their length is quite cumbersome. I probably need to create a class and create a variable for each field and length and also check that they don't get overwritten by larger numbers and so on.

To me that sounds like a job for a library but I could not find one.

Does anyone know of such a library suitable for this task?

Upvotes: 0

Views: 485

Answers (2)

game0ver
game0ver

Reputation: 1290

The first way is to use a "batteries included"-module like:

Now if you want to create a custom packet, two ways to do it are either using scapy to create a new custom protocol, or you can use ctypes and struct like so:

import os
import struct
from ctypes import *

class myUDP(Structure):
    _fields_ = [
        ("sport",  c_ushort),
        ("dport",  c_ushort),
        ("sum",    c_ushort),
        ("len",    c_ushort)
    ]

    def __new__(self, packet=None):
        return self.from_buffer_copy(packet)

    def __init__(self, packet=None):
        # unpack your data, etc...
        self.srcport  = struct.unpack("H",self.sport)

The above is a low-level, simple and as minimal as possible example-representation of the UDP header(untested):

UDP header

Though that can a bit difficult to be used in real-world scenarios, with complicated protocols, since it demands a lot of technical work, error handling etc... in order to be a complete packet decoder.

Upvotes: 1

supl
supl

Reputation: 1

You can use scapy for packet manipulation

from scapy.all import *
packet = IP(src="1.1.1.1", dst="2.2.2.2")/UDP(dport=4321, sport=123)/"payload"
print str(packet)
# output: 'E\x00\x00#\x00\x01\x00\x00@\x11t\xc4\x01\x01\x01\x01\x02\x02\x02\x02\x00{\x10\xe1\x00\x0f+?payload'

Upvotes: 0

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