Modern Python Standard Library Cookbook

How to do it...

The steps for this recipe are as follows:

1. Given a file that contains a dump of a TCP packet (on my computer, I saved it as /tmp/packet.dump), we can try to read it as binary data and parse its contents.

The Python struct module is the perfect tool for reading binary-structured data and we can use it to parse our TCP packet as we know the size of each piece:

>>> import struct
>>> with open('/tmp/packet.dump', 'rb') as f:
...     data = struct.unpack_from('>HHLL', f.read())
>>> data
(50291, 80, 2778997212, 644363807)

Being an HTTP connection, the result is what we would expect: Source Port: 50291, Destination Port: 80, Sequence Number: 2778997212, and Acknowledgment Number: 644363807.

2. The same can be done to write back the binary ...