Implementing a network sniffer using Python

Before learning about the implementation of a network sniffer, let's learn about a particular struct method:

• struct.pack(fmt, v1, v2, ...): This method returns a string that contains the values v1, v2, and so on, packed according to the given format
• struct.unpack(fmt, string): This method unpacks the string according to the given format

Let's discuss the code in the following code snippet:

import struct
ms=  struct.pack('hhl', 1, 2, 3)
print (ms)
k= struct.unpack('hhl',ms)
print k

The output for the preceding code is as follows:

G:PythonNetworkingnetwork>python str1.py
 ☻ ♥
(1, 2, 3)

First, import the struct module, and then pack the 1, 2, and 3 integers in the hhl format. The packed values are like machine code. Values are unpacked using the same hhl format; here, h means a short integer and l means a long integer. More details are provided in the subsequent sections.

Consider the situation of the client-server model; let's illustrate it by means of...