Before you start reading this book, you should already know the basics of Python programming, such as the basic syntax, variable types, data type tuple, list dictionary, functions, strings, and methods. At the moment of writing this book, versions 3.7.2 and 2.7.15 are available at python.org/downloads. In this book, we will work with version 3.7 for code examples and installing packages.

The examples and source code for this chapter are available in this book's GitHub repository in the Chapter01 folder: https://github.com/PacktPublishing/Learning-Python-Networking-Second-Edition.

This first section offers an introduction to essential networking concepts, with a strong focus on the TCP/IP stack.

The following discussion is based on Internet Protocol version 4 (IPv4). Since the internet has run out of IPv4 addresses, a new version, IPv6, has been developed, which is intended to resolve this situation. However, although IPv6 is being used in a few areas, its deployment is progressing slowly and the majority of the internet will likely be using IPv4 for a while longer. We'll focus on IPv4 in this section, and then we will discuss the relevant changes in the IPv6 section of this chapter.

TCP/IP is a set of protocols that were designed to work...

This section explains concepts regarding IP addresses and ports, network interfaces in a local machine, and other concepts related to protocols, such as Dynamic Host Configuration Protocol (DHCP) and DNS.

IP addresses are addresses that help to uniquely identify a device over the internet. A port is an endpoint for communication in an operating system.

When you connect to the internet, your device is assigned a public IP address, and each website you visit also has a public IP address. So far, we have used IPv4 as an addressing system. The main problem with this is that the internet is running out of IPv4 public address space and so it is necessary...

This section explains concepts regarding the Network Address Translation (NAT) protocol and introduces the differences between the IPv4 and IPv6 formats.

This mechanism makes the traffic from the private network appear to be coming from a single valid public internet address, which effectively hides the private addresses from the internet. If you inspect the output of ip addr or ipconfig/all commands, then you will find that your devices are using private range addresses, which would have been assigned to them by your DHCP server or by your router through DHCP address dynamic assignment.

The private address ranges that are usually assigned are as follows:

• 10.0.0.0 to 10.255.255.255
• 172.16.0.0 to 172.31.255...

In this section, we're going to look at a general approach to network programming in Python. We'll be introducing the main standard library modules and look at some examples to see how they relate to the TCP/IP stack.

The Python Package Index, or PyPI, which can be found at https://pypi.python.org, is the official software repository for third-party applications in the Python programming language. Python developers want it to be a comprehensive catalog of all Python packages written in open source code.

To download packages from the PyPI repository, you can use several tools, but in this section, we will explain how to use...

This section will help you update the basics of Wireshark to capture packets, filter them, and inspect them. You can use Wireshark to analyze the network traffic of a suspicious program, analyze the traffic flow in your network, or solve network problems. We will also review the pyshark module for capturing packets in Python.

Wireshark is a network packet analysis tool that captures packets in real time and displays them in a graphic interface. Wireshark includes filters, color coding, and other features that allow you to analyze network traffic and inspect packets individually.

Wireshark implements a wide range of filters that facilitate the definition of search...

In this chapter, we have completed an introduction to TCP/IP and how machines communicate in a network. We learned about the main protocols of the network stack and the different types of address for communicating in a network. We started with Python libraries for network programming and looked at socket and the urlllib and requests modules, and provided an example of how we can interact and obtain information from RFC documents. We also acquired some basic knowledge so that we are able to perform a network traffic analysis with Wireshark.

Wireshark is provided with innumerable functionalities, thanks to which we will be able to identify and analyze network traffic and identify communications in our network.

In the next chapter, you will learn how to use Python as an HTTP client so that you can make requests over the REST API and retrieve web resources with the urllib...

1. What TCP/IP layer does user interaction with computers and services occur?
2. Why do we need to replace IPv4 with the IPv6 protocol?
3. What protocol allows you to dynamically configure IP addresses in the device's operating system?
4. What mechanism makes the traffic from the private network appear to be coming from a single valid public internet address and hides the private addresses from the internet?
5. What are the main options for installing Python packages on your localhost machine?
6. What is the main Python tool for creating virtual environments, which also includes a separate Python installation for the packages?
7. What are the main modules that we can find in Python to make HTTP requests at a high level?
8. What are the main modules that we can find in Python to make HTTP requests at a low level?
9. Which library can we use to analyze network traffic in Python that Wireshark...

By going to the following links, you will find more information about the tools and the official Python documentation that was mentioned in this chapter:

• This is the official documentation for the socket package: https://docs.python.org/3/library/socket.html
• This is the official documentation for downloading and installing Wireshark: https://www.wireshark.org/
• This is the official documentation for the pyshark package: https://kiminewt.github.io/pyshark/