Chapter 1, Network Programming and Python, introduces core networking concepts for readers that are new to networking, and also covers how network programming is approached in Python.

Chapter 2, HTTP and Working with the Web, introduces you to the HTTP protocol and covers how we can retrieve and manipulate web content using Python as an HTTP client. We also take a look at the standard library urllib and third-party Requests modules.

Chapter 3, APIs in Action, introduces you to working with web APIs using HTTP. We also cover the XML and JSON data formats, and walk you through developing applications using the Amazon Web Services Simple Storage Service (S3) and Twitter APIs.

Chapter 4, Engaging with E-mails, covers the principle protocols used in sending and receiving e-mails, such as SMTP, POP3, and IMAP, and how to work with them in Python 3.

Chapter 5, Interacting with Remote Systems, guides you through the ways of using Python to connect to servers and performing common administrative tasks, including the execution of shell commands through SSH, file transfers with FTP and SMB, authentication with LDAP, and to monitor systems with SNMP.

Chapter 6, IP and DNS, discusses the details of the Internet Protocol (IP), ways of working with IP in Python, and how to use DNS to resolve hostnames.

Chapter 7, Programming with Sockets, covers using TCP and UDP sockets from Python for writing low-level network applications. We also cover HTTPS and TLS for secure data transport.

Chapter 8, Client and Server Applications, looks at writing client and server programs for socket-based communication. By writing an echo application and a chat application we look at developing basic protocols, framing network data, and compare the multithreading and event-based server architectures.

Chapter 9, Applications for the Web, introduces you to writing web applications in Python. We cover the main approaches, methods of hosting Python web applications, and develop an example application in the Flask microframework.

Appendix, Working with Wireshark, covers packet sniffers, the installation of Wireshark, and how to capture and filter packets using the Wireshark application.

This book is aimed at Python 3. While many of the examples will work in Python 2, you'll get the best experience working through this book with a recent version of Python 3. At the time of writing, the latest version is 3.4.3, and the examples were tested against this.

Though Python 3.4 is the preferred version, all the examples should run on Python 3.1 or later, except for the following:

We're also targeting the Linux operating system, and the assumption is made that you are working on a Linux OS. The examples have been tested on Windows though, and we'll make a note of where there may be differences in the requirements or outcomes.

$ yum install python3

$ mkdir ~/.juju
$ curl https:// bitbucket.org/fsquillace/juju-repo/raw/master/juju- x86_64.tar.gz | tar -xz -C ~/.juju

$ export PATH=~/.juju/opt/juju/bin:$PATH

$ juju -f
$ pacman --sync refresh
$ pacman --sync --sysupgrade
$ pacman --sync python3
$ exit

$ juju

$ python3 
Python 3.4.3 (default, Apr 28 2015, 19:59:08)
[GCC 4.7.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

If you're a Python developer, or system administrator with Python experience, and you're looking forward to take your first step in network programming, then this book is for you. Whether you're working with networks for the first time or looking to enhance your existing networking and Python skills, you will find this book very useful.

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "IP addresses have been assigned to your computer by running the ip addr or ipconfig /all command on Windows."

A block of code is set as follows:

import sys, urllib.request

try:
    rfc_number = int(sys.argv[1])
except (IndexError, ValueError):
    print('Must supply an RFC number as first argument')
    sys.exit(2)

template = 'http://www.ietf.org/rfc/rfc{}.txt'
url = template.format(rfc_number)
rfc_raw = urllib.request.urlopen(url).read()
rfc = rfc_raw.decode()
print(rfc)

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are highlighted:

<body>
...
<div id="content">
<h1>Debian &ldquo;jessie&rdquo; Release Information</h1>
<p>Debian 8.0 was
released October 18th, 2014.
The release included many major
changes, described in
...

Any command-line input or output is written as follows:

$ python RFC_downloader.py 2324 | less

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "We can see there's a list of interfaces below the Start button."

We follow PEP 8 as closely as we can, but we also follow the principle that practicality beats purity, and do deviate in a few areas. Imports are often performed on a single line to save space, and we may not strictly adhere to wrapping conventions do to the nature of printed media; we aim for "readability counts".

We have also chosen to focus on the procedural programming style rather than use object-oriented examples. The reason for this is that it is generally easier for someone familiar with object oriented programming to rework procedural examples into an object oriented format than it is for someone unfamiliar with OOP to do the reverse.

Feedback from our readers is always welcome. Let us know what you think about this book—what you liked or disliked. Reader feedback is important for us as it helps us develop titles that you will really get the most out of.

To send us general feedback, simply e-mail <[email protected]>, and mention the book's title in the subject of your message.

If there is a topic that you have expertise in and you are interested in either writing or contributing to a book, see our author guide at www.packtpub.com/authors.

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