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Pradeeban Kathiravelu

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Herausgeber: Packt Publishing
Kategorie: Wissenschaft und neue Technologien
Sprache: Englisch

Beschreibung

Discover practical solutions for a wide range of real-world network programming tasks

About This Book

Solve real-world tasks in the area of network programming, system/networking administration, network monitoring, and more.
Familiarize yourself with the fundamentals and functionalities of SDN
Improve your skills to become the next-gen network engineer by learning the various facets of Python programming

Who This Book Is For

This book is for network engineers, system/network administrators, network programmers, and even web application developers who want to solve everyday network-related problems. If you are a novice, you will develop an understanding of the concepts as you progress with this book.

What You Will Learn

Develop TCP/IP networking client/server applications
Administer local machines' IPv4/IPv6 network interfaces
Write multi-purpose efficient web clients for HTTP and HTTPS protocols
Perform remote system administration tasks over Telnet and SSH connections
Interact with popular websites via web services such as XML-RPC, SOAP, and REST APIs
Monitor and analyze major common network security vulnerabilities
Develop Software-Defined Networks with Ryu, OpenDaylight, Floodlight, ONOS, and POX Controllers
Emulate simple and complex networks with Mininet and its extensions for network and systems emulations
Learn to configure and build network systems and Virtual Network Functions (VNF) in heterogeneous deployment environments
Explore various Python modules to program the Internet

In Detail

Python Network Programming Cookbook - Second Edition highlights the major aspects of network programming in Python, starting from writing simple networking clients to developing and deploying complex Software-Defined Networking (SDN) and Network Functions Virtualization (NFV) systems. It creates the building blocks for many practical web and networking applications that rely on various networking protocols. It presents the power and beauty of Python to solve numerous real-world tasks in the area of network programming, network and system administration, network monitoring, and web-application development.

In this edition, you will also be introduced to network modelling to build your own cloud network. You will learn about the concepts and fundamentals of SDN and then extend your network with Mininet. Next, you'll find recipes on Authentication, Authorization, and Accounting (AAA) and open and proprietary SDN approaches and frameworks. You will also learn to configure the Linux Foundation networking ecosystem and deploy and automate your networks with Python in the cloud and the Internet scale.

By the end of this book, you will be able to analyze your network security vulnerabilities using advanced network packet capture and analysis techniques.

Style and approach

This book follows a practical approach and covers major aspects of network programming in Python. It provides hands-on recipes combined with short and concise explanations on code snippets. This book will serve as a supplementary material to develop hands-on skills in any academic course on network programming. This book further elaborates network softwarization, including Software-Defined Networking (SDN), Network Functions Virtualization (NFV), and orchestration. We learn to configure and deploy enterprise network platforms, develop applications on top of them with Python.

Details

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Leseprobe

Python Network Programming Cookbook

Second Edition

Overcome real-world networking challenges

Pradeeban Kathiravelu

Dr. M. O. Faruque Sarker

BIRMINGHAM - MUMBAI

Python Network Programming Cookbook

Second Edition

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the authors, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: March 2014

Second edition: August 2017

Production reference: 1080817

Published by Packt Publishing Ltd.

Livery Place

35 Livery Street

Birmingham

B3 2PB, UK.

ISBN 978-1-78646-399-9

www.packtpub.com

Credits

Authors

Pradeeban Kathiravelu

Dr. M. O. Faruque Sarker

Copy Editors

Safis Editing

Juliana Nair

Reviewers

Dr. S. Gowrishankar

Michael Bright

Project Coordinator

Judie Jose

Commissioning Editor

Kartikey Pandey

Proofreader

Safis Editing

Acquisition Editor

Rahul Nair

Indexer

Aishwarya Gangawane

Content Development Editor

Abhishek Jadhav

Graphics

Kirk D'Penha

Technical Editor

Mohd Riyan Khan

Production Coordinator

Aparna Bhagat

About the Author

Pradeeban Kathiravelu is an open source evangelist. He is a Ph.D. researcher at INESC-ID Lisboa/Instituto Superior Tecnico, Universidade de Lisboa, Portugal, and Universite Catholique de Louvain, Belgium. He is a Fellow of Erasmus Mundus Joint Degree in Distributed Computing (EMJD-DC), researching a software-defined approach to quality of service and data quality in multi-tenant clouds.

Pradeeban holds a master of science degree, Erasmus Mundus European Master in Distributed Computing (EMDC), from Instituto Superior Tecnico, Portugal and KTH Royal Institute of Technology, Sweden. He also holds a first class bachelor of science in engineering (Hons) degree, majoring in computer science and engineering, from the University of Moratuwa, Sri Lanka. His research interests include Software-Defined Networking (SDN), distributed systems, cloud computing, web services, big data in biomedical informatics, Network Functions Virtualizations (NFV), and data mining. He is very interested in free and open source software development and has been an active participant in the Google Summer of Code (GSoC) program since 2009, as a student and as a mentor.

Pradeeban has published several conference papers and co-authored a few book chapters. He has also worked on OpenDaylight Cookbook and LearningOpenDaylight as a technical reviewer. Python NetworkProgramming Cookbook, Second Edition (2017) is his first book as an author, and he is quite excited about it.

I would like to thank my readers for the interest in the book. Please feel free to contact me if you need any assistance in the topics or the recipes, beyond what we have discussed in the book. I would like to thank the entire editorial team at Packt, including Abhishek Jadhav, Rahul Nair, and Mohd Riyan Khan. I would like to extend my thanks to the Linux Foundation for their open source projects on softwarization of networks and systems. I would like to thank my friends and colleagues who helped me in various ways. I would like to thank Prof. Luis Veiga (INESC-ID Lisboa), my MSc and Ph.D. advisor, for sharing his wisdom and encouragement throughout my stay in Instituto Superior Tecnico. I would like to thank him for being my mentor since 2012. I would also like to thank Prof. Ashish Sharma (Emory University, Atlanta) for his guidance and motivation. My special thanks go to my loving wife, Juejing Gu. This book would not be a reality without her continuous support and creative suggestions. Her tireless efforts helped me always be on time without missing the deadlines. I would like to thank my mom, Selvathie Kathiravelu, for her support.

Dr. M. O. Faruque Sarker is a software architect based in London, UK, where he has been shaping various Linux and open source software solutions, mainly on cloud computing platforms, for commercial companies, educational institutions, and multinational consultancies. Over the past 10 years, he has been leading a number of Python software development and cloud infrastructure automation projects. In 2009, he started using Python, where he was responsible for shepherding a fleet of miniature E-puck robots at the University of South Wales, Newport, UK. Later, he honed his Python skills, and he was invited to work on the Google Summer of Code (2009/2010) programs for contributing to the BlueZ and Tahoe-LAFS open source projects. He is the author of Python Network Programming Cookbook and Learning Python Network Programming both by Packt Publishing.

He received his Ph.D. in multi-robot systems from the University of South Wales. He is currently working at University College London. He takes an active interest in cloud computing, software security, intelligent systems, and child-centric education. He lives in East London with his wife, Shahinur, and daughter, Ayesha.

All praises and thanks to Allah, the God who is the Merciful and the Beneficent. I would not be able to finish this book without the help of God.I would like to thank everyone who has contributed to the publication of this book, including the publisher, technical reviewers, editors, my family and friends for their sacrifice of time, encouraging words, and smiles, especially my wife Shahinur Rijuani for her love and support in my work. I also thank the readers who have patiently been waiting for this book and who have given me lots of valuable feedback.

About the Reviewers

Dr. S. Gowrishankar is currently working as an associate professor in the Department of Computer Science and Engineering at Dr. Ambedkar Institute of Technology, Bengaluru, Karnataka, India.

He received his Ph.D. in Engineering from Jadavpur University, Kolkata, West Bengal, India in 2010, MTech in software engineering and BE in computer science and engineering from Visvesvaraya Technological University (VTU), Belagavi, Karnataka, India in the year 2005 and 2003 respectively.

From 2011 to 2014 he worked as a senior research scientist and tech lead at Honeywell Technology Solutions, Bengaluru, Karnataka, India.

He has published several papers in various reputed international journals and conferences. He is serving as an editor and reviewer for various prestigious international journals. He is also a member of IEEE, ACM, CSI, and ISTE.

He has delivered many keynote addresses and invited talks throughout India on a variety of subjects related to computer science and engineering. He was instrumental in organizing several conferences, workshops, and seminars. He has also served on the panel of a number of academic bodies of universities and autonomous colleges as a BOS and BOE member.

His current research interests are mainly focused on data science, including its technical aspects as well as its applications and implications. Specifically, he is interested in the applications of Machine Learning, Data Mining, and Big Data Analytics in Healthcare.

I would like to acknowledge my earnest gratitude to my wife, Roopa K M, for her constant source of support and encouragement throughout this assignment. I'm truly thankful to almighty God for having her in my life and give her my deepest expression of love and appreciation.

Michael Bright, RHCE/RHCSA, is a solution architect working in the HPE EMEA Customer Innovation Center.

He has strong experience across Cloud and Container technologies (Docker, Kubernetes, AWS, GCP, Azure) as well as NFV/SDN.

Based in Grenoble, France, he runs a Python user group and is a co-organizer of the Docker and FOSS Meetup groups. He has a keen interest in Container, Orchestration, and Unikernel technologies on which he has presented and run training tutorials in several conferences. He has presented many times on subjects diverse as NFV, Docker, Container Orchestration, Unikernels, Jupyter Notebooks, MongoDB, and Tmux.

Michael has a wealth of experience across pure research, R&D and pre-sales consulting roles.

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I dedicate this book to the world, in memory of my dad, Kanapathipillai Kathiravelu.

Preface

What this book covers

What you need for this book

Who this book is for

Sections

Getting ready

How to do it…

How it works…

There's more…

Preface

It has been more than 3 years since Python Network Programming Cookbook was first published. In this second edition, we extend our book to discuss the recent advancements in the networking industry and network softwarization. The widespread use of Software-Defined Networking (SDN), Network Functions Virtualization (NFV), and orchestration have been addressed in detail in the latter chapters while the first eight chapters were taken from the first edition, improved with a few new recipes based on the feedback from the readers.

This book is an exploratory guide to network programming in Python. It has touched a wide range of networking protocols such as TCP/UDP, HTTP/HTTPS, FTP, SMTP, POP3, IMAP, and CGI. With the power and interactivity of Python, it brings joy and fun to develop various scripts for performing real-world tasks on network and system administration, web application development, interacting with your local and remote network, low-level network packet capture and analysis, and so on. The primary focus of this book is to give you a hands-on experience on the topics covered. So, this book covers less theory, but it is packed with practical materials.

This book is written with a DevOps mindset, where a developer is also more or less in charge of operation, that is, deploying the application and managing various aspects of it, such as remote server administration, monitoring, scaling-up, and optimizing for better performance. This book introduces you to a bunch of open-source, third-party Python libraries, which are ideal to be used in various use cases. We elaborate in detail the configurations of complex networking systems with helpful hints to ensure that the reader can follow them without getting stuck.

We hope you will enjoy the recipes presented in this book and extend them to make them even more powerful and enjoyable.

What this book covers

Chapter 1, Sockets, IPv4, and Simple Client/Server Programming, introduces you to Python's core networking library with various small tasks and enables you to create your first client-server application.

Chapter 2, Multiplexing Socket I/O for Better Performance, discusses various useful techniques for scaling your client/server applications with default and third-party libraries.

Chapter 3, IPv6, Unix Domain Sockets, and Network Interfaces, focuses more on administering your local machine and looking after your local area network.

Chapter 4, Programming with HTTP for the Internet, enables you to create a mini command-line browser with various features such as submitting web forms, handling cookies, managing partial downloads, compressing data, and serving secure content over HTTPS.

Chapter 5, Email Protocols, FTP, and CGI Programming, brings you the joy of automating your FTP and e-mail tasks such as manipulating your Gmail account, and reading or sending emails from a script or creating a guest book for your web application. We learn to write email clients with SMTP and POP3.

Chapter 6, Programming Across Machine Boundaries, gives you a taste of automating your system administration and deployment tasks over SSH. You can run commands, install packages, or set up new websites remotely from your laptop.

Chapter 7, Working with Web Services - XML-RPC, SOAP, and REST, introduces you to various API protocols such as XML-RPC, SOAP, and REST. You can programmatically ask any website or web service for information and interact with them. For example, you can search for products on Amazon or Google.

Chapter 8, Network Monitoring and Security, introduces you to various techniques for capturing, storing, analyzing, and manipulating network packets. This encourages you to go further to investigate your network security issues using concise Python scripts.

Chapter 9, Network Modeling, introduces you to the world of network simulations and emulations. You learn to simulate networks with NS-3, and emulate networking systems with Mininet and its extensions.

Chapter 10, Getting Started with SDN, discusses the enterprise SDN controllers, configuring them to use in Software-Defined Networks. We learn to develop SDN visually with MiniEdit, and configure the networks with OpenDaylight, ONOS, Floodlight, Ryu, and POX controllers.

Chapter 11, Authentication, Authorization, and Accounting (AAA), introduces how the networks are secured, and discusses configuring LDAP clients with Python, accounting aspects of the network, and authentication and access of network services.

Chapter 12, Open and Proprietary Networking Solutions, discusses in detail, configuring large-scale enterprise networking projects, including a few projects from Cisco, Juniper, VMware, and the Linux Foundation.

Chapter 13, NFV and Orchestration - A Larger Ecosystem, discusses configuring complex NFV and orchestration systems of the Linux Foundation, such as OPNFV, DPDK, SNAS.io, Dronekit, and PNDA. We elaborate the use of Python in these complex systems.

Chapter 14, Programming the Internet, presents you various Python libraries for BGP protocol and implementations developed for the internet scale. We learn to use and benchmark libraries such as exabgp and yabgp, and also discuss the looking glass implementations with Python.

What you need for this book

You need a working PC or laptop, preferably with a modern Linux operating system. The installation instructions are written and tested on Ubuntu 16.04 LTS and would work on any recent Debian-based Linux operating system without modification. We developed for Python 3. However, we have maintained backward-compatibility with Python 2 in our recipes as much as we can. On the other hand, some open source projects used in this book do not yet support Python 3. So, ideally, you will need both Python 2 and Python 3 to test all the recipes in this book.

Most of the recipes in this book will run on other platforms such as Windows and Mac OS with some changes in the configuration steps. Some of the recipes require two or more computers in a cluster to test the distributed systems. You may use Amazon Web Services (AWS) to initiate a cluster inside a single placement group to test these recipes.

You also need a working internet connection to install the third-party software libraries mentioned with respective recipes. If you do not have a stable or continuous internet connection, you can download the third-party libraries and install them in one go. However, it is highly recommended to test some of these recipes with the internet connection, as it would make the configuration task minimal and more interesting, than having to download a bulk of software in bunch. Moreover, testing the application in an AWS cluster would certainly require the internet connectivity.

The following is a list of the Python third-party libraries with their download URLs:

ntplib:

https://pypi.python.org/pypi/ntplib/

diesel:

https://pypi.python.org/pypi/diesel/

nmap:

https://pypi.python.org/pypi/python-nmap

scapy:

https://pypi.python.org/pypi/scapy

netifaces:

https://pypi.python.org/pypi/netifaces/

netaddr:

https://pypi.python.org/pypi/netaddr

pyopenssl:

https://pypi.python.org/pypi/pyOpenSSL

pygeocoder:

https://pypi.python.org/pypi/pygocoder

pyyaml:

https://pypi.python.org/pypi/PyYAML

requests:

https://pypi.python.org/pypi/requests

feedparser:

https://pypi.python.org/pypi/feedparser

paramiko:

https://pypi.python.org/pypi/paramiko/

fabric:

https://pypi.python.org/pypi/Fabric

supervisor:

https://pypi.python.org/pypi/supervisor

xmlrpclib:

https://pypi.python.org/pypi/xmlrpclib

SOAPpy:

https://pypi.python.org/pypi/SOAPpy

bottlenose:

https://pypi.python.org/pypi/bottlenose

construct:

https://pypi.python.org/pypi/construct/

libpcap:

https://pypi.python.org/pypi/pcap

setup tools:

https://pypi.python.org/pypi/setuptools

exabgp:

https://pypi.python.org/pypi/exabgp

traixroute:

https://pypi.python.org/pypi/traixroute

dronekit:

https://pypi.python.org/pypi/dronekit

dronekit-sitl:

https://pypi.python.org/simple/dronekit-sitl/

ryu:

https://pypi.python.org/pypi/ryu

Flask:

https://pypi.python.org/pypi/Flask

smtpd:

https://pypi.python.org/pypi/secure-smtpd

twisted:

https://pypi.python.org/pypi/Twisted

tornado:

https://pypi.python.org/pypi/tornado

dnspython:

https://pypi.python.org/pypi/dnspython

ldap3:

https://pypi.python.org/pypi/ldap3

Eve:

https://pypi.python.org/pypi/Eve

RequestsThrottler:

https://pypi.python.org/pypi/RequestsThrottler

PyNSXv:

https://pypi.python.org/pypi/pynsxv

vmware-nsx:

https://pypi.python.org/pypi/vmware-nsx

Other software needed to run some recipes are as follows:

postfix:

http://www.postfix.org/

openssh server:

http://www.openssh.com/

mysql server:

http://downloads.mysql.com/

apache2:

http://httpd.apache.org/download.cgi/

virtualenv:

https://virtualenv.pypa.io/

filezilla:

https://filezilla-project.org/

vsftpd:

https://security.appspot.com/vsftpd.html

telnetd:

telnetd.sourceforge.net/

curl:

https://curl.haxx.se/

NS-3:

https://www.nsnam.org/ns-3-26/download/

Mininet:

mininet.org/

Ansible:

https://www.ansible.com

Git:

https://git-scm.com/

aptitude:

https://www.openhub.net/p/aptitude

Node-ws / wscat:

https://www.npmjs.com/package/wscat

MaxiNet:

https://github.com/MaxiNet/MaxiNet/

Mininet-WiFi:

https://github.com/intrig-unicamp/mininet-wifi

ContainerNet:

https://github.com/containernet/containernet.git

Ant:

ant.apache.org/

Maven:

https://maven.apache.org/

OpenDaylight:

https://www.opendaylight.org/downloads

ONOS:

https://wiki.onosproject.org/display/ONOS/Downloads

Floodlight:

http://www.projectfloodlight.org/download/

POX:

http://github.com/noxrepo/pox

libnl-3-dev:

https://packages.debian.org/sid/libnl-3-dev

libnl-genl-3-dev:

https://packages.debian.org/sid/libnl-genl-3-dev

libnl-route-3-dev:

https://packages.debian.org/sid/libnl-route-3-dev

pkg-config:

https://www.freedesktop.org/wiki/Software/pkg-config/

python-tz:

pytz.sourceforge.net/

libpcap-dev:

https://packages.debian.org/libpcap-dev

libcap2-dev:

https://packages.debian.org/jessie/libcap2-dev

wireshark:

https://www.wireshark.org/

Juniper Contrail:

http://www.juniper.net/support/downloads/?p=contrail#sw

OpenContrail Controller:

https://github.com/Juniper/contrail-controller

Contrail Server Manager:

https://github.com/Juniper/contrail-server-manager.git

VMWare NSX for vSphere 6.3.2:

https://my.vmware.com/group/vmware/details?downloadGroup=NSXV_632_OSS&productId=417

OPNFV Compass:

https://wiki.opnfv.org/display/compass4nfv/Compass4nfv

OPNFV SDNVPN:

https://wiki.opnfv.org/display/sdnvpn/SDNVPN+project+main+page

libpcap-dev:

https://packages.debian.org/libpcap-dev

DPDK:

http://dpdk.org/download

SNAS.io:

http://www.snas.io/

pnda.io:

http://pnda.io/

bgperf:

https://github.com/pradeeban/bgperf.git

swig:

www.swig.org/

yabgp:

https://github.com/smartbgp/yabgp

Virtualbox:

https://www.virtualbox.org/wiki/VirtualBox

Vagrant:

https://www.vagrantup.com/

RED PNDA:

https://github.com/pndaproject/red-pnda

Apache ZooKeeper:

https://zookeeper.apache.org/

Apache Cassandra:

http://cassandra.apache.org/

RabbitMQ:

https://www.rabbitmq.com/

pyIOSXR:

https://github.com/fooelisa/pyiosxr

Cisco Spark API:

https://github.com/CiscoDevNet/ciscosparkapi

Who this book is for

If you are a network programmer, system/network administrator, or a web application developer, this book is ideal for you. You should have a basic familiarity with the Python programming language and TCP/IP networking concepts. However, if you are a novice, you will develop an understanding of the concepts as you progress with this book. This book will serve as supplementary material for developing hands-on skills in any academic course on network programming.

Sections

In this book, you will find several headings that appear frequently (Getting ready, How to do it…, How it works…, There's more…, and See also). To give clear instructions on how to complete a recipe, we use these sections as follows:

Getting ready

This section tells you what to expect in the recipe, and describes how to set up any software or any preliminary settings required for the recipe.

How to do it…

This section contains the steps required to follow the recipe.

How it works…

This section usually consists of a detailed explanation of what happened in the previous section.

There's more…

This section consists of additional information about the recipe in order to make the reader more knowledgeable about the recipe.

Reader feedback

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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Questions

If you have a problem with any aspect of this book, you can contact us at [email protected], and we will do our best to address the problem.

Sockets, IPv4, and Simple Client/Server Programming

In this chapter, we will cover the following recipes:

Printing your machine's name and IPv4 address

Retrieving a remote machine's IP address

Converting an IPv4 address to different formats

Finding a service name, given the port and protocol

Converting integers to and from host to network byte order

Setting and getting the default socket timeout

Handling socket errors gracefully

Modifying a socket's send/receive buffer size

Changing a socket to the blocking/non-blocking mode

Reusing socket addresses

Printing the current time from the internet time server

Writing an SNTP client

Writing a simple TCP echo client/server application

Writing a simple UDP echo client/server application

Introduction

This chapter introduces Python's core networking library through some simple recipes. Python's socket module has both class-based and instances-based utilities. The difference between a class-based and instance-based method is that the former doesn't need an instance of a socket object. This is a very intuitive approach. For example, in order to print your machine's IP address, you don't need a socket object. Instead, you can just call the socket's class-based methods. On the other hand, if you need to send some data to a server application, it is more intuitive that you create a socket object to perform that explicit operation. The recipes presented in this chapter can be categorized into three groups as follows:

In the first few recipes, the class-based utilities have been used in order to extract some useful information about host, network, and any target service.

After that, some more recipes have been presented using the instance-based utilities. Some common socket tasks, including manipulating the socket timeout, buffer size, and blocking mode has been demonstrated.

Finally, both class-based and instance-based utilities have been used to construct some clients, which perform some practical tasks, for example, synchronizing the machine time with an internet server or writing a generic client/server script.

You can use these demonstrated approaches to write your own client/server application.

Printing your machine's name and IPv4 address

Sometimes, you need to quickly discover some information about your machine, for example, the hostname, IP address, number of network interfaces, and so on. This is very easy to achieve using Python scripts.

Getting ready

You need to install Python on your machine before you start coding. Python comes preinstalled in most of the Linux distributions. For Microsoft Windows operating systems, you can download binaries from the Python website: http://www.python.org/download/.

Currently, Python 3.x is released in addition to Python 2.x. Many of the current Linux distributions and macOS versions are still shipping Python 2 by default. However, some ship both of them.

Download the relevant installer for your operating system and the relevant version based on whether your operating system is 32 bit or 64 bit.

You may consult the documentation of your operating system to check and review your Python setup. After installing Python on your machine, you can try opening the Python interpreter from the command line by typing python. This will show the interpreter prompt, >>>, which should be similar to the following output:

~$ python

Python 2.7.12 (default, Nov 19 2016, 06:48:10)

[GCC 5.4.0 20160609] on linux2

Type "help", "copyright", "credits" or "license" for more information.

>>>

How it works...

The import socket statement imports one of Python's core networking libraries. Then, we use the two utility functions, gethostname() and gethostbyname(host_name). You can type help(socket.gethostname) to see the online help information from within the command line. Alternatively, you can type the following address in your web browser at http://docs.python.org/3/library/socket.html. You can refer to the following code:

gethostname(...) gethostname() -> string Return the current host name. gethostbyname(...) gethostbyname(host) -> address Return the IP address (a string of the form '255.255.255.255') for a host.

The first function takes no parameter and returns the current or localhost name. The second function takes a single hostname parameter and returns its IP address.

Retrieving a remote machine's IP address

Sometimes, you need to translate a machine's hostname into its corresponding IP address, for example, a quick domain name lookup. This recipe introduces a simple function to do that.

Converting an IPv4 address to different formats

When you would like to deal with low-level network functions, sometimes, the usual string notation of IP addresses are not very useful. They need to be converted to the packed 32-bit binary formats.

How it works...

In this recipe, the two IP addresses have been converted from a string to a 32-bit packed format using a for-in statement. Additionally, the Python hexlify function is called from the binascii module. This helps to represent the binary data in a hexadecimal format.

Finding a service name, given the port and protocol

If you would like to discover network services, it may be helpful to determine what network services run on which ports using either the TCP or UDP protocol.

Getting ready

If you know the port number of a network service, you can find the service name using the getservbyport() socket class function from the socket library. You can optionally give the protocol name when calling this function.

How it works...

In this recipe, the for-in statement is used to iterate over a sequence of variables. So for each iteration, we use one IP address to convert them in their packed and unpacked format.

Converting integers to and from host to network byte order

If you ever need to write a low-level network application, it may be necessary to handle the low-level data transmission over the wire between two machines. This operation requires some sort of conversion of data from the native host operating system to the network format and vice versa. This is because each one has its own specific representation of data.

How to do it...

Python's socket library has utilities for converting from a network byte order to host byte order and vice versa. You may want to become familiar with them, for example,

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Python Network Programming Cookbook - Second Edition E-Book

Pradeeban Kathiravelu

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Sockets, IPv4, and Simple Client/Server Programming

Introduction

Printing your machine's name and IPv4 address

Getting ready

How it works...

Retrieving a remote machine's IP address

Converting an IPv4 address to different formats

How it works...

Finding a service name, given the port and protocol

Getting ready

How it works...

Converting integers to and from host to network byte order

How to do it...