Hands-On Network Programming with C - Learn socket programming in C and write secure and optimized network code (true pdf)

Description

Network programming enables processes to communicate with each other over a computer network, but it is a complex task that requires programming with multiple libraries and protocols. With its support for third-party libraries and structured documentation, C is an ideal language to write network programs. Complete with step-by-step explanations of essential concepts and practical examples, this C network programming book begins with the fundamentals of Internet Protocol, TCP, and UDP. You’ll explore client-server and peer-to-peer models for information sharing and connectivity with remote computers. The book will also cover HTTP and HTTPS for communicating between your browser and website, and delve into hostname resolution with DNS, which is crucial to the functioning of modern web. As you advance, you’ll gain insights into asynchronous socket programming and streams, and explore debugging and error handling. Finally, you’ll study network monitoring and implement security best practices. By the end of this book, you’ll be ready to overcome challenges in network programming with the powerful C language. The code in this book is compatible with the older C99 version as well as the latest C18 and C++17 standards. You’ll work with robust, reliable, and secure code that is portable across operating systems, including Winsock sockets for Windows and POSIX sockets for Linux and macOS. ===== What you will learn * Uncover cross-platform socket programming APIs * Implement techniques for supporting IPv4 and IPv6 * Understand how TCP and UDP connections work over IP * Discover how hostname resolution and DNS work * Interface with web APIs using HTTP and HTTPS * Explore Simple Mail Transfer Protocol (SMTP) for electronic mail transmission * Apply network programming to the Internet of Things (IoT) ===== Who this book is for If you're a developer or a system administrator who wants to get started with network programming, this book is for you. Basic knowledge of C programming is assumed. ===== Lewis Van Winkle is a software programming consultant, entrepreneur, and founder of a successful IoT company. He has over 20 years of programming experience after publishing his first successful software product at age 12. He has over 15 years of programming experience with the C programming language on a variety of operating systems and platforms. He is active in the open-source community and has published several popular open-source programs and libraries-many of them in C. Today, Lewis spends much of his time consulting, where he loves taking on difficult projects that other programmers have given up on. He specializes in network systems, financial systems, machine learning, and interoperation between different programming languages. Cover Title Page Copyright and Credits Dedication About Packt Contributors Table of Contents Preface Section 1 - Getting Started with Network Programming Chapter 1: Introducing Networks and Protocols Technical requirements The internet and C OSI layer model TCP/IP layer model Data encapsulation Internet Protocol What is an address? Domain names Internet routing Local networks and address translation Subnetting and CIDR Multicast, broadcast, and anycast Port numbers Clients and servers Putting it together What's your address? Listing network adapters from C Listing network adapters on Windows Listing network adapters on Linux and macOS Summary Questions Chapter 2: Getting to Grips with Socket APIs Technical requirements What are sockets? Socket setup Two types of sockets Socket functions Anatomy of a socket program TCP program flow UDP program flow Berkeley sockets versus Winsock sockets Header files Socket data type Invalid sockets Closing sockets Error handling Our first program A motivating example Making it networked Working with IPv6 Supporting both IPv4 and IPv6 Networking with inetd Summary Questions Chapter 3: An In-Depth Overview of TCP Connections Technical requirements Multiplexing TCP connections Polling non-blocking sockets Forking and multithreading The select() function Synchronous multiplexing with select() select() timeout Iterating through an fd_set select() on non-sockets A TCP client TCP client code A TCP server TCP server code Building a chat room Blocking on send() TCP is a stream protocol Summary Questions Chapter 4: Establishing UDP Connections Technical requirements How UDP sockets differ UDP client methods UDP server methods A first UDP client/server A simple UDP server A simple UDP client A UDP server Summary Questions Chapter 5: Hostname Resolution and DNS Technical requirements How hostname resolution works DNS record types DNS security Name/address translation functions Using getaddrinfo() Using getnameinfo() Alternative functions IP lookup example program The DNS protocol DNS message format DNS message header format Question format Answer format Endianness A simple DNS query A DNS query program Printing a DNS message name Printing a DNS message Sending the query Summary Questions Further reading Section 2 - An Overview of Application Layer Protocols Chapter 6: Building a Simple Web Client Technical requirements The HTTP protocol HTTP request types HTTP request format HTTP response format HTTP response codes Response body length What's in a URL Parsing a URL Implementing a web client HTTP POST requests Encoding form data File uploads Summary Questions Further reading Chapter 7: Building a Simple Web Server Technical requirements The HTTP server The server architecture Content types Returning Content-Type from a filename Creating the server socket Multiple connections buffering get_client() drop_client() get_client_address() wait_on_clients() send_400() send_404() serve_resource() The main loop Security and robustness Open source servers Summary Questions Further reading Chapter 8: Making Your Program Send Email Technical requirements Email servers SMTP security Finding an email server SMTP dialog The format of an email A simple SMTP client program Enhanced emails Email file attachments Spam-blocking pitfalls Summary Questions Further reading Section 3 - Understanding Encrypted Protocols and OpenSSL Chapter 9: Loading Secure Web Pages with HTTPS and OpenSSL Technical requirements HTTPS overview Encryption basics Symmetric ciphers Asymmetric ciphers How TLS uses ciphers The TLS protocol Certificates Server name identification OpenSSL Encrypted sockets with OpenSSL Certificates A simple HTTPS client Other examples Summary Questions Further reading Chapter 10: Implementing a Secure Web Server Technical requirements HTTPS and OpenSSL summary Certificates Self-signed certificates with OpenSSL HTTPS server with OpenSSL Time server example A full HTTPS server HTTPS server challenges OpenSSL alternatives Alternatives to TLS Summary Questions Further reading Chapter 11: Establishing SSH Connections with libssh Technical requirements The SSH protocol libssh Testing out libssh Establishing a connection SSH authentication Server authentication Client authentication Executing a remote command Downloading a file Summary Questions Further reading Section 4 - Odds and Ends Chapter 12: Network Monitoring and Security Technical requirements The purpose of network monitoring Testing reachability Checking a route How traceroute works Raw sockets Checking local connections Snooping on connections Deep packet inspection Capturing all network traffic Network security Application security and safety Network-testing etiquette Summary Questions Further reading Chapter 13: Socket Programming Tips and Pitfalls Technical requirements Error handling Obtaining error descriptions TCP socket tips Timeout on connect() TCP flow control and avoiding deadlock Congestion control The Nagle algorithm Delayed acknowledgment Connection tear-down The shutdown() function Preventing address-in-use errors Sending to a disconnected peer Socket's local address Multiplexing with a large number of sockets Summary Questions Chapter 14: Web Programming for the Internet of Things Technical requirements What is the IoT? Connectivity options Wi-Fi Ethernet Cellular Bluetooth IEEE 802.15.4 WPANs Hardware choices Single-board computers Microcontrollers FPGAs External transceivers and modems IoT protocols Firmware updates Ethics of IoT Privacy and data collection End-of-life planning Security Summary Questions Appendix A: Answers to Questions Chapter 1, Introducing Networks and Protocols Chapter 2, Getting to Grips with Socket APIs Chapter 3, An In-Depth Overview of TCP Connections Chapter 4, Establishing UDP Connections Chapter 5, Hostname Resolution and DNS Chapter 6, Building a Simple Web Client Chapter 7, Building a Simple Web Server Chapter 8, Making Your Program Send Email Chapter 9, Loading Secure Web Pages with HTTPS and OpenSSL Chapter 10, Implementing a Secure Web Server Chapter 11, Establishing SSH Connections with libssh Chapter 12, Network Monitoring and Security Chapter 13, Socket Programming Tips and Pitfalls Chapter 14, Web Programming for the Internet of Things Appendix B: Setting Up Your C Compiler on Windows Installing MinGW GCC Installing Git Installing OpenSSL Installing libssh Alternatives Appendix C: Setting Up Your C Compiler on Linux Installing GCC Installing Git Installing OpenSSL Installing libssh Appendix D: Setting Up Your C Compiler on macOS Installing Homebrew and the C compiler Installing OpenSSL Installing libssh Appendix E: Example Programs Code license Code included with this book Chapter 1 – Introducing Networks and Protocols Chapter 2 – Getting to Grips with Socket APIs Chapter 3 – An In-Depth Overview of TCP Connections Chapter 4 – Establishing UDP Connections Chapter 5 – Hostname Resolution and DNS Chapter 6 – Building a Simple Web Client Chapter 7 – Building a Simple Web Server Chapter 8 – Making Your Program Send Email Chapter 9 – Loading Secure Web Pages with HTTPS and OpenSSL Chapter 10 – Implementing a Secure Web Server Chapter 11 – Establishing SSH Connections with libssh Chapter 12 – Network Monitoring and Security Chapter 13 – Socket Programming Tips and Pitfalls Chapter 14 – Web Programming for the Internet of Things Other Book You May Enjoy Index