Book Image

Hands-On Network Programming with C

By : Lewis Van Winkle
Book Image

Hands-On Network Programming with C

By: Lewis Van Winkle

Overview of this book

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 the 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 have experience of working with client-server applications and be able to implement new network programs in C. 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.
Table of Contents (26 chapters)
Title Page
About Packt

SMTP dialog

SMTP is a text-based TCP protocol that works on port 25. SMTP works in a lock-step, one-at-a-time dialog, with the client sending commands and the server sending responses for each command.

In a typical session, the dialog goes as follows:

  1. The client first establishes a connection to the SMTP server.
  2. The server initiates with a greeting. This greeting indicates that the server is ready to receive commands.
  3. The client then issues its own greeting.
  4. The server responds.
  5. The client sends a command indicating who the mail is from.
  6. The server responds to indicate that the sender is accepted.
  7. The client issues another command, which specifies the mail's recipient.
  8. The server responds indicating the recipient is accepted.
  9. The client then issues a DATA command.
  10. The server responds asking the client to proceed.
  11. The client transfers the email.

The protocol is very simple. In the following example SMTP session, is the client, and the server is (C and S indicate whether...