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

Chapter 11, Establishing SSH Connections with libssh

  1. What is a significant downside of using Telnet?

Essentially, Telnet provides no security features. Passwords are sent as plaintext.

  1. Which port does SSH typically run on?

SSH's official port is TCP port 22. In practice, it is common to run SSH on arbitrary ports in an attempt to hide from attackers. With a properly secured server, these attackers are a nuisance rather than a legitimate threat.

  1. Why is it essential that the client authenticates the SSH server?

If the client doesn't verify the SSH server's identity, then it could be tricked into sending credentials to an impostor.

  1. How is the server typically authenticated?

SSH servers typically use certificates to identity themselves. This is similar to how servers are authenticated when using HTTPS.

  1. How is the SSH client typically authenticated?

It is still common for clients to authenticate with a password. The downside to this method is that if a client is somehow tricked into connecting to an impostor server, then their password will be compromised. SSH provides alternate methods, including authenticating clients using certificates, that aren't susceptible to replay attacks.