Understanding Sockets

Introduction

Sockets are a way to enable inter-process communication between programs running on a server, or between programs running on separate servers. Communication between servers relies on network sockets, which use the Internet Protocol (IP) to encapsulate and handle sending and receiving data.

Network sockets on both clients and servers are referred to by their socket address. An address is a unique combination of a transport protocol like the Transmission Control Protocol (TCP) or User Datagram Protocol (UDP), an IP address, and a port number.

In this tutorial you will learn about the following different types of sockets that are used for inter-process communication:

• Stream sockets, which use TCP as their underlying transport protocol
• Datagram sockets, which use UDP as their underlying transport protocol
• Unix Domain Sockets, which use local files to send and receive data instead of network interfaces and IP packets.

In each section of this tutorial you will also learn how to enumerate the respective socket types on a Linux system. You’ll examine each type of socket using a variety of command line tools.