Definition of Sockets

A socket can be defined as a software interface that allows two devices on a network to exchange information. In simple terms, a socket is the "bridge" that connects a software application to a network for sending and receiving data.

How does a socket work?

A socket works together with a network protocol such as TCP (Transmission Control Protocol) or UDP (User Datagram Protocol) to establish connections between two endpoints. This data exchange can be viewed as a conversation:

  • The client (the one initiating the conversation) opens a socket to connect to the server.
  • The server (the one waiting for the conversation) listens on a specific port and accepts incoming connections from clients.

Once the client and the server are connected, they can exchange data in both directions. This is what allows applications like web browsers, online games, or email servers to function.

Types of sockets

There are two main types of sockets used for network communication:

  • Stream sockets (TCP): They use the TCP protocol to ensure a reliable connection. They are ideal when all data needs to arrive in the correct order and without losses. Some examples of use include:

    • Web browsing (HTTP)
    • File transfer (FTP)
    • Email applications (SMTP)

  • Datagram sockets (UDP): They use the UDP protocol, which is faster but does not guarantee delivery or the order of the data. They are useful in applications where speed is more important than accuracy, such as:

    • Real-time multiplayer games
    • Real-time video/audio streaming
    • Network protocols like DNS

Components of a socket

A socket consists of the following elements:

  • IP Address: Identifies the device on the network.
  • Port: Defines the specific service on the device that accepts the connection (for example, HTTP uses port 80).
  • Protocol: Specifies how the data should be transferred (TCP or UDP).

Example:

  • In a TCP-based client-server application, the client can connect to the server using its IP address (e.g., 192.168.1.1) and port (e.g., 8080) to initiate communication.