What is a socket in Python?

Sockets are a key concept in network programming that allow communication between processes or applications. In Python, sockets are enabled through the socket library.

At a high level, a socket represents an endpoint in a communication channel. Sockets work similarly to file handles, except they facilitate communication over a network rather than with files on your local file system.

When working with sockets in Python, there are a few key concepts:

Client vs Server Sockets

There are two main types of sockets - client sockets and server sockets:

Here is some sample code for a basic client and server socket:

# Client socket
import socket
client = socket.socket() 
client.connect(("127.0.0.1", 8888))

# Server socket  
import socket
server = socket.socket()  
server.bind(("127.0.0.1", 8888))
server.listen() 

Socket Communication

Once a connection is established between a client and server, sockets allow bidirectional communication through sending and receiving data.

The send() and recv() socket methods are used to transmit byte data across the connection. For convenience, you can wrap a socket in a StringIO object to enable text-based communication.

Concurrency

An important capability provided by sockets is handling multiple client connections concurrently with a single server process. This is facilitated in Python by utilizing threading or asynchronous programming.

The key takeaways are that sockets enable communication between processes, function similar to file handles, and allow a server to handle multiple clients simultaneously. Mastering sockets is critical for network and web programming in Python.