Python Provides Two Levels of Network Services

1. Low-Level Network Services

Python offers basic Socket support, providing access to the full set of BSD Sockets API methods for interacting with the underlying operating system's socket interface.

2. High-Level Network Services

The higher-level SocketServer module simplifies the development of network servers by providing server-centric classes.

What is a Socket?

A Socket is essentially a communication endpoint. Applications use sockets to either make requests over the network or respond to requests, enabling communication between processes on the same machine or across different hosts.

socket() Function

In Python, we create a socket using the socket() function. The syntax is as follows:

socket.socket([family[, type[, proto]]])

• family: The socket family can be either AF_UNIX or AF_INET.

• type: The socket type can be either SOCK_STREAM (for connection-oriented protocols) or SOCK_DGRAM (for connectionless protocols).

• proto: The protocol number is generally set to 0 by default.

Socket Object Methods

Server-Side Socket Methods

Client-Side Socket Methods

General Socket Methods

Example: Server

In the example below, we use the socket module to create a simple server.

#!/usr/bin/python3
# Filename: server.py

import socket
import sys

# Create a socket object
serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# Get the local hostname
host = socket.gethostname()

port = 9999

# Bind the socket to the port
serversocket.bind((host, port))

# Start listening for connections (max 5 connections)
serversocket.listen(5)

while True:
    # Establish a connection with the client
    clientsocket, addr = serversocket.accept()
    
    print("Connection from: %s" % str(addr))
    
    msg = 'Welcome to PMeve!\r\n'
    clientsocket.send(msg.encode('utf-8'))
    clientsocket.close()

Example: Client

Here is a simple client that connects to the server created above.

#!/usr/bin/python3
# Filename: client.py

import socket
import sys

# Create a socket object
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# Get the local hostname
host = socket.gethostname()

# Set the port number
port = 9999

# Connect to the server
s.connect((host, port))

# Receive up to 1024 bytes of data
msg = s.recv(1024)

# Close the connection
s.close()

print(msg.decode('utf-8'))

Running the Server and Client

1. In the first terminal, run the server script:

   $ python3 server.py

2. In a second terminal, run the client script:

   $ python3 client.py

You should see the following message in the client terminal:

Welcome to PMeve!

On the server side, the terminal will output:

Connection from: ('192.168.0.118', 33397)

Python Internet Modules

The table below lists some important Python modules for network programming: