Python sockets

Python provides several modules to perform networking tasks. Some of the commonly used modules for networking in Python are:

socket: This module provides low-level networking interface for sending and receiving data across network connections.

http.client: This module provides a high-level HTTP client interface to perform HTTP requests.

urllib: This module provides a higher-level interface for accessing URLs, including handling of cookies, authentication, and redirections.

ftplib: This module provides a high-level FTP client interface to perform FTP operations.

imaplib: This module provides a high-level IMAP client interface to perform IMAP operations.

Python Networking with the socket Module

1. Setting Up a TCP Server and Client

import socket

# Define server host and port
HOST = '127.0.0.1'  # localhost
PORT = 65432        # non-privileged port

# Create a TCP socket
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as server_socket:
    server_socket.bind((HOST, PORT))
    server_socket.listen()
    print(f"Server started and listening on {HOST}:{PORT}")
    
    # Accept connection
    conn, addr = server_socket.accept()
    with conn:
        print(f"Connected by {addr}")
        # Receive data
        data = conn.recv(1024)
        if data:
            print("Received data from client:", data.decode())
            conn.sendall(data)  # Echo back the data

Server Output:

Server started and listening on 127.0.0.1:65432
Connected by ('127.0.0.1', )
Received data from client: Hello, Server!

import socket

HOST = '127.0.0.1'  # The server's hostname or IP address
PORT = 65432        # The port used by the server

# Create a TCP client socket
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as client_socket:
    client_socket.connect((HOST, PORT))
    # Send data
    client_socket.sendall(b"Hello, Server!")
    # Receive data
    data = client_socket.recv(1024)
    print("Received response from server:", data.decode())

Client Output:

Received response from server: Hello, Server!

2. Setting Up a UDP Server and Client

import socket

HOST = '127.0.0.1'  # localhost
PORT = 65433        # non-privileged port

# Create a UDP socket
with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as server_socket:
    server_socket.bind((HOST, PORT))
    print(f"UDP Server started on {HOST}:{PORT}")
    
    # Receive data
    data, addr = server_socket.recvfrom(1024)
    print("Received data from client:", data.decode())
    # Send response
    server_socket.sendto(b"Hello, UDP Client!", addr)

UDP Server Output:

UDP Server started on 127.0.0.1:65433
Received data from client: Hello, UDP Server!

import socket

HOST = '127.0.0.1'  # The server's hostname or IP address
PORT = 65433        # The port used by the server

# Create a UDP client socket
with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as client_socket:
    # Send data
    client_socket.sendto(b"Hello, UDP Server!", (HOST, PORT))
    # Receive response
    data, server = client_socket.recvfrom(1024)
    print("Received response from server:", data.decode())

UDP Client Output:

Received response from server: Hello, UDP Client!

3. Error Handling in Sockets

import socket

try:
    # Attempt to connect to an invalid server
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as client_socket:
        client_socket.connect(("256.256.256.256", 65432))  # Invalid IP
except socket.error as e:
    print("Socket error occurred:", e)

Output:

Socket error occurred: [Errno -2] Name or service not known

4. Setting a Timeout on Sockets

import socket

HOST = '127.0.0.1'  # Localhost
PORT = 65432        # Port to connect to

# Create a TCP socket
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as client_socket:
    # Set a timeout
    client_socket.settimeout(5)  # 5 seconds
    try:
        client_socket.connect((HOST, PORT))
        client_socket.sendall(b"Hello with timeout")
        data = client_socket.recv(1024)
        print("Received:", data.decode())
    except socket.timeout:
        print("Connection timed out")

Output (if server doesn't respond in time):

Connection timed out

5. Socket Options and Configurations

import socket

HOST = '127.0.0.1'
PORT = 65432

# Create a TCP socket
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as server_socket:
    # Allow reuse of the address
    server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    server_socket.bind((HOST, PORT))
    server_socket.listen()
    print(f"Server is listening on {HOST}:{PORT}")

Output:

Server is listening on 127.0.0.1:65432

6. Sending and Receiving Data in Chunks

import socket

HOST = '127.0.0.1'
PORT = 65432

# Server code to receive data in chunks
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as server_socket:
    server_socket.bind((HOST, PORT))
    server_socket.listen()
    conn, addr = server_socket.accept()
    with conn:
        print(f"Connected by {addr}")
        while True:
            data = conn.recv(1024)
            if not data:
                break
            print("Received chunk:", data.decode())

Server Output (receives data in 1 KB chunks):

Connected by ('127.0.0.1', )
Received chunk: This is a large data stream...

Summary