🔌 Python Socket Programming – TCP/UDP Client Server with Code

🧲 Introduction – Why Learn Socket Programming?

Socket programming allows Python applications to communicate over the network using standard protocols like TCP and UDP. Whether you’re building a chat app, web server, or IoT communication system, understanding sockets gives you low-level control over how data is sent and received.

🎯 In this guide, you’ll learn:

• What sockets are in networking
• How to create a client-server app in Python
• Differences between TCP and UDP sockets
• Real-world examples and best practices

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✅ What Is a Socket?

A socket is a software endpoint that establishes bidirectional communication between processes across a network.

In Python, the socket module provides low-level networking interfaces for working with TCP/IP and UDP sockets.

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📦 Python socket Module Overview

import socket

Common Constants:

• socket.AF_INET: IPv4
• socket.SOCK_STREAM: TCP
• socket.SOCK_DGRAM: UDP

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🔁 TCP Socket Programming – Client & Server

🖥️ TCP Server Example

import socket

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(('localhost', 12345))
server.listen(1)

print("Server listening on port 12345...")

conn, addr = server.accept()
print(f"Connected to {addr}")

data = conn.recv(1024).decode()
print("Received:", data)
conn.send("Hello from server!".encode())

conn.close()
server.close()

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💻 TCP Client Example

import socket

client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client.connect(('localhost', 12345))

client.send("Hello from client".encode())
response = client.recv(1024).decode()
print("Server says:", response)

client.close()

✅ Output:

Server listening on port 12345...  
Connected to ('127.0.0.1', 60000)  
Received: Hello from client  
Server says: Hello from server!

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📡 UDP Socket Programming – Client & Server

🖥️ UDP Server Example

import socket

server = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
server.bind(('localhost', 12345))

print("UDP server listening...")

data, addr = server.recvfrom(1024)
print("Received:", data.decode())
server.sendto("ACK from server".encode(), addr)

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💻 UDP Client Example

import socket

client = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
client.sendto("Ping from client".encode(), ('localhost', 12345))
data, _ = client.recvfrom(1024)
print("Server says:", data.decode())

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🧰 Real-World Use Cases

Application Type	Socket Type	Example
Chat Application	TCP	Bi-directional messaging
Online Game	UDP	Low-latency position updates
Web Server	TCP	HTTP over TCP
IoT Communication	UDP/TCP	Sensors and actuators
Remote Shell	TCP	CLI over network

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🧠 TCP vs UDP in Socket Programming

Feature	TCP	UDP
Type	Connection-oriented	Connectionless
Speed	Slower, reliable	Faster, no guarantee
Order Guarantee	✅ Yes	❌ No
Use Cases	File transfer, chat apps, APIs	Streaming, DNS, games

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🔐 Best Practices for Socket Programming

✅ Do This	❌ Avoid This
Use try-except for error handling	Assuming the network is always available
Close sockets with socket.close()	Leaving sockets open
Use threads or asyncio for multiple clients	Blocking server with a single client
Set timeouts with socket.settimeout()	Waiting indefinitely on reads
Validate incoming data	Trusting client blindly

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📌 Summary – Recap & Next Steps

Python’s socket module enables you to create both client and server applications using TCP and UDP. It’s perfect for learning how data flows between machines and forms the base for web servers, chat systems, API clients, and more.

🔍 Key Takeaways:

• ✅ Use the socket module for low-level network communication
• ✅ Choose TCP for reliability, UDP for speed
• ✅ Understand bind(), listen(), accept(), connect(), send(), recv()
• ✅ Always handle network errors and close sockets properly

⚙️ Real-World Relevance:
Socket programming is used in web servers, peer-to-peer systems, real-time games, and IoT.

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❓ FAQ – Python Socket Programming

❓ What is a socket in Python?

✅ A socket is a software endpoint used to send/receive data across networks using TCP/IP or UDP.

❓ What’s the difference between TCP and UDP in sockets?

✅ TCP is reliable and ordered.
✅ UDP is faster but does not guarantee delivery or order.

❓ Do I need to install any library?

✅ No. Python’s socket module is built-in.

❓ How do I handle multiple clients in a socket server?

✅ Use threading, multiprocessing, or asyncio to handle multiple clients concurrently.

❓ Can I use sockets with localhost?

✅ Yes! Use 'localhost' or '127.0.0.1' for testing on your own machine.

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