Mastering Python Async IO with FastAPI

import selectors

import socket



# Create a selectors object, equivalent to the implementation of epoll, when running on Linux

sel = selectors.DefaultSelector()



# Request reception event handling function. Accept new connections and register read events

def accept(sock, mask):

    conn, addr = sock.accept()  # Accept the connection

    print('Accepted connection from', addr)

    conn.setblocking(False)

    sel.register(conn, selectors.EVENT_READ, read)  # Register the read event



# Request reading event handling function. Read request data and send an HTTP response, then close the connection.

def read(conn, mask):

    data = conn.recv(100)  # Read data from the connection

    print('response to')

    response = "HTTP/1.1 200 OK\r\n" \

            "Content-Type: application/json\r\n" \

            "Content-Length: 18\r\n" \

            "Connection: close\r\n" \

            "\r\n" \

            "{\"Hello": \"World\"}"

    conn.send(response.encode())  # Echo the data

    print('Closing connection')

    sel.unregister(conn)  # Unregister the event

    conn.close()  # Close the connection



# Create a server socket

sock = socket.socket()

sock.bind(('localhost', 8000))

sock.listen()

sock.setblocking(False)



# Register the accept event

sel.register(sock, selectors.EVENT_READ, accept)



print("Server is running on port 8000...")



# Event loop

while True:

    # This will block when there are no requests

    events = sel.select()  # Select the file descriptors (events) that are ready

    print("events length: ", len(events))

    for key, mask in events:

        callback = key.data  # Get the event handling function

        print("handler_name:", callback.__name__)

        callback(key.fileobj, mask)  # Call the event handling function

Server is running on port 8000...

events length:  1

handler_name: accept

Accepted connection from ('127.0.0.1', 60941)

events length:  1

handler_name: read

response to

Closing connection

import socket

from datetime import datetime



# Create a TCP socket

server_socket = socket.socket()



# Bind the socket to the specified IP address and port number

server_socket.bind(('127.0.0.1', 8001))



# Start listening for incoming connections

server_socket.listen(5)



# Loop to accept client connections

while True:

    print("%s Waiting for a connection..." % datetime.now())

    client_socket, addr = server_socket.accept() # This will block, waiting for client connections

    print(f"{datetime.now()} Got connection from {addr}")



    # Receive client data

    data = client_socket.recv(1024)

    print(f"Received: {data.decode()}")



    # Send response data

    response = "HTTP/1.1 200 OK\r\n" \

               "Content-Type: application/json\r\n" \

               "Content-Length: 18\r\n" \

               "Connection: close\r\n" \

               "\r\n" \

               "{\"Hello": \"World\"}"



    client_socket.sendall(response.encode())



    # Close the client socket

    client_socket.close()

2024-12-27 12:53:36.711732 Waiting for a connection...

2024-12-27 12:54:30.715928 Got connection from ('127.0.0.1', 64361)

Received: GET / HTTP/1.1

Host: 127.0.0.1:8001

User-Agent: curl/8.4.0

Accept: */*