pyasyncore library

Warnings

• breaking The `asyncore` module was removed from the Python standard library starting with Python 3.12. Code relying on `import asyncore` will raise an `ImportError` on Python 3.12 and later.
  Fix: Install `pyasyncore` to restore the `asyncore` module for compatibility: `pip install pyasyncore`.
• gotcha `asyncore` is a legacy module. While `pyasyncore` provides compatibility for older code, for new asynchronous application development, Python's `asyncio` module is the modern and recommended approach.
  Fix: For new projects or significant refactoring, consider migrating to `asyncio` to leverage modern async/await syntax and better ecosystem support.
• gotcha `pyasyncore` is specifically intended to provide `asyncore` for Python 3.12 and newer. Installing it on older Python versions (where `asyncore` is still part of the standard library) may lead to shadowing the built-in module, potentially causing subtle behavioral differences or confusion.
  Fix: Only install and use `pyasyncore` on Python 3.12 or newer, where the standard library `asyncore` is absent.

Install

• pip install pyasyncore Install pyasyncore

Imports

• asyncore

  import asyncore

  The library provides the top-level 'asyncore' module, mimicking the standard library behavior prior to Python 3.12.
• asynchat

  import asynchat

  While 'pyasyncore' primarily backports 'asyncore', the related 'pyasynchat' library (from the same author) backports 'asynchat'.

Quickstart

This quickstart demonstrates a basic `asyncore` echo server. It creates a server that listens on `127.0.0.1:8080` and echoes back any data received from connected clients. Run this script, then connect with `nc 127.0.0.1 8080` in another terminal to test. This example is identical to how `asyncore` would have been used in Python versions prior to 3.12.

import asyncore
import socket

class EchoHandler(asyncore.dispatcher_with_send):
    def handle_read(self):
        data = self.recv(8192)
        if data:
            self.send(data)

class EchoServer(asyncore.dispatcher):
    def __init__(self, host, port):
        asyncore.dispatcher.__init__(self)
        self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
        self.set_reuse_addr()
        self.bind((host, port))
        self.listen(5)
        print(f"Echo server listening on {host}:{port}")

    def handle_accept(self):
        pair = self.accept()
        if pair is not None:
            sock, addr = pair
            print(f"Incoming connection from {repr(addr)}")
            handler = EchoHandler(sock)

if __name__ == "__main__":
    # Note: asyncore is blocking. For a simple example, it runs forever.
    # In a real application, you might run it in a separate thread 
    # or integrate it with other event loops (though this defeats its purpose).
    try:
        server = EchoServer('127.0.0.1', 8080)
        asyncore.loop()
    except KeyboardInterrupt:
        print("\nServer stopped.")