proxy.py

#!/usr/bin/env python3

# Simple TCP proxy server
# 
# This script can be used to route traffic from one host to another.
#
# Example:
# proxy.py 127.0.0.1 8080 example.org 80
#
# Running the command above will start a TCP server listening on 127.0.0.1:8080.
# When a client connects to it, it will start a connection to example.org:80, and
# proxy the data from the client to the target, and from the target back to the client.

import asyncio
import sys

script_path, local_address, local_port, remote_address, remote_port = sys.argv

async def proxy(reader, writer):
    while True:
        data = await reader.read(1024)
        
        if not data:
            break

        writer.write(data)
        await writer.drain()

    writer.close()

async def handle_connection(source_reader, source_writer):
    target_reader, target_writer = await asyncio.open_connection(remote_address, remote_port)
    await asyncio.wait([proxy(source_reader, target_writer), proxy(target_reader, source_writer)])

loop = asyncio.get_event_loop()
coro = asyncio.start_server(handle_connection, local_address, local_port, loop=loop)
server = loop.run_until_complete(coro)

try:
    loop.run_forever()
except KeyboardInterrupt:
    pass

server.close()
loop.run_until_complete(server.wait_closed())
loop.close()