How to create TCP proxy server with asyncio?

You can combine both the TCP client and server examples from the user documentation.

You then need to connect the streams together using this kind of helper:

async def pipe(reader, writer):
    try:
        while not reader.at_eof():
            writer.write(await reader.read(2048))
    finally:
        writer.close()

Here's a possible client handler:

async def handle_client(local_reader, local_writer):
    try:
        remote_reader, remote_writer = await asyncio.open_connection(
            '127.0.0.1', 8889)
        pipe1 = pipe(local_reader, remote_writer)
        pipe2 = pipe(remote_reader, local_writer)
        await asyncio.gather(pipe1, pipe2)
    finally:
        local_writer.close()

And the server code:

# Create the server
loop = asyncio.get_event_loop()
coro = asyncio.start_server(handle_client, '127.0.0.1', 8888)
server = loop.run_until_complete(coro)

# Serve requests until Ctrl+C is pressed
print('Serving on {}'.format(server.sockets[0].getsockname()))
try:
    loop.run_forever()
except KeyboardInterrupt:
    pass

# Close the server
server.close()
loop.run_until_complete(server.wait_closed())
loop.close()