# Start a server, on ‹localhost›, on the given port (using
# ‹asyncio.start_server›) and have two clients connect to it.  The
# server takes care of the underlying sockets, so we will not be
# creating them manually. Data is, again, transferred as ‹bytes›
# object.

# The server should return whatever data was sent to it. Clients
# should send ‹hello› and ‹world›, respectively, then wait for the
# answer from the server and return this answer. Add ‹print›
# statements to make sure your server and clients behave as
# expected; print data received by the server, sent to the clients
# and sent and received by the clients on the client side. Make sure
# to close the writing side of sockets once data is exhausted.

import asyncio

# Server-side handler for connecting clients. Read the message from
# the client and echo it back to the client.

async def handle_client( reader, writer ):
    pass # print( "server received & sending", ... )

# Client: connect to the server, send a message, wait for the answer
# and return this answer. Assert that the answer matches the message
# sent. Sleep for 1 second after sending ‹world›, to ensure message
# order.

async def client( port, msg ):
    pass # print( "client sending", ... )
    pass # print( "client received", ... )

# Start the server and the two clients, gather the data back from
# the two clients into a list, return this list; starting with the
# ‹hello› client. Use the provided port.

async def start( port ):
    pass

def test_main() -> None:

    import sys
    import random
    from io import StringIO

    stdout = sys.stdout
    out = StringIO()
    sys.stdout = out

    data = asyncio.run( start( random.randint( 9000, 13000 ) ) )
    assert data == ( 'hello', 'world' ), data

    sys.stdout = stdout
    output_ = out.getvalue()
    output = output_.split('\n')

    assert 'client sending hello' in output[ 0 : 3 ], output
    assert 'client sending world' in output[ 0 : 3 ], output
    assert 'server received & sending hello' in \
            output[ 1 : 3 ], output
    assert 'server received & sending world' in \
            output[ 2 : ], output

if __name__ == "__main__":
    test_main()