Why pytest hangs while testing simple async function?

I have a simple echo server function. Everything works fine if I launch pytest with a single test, but if I launch it with two tests then the second one hangs on waiting for the server to start, and I can't understand why. Here's a complete code.

The server:

async def handle_echo(reader, writer):
    data = await reader.read(100)

    message = data.decode()
    addr = writer.get_extra_info('peername')
    print(f"SERVER: Received {message!r} from {addr!r}")
    writer.write(data)
    await writer.drain()
    print(f"SERVER: Sent: {message!r}")

    writer.close()
    print("SERVER: Closed the connection")

Test setup:

HOST = "localhost"


@pytest.fixture()
def event_loop():
    return asyncio.get_event_loop()


async def _async_wait_for_server(event_loop, addr, port):
    while True:
        a_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    try:
        await event_loop.sock_connect(a_socket, (addr, port))
        return
    except ConnectionRefusedError:
        await asyncio.sleep(0.001)

    finally:
        a_socket.close()


@pytest.fixture()
def server(event_loop):
    unused_tcp_port = 65432
    cancel_handle = asyncio.ensure_future(main(unused_tcp_port), loop=event_loop)
    event_loop.run_until_complete(asyncio.wait_for(
        _async_wait_for_server(event_loop, HOST, unused_tcp_port), 5.0))
    try:
        yield unused_tcp_port
    finally:
        cancel_handle.cancel()


async def main(port):
    server = await asyncio.start_server(handle_echo, HOST, port)
    addr = server.sockets[0].getsockname()
    print(f'SERVER: Serving on {addr[0:2]}')
    async with server:
        await server.serve_forever()

Tests:

@pytest.mark.asyncio
async def test_something(server):
    message = "Foobar!"
    reader, writer = await asyncio.open_connection(HOST, server)

    print(f'CLIENT: Sent {message!r}')
    writer.write(message.encode())
    await writer.drain()

    data = await reader.read(100)
    print(f'CLIENT: Received {data.decode()!r}')

    print('CLIENT: Close the connection')
    writer.close()
    await writer.wait_closed()

@pytest.mark.asyncio
async def test_another_thing(server):
    # Literally the same

Pytest output: ================================================================== test session starts =================================================================== platform win32 -- Python 3.7.0, pytest-6.2.5, py-1.10.0, pluggy-1.0.0 -- C:\Users\hurrd.virtualenvs\chatServer-iuEQ-ghN\Scripts\python.exe cachedir: .pytest_cache rootdir: C:\Users\hurrd\PycharmProjects\chatServer plugins: asyncio-0.16.0 collected 2 items

tests/unit/test_themes.py::test_something PASSED [ 50%]

tests/unit/test_themes.py::test_another_thing