def __init__(self, package, version):
        """Construct a new requirement.

        :param package: the package name.
        :param version: a semver compatible version specification.
        """
        self.package = package
        self.version = version
        if self.version and not re.match(r"[<=>~]", version[:2]):
            self.version = "=={}".format(self.version)
async def echo_client(loop, client):
    try:
        client.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
    except (OSError, NameError):
        pass

    with client:
        while True:
            data = await loop.sock_recv(client, 1000000)
            if not data:
                break
            await loop.sock_sendall(client, data)
    if PRINT:
        print('Connection closed')