util.py 文件源码

def refusing_port():
    """Returns a local port number that will refuse all connections.

    Return value is (cleanup_func, port); the cleanup function
    must be called to free the port to be reused.
    """
    # On travis-ci, port numbers are reassigned frequently. To avoid
    # collisions with other tests, we use an open client-side socket's
    # ephemeral port number to ensure that nothing can listen on that
    # port.
    server_socket, port = bind_unused_port()
    server_socket.setblocking(1)
    client_socket = socket.socket()
    client_socket.connect(("127.0.0.1", port))
    conn, client_addr = server_socket.accept()
    conn.close()
    server_socket.close()
    return (client_socket.close, client_addr[1])