def select_random_ports(n):
    """Selects and return n random ports that are available."""
    ports = []
    for i in xrange(n):
        sock = socket.socket()
        sock.bind(('', 0))
        while sock.getsockname()[1] in _random_ports:
            sock.close()
            sock = socket.socket()
            sock.bind(('', 0))
        ports.append(sock)
    for i, sock in enumerate(ports):
        port = sock.getsockname()[1]
        sock.close()
        ports[i] = port
        _random_ports.add(port)
    return ports
Selects and return n random ports that are available.