Windows7发送Broadcast，XP无法获取到

如题，同一段代码，XP->XP可行，XP->Win7可行，Win7->Win7可行，Win7->Xp无效。是我本地环境问题吗？有谁碰到了没？Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Broadcast, true);
IPEndPoint ipPoint = new IPEndPoint(IPAddress.Broadcast, ConstPort);
socket.SendTo(bytes, 0, bytes.Length, SocketFlags.None, ipPoint );