    [StructLayout(LayoutKind.Explicit, Size = 4)]
    public struct in_addr
    {
        [FieldOffset(0)]
        public byte s_b1;
        [FieldOffset(1)]
        public byte s_b2;
        [FieldOffset(2)]
        public byte s_b3;
        [FieldOffset(3)]
        public byte s_b4;

        [FieldOffset(0)]
        public ushort s_w1;
        [FieldOffset(2)]
        public ushort s_w2;

        [FieldOffset(0)]
        public uint S_addr;

        /// <summary>
        /// can be used for most tcp & ip code
        /// </summary>
        public uint s_addr { get { return S_addr; } }

        /// <summary>
        /// host on imp
        /// </summary>
        public byte s_host { get { return s_b2; } }

        /// <summary>
        /// network
        /// </summary>
        public byte s_net { get { return s_b1; } }

        /// <summary>
        /// imp
        /// </summary>
        public ushort s_imp { get { return s_w2; } }

        /// <summary>
        /// imp #
        /// </summary>
        public byte s_impno { get { return s_b4; } }

        /// <summary>
        /// logical host
        /// </summary>
        public byte s_lh { get { return s_b3; } }
    }
    [StructLayout(LayoutKind.Sequential)]
    public struct sockaddr_in
    {
        public ADDRESS_FAMILIES sin_family;
        public ushort sin_port;
        public in_addr sin_addr;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 8)]
        public byte[] sin_zero;
    }