X11Client.cs

private unsafe Task Write(void* ptr, int size)
{
    var p = (byte*)ptr;
    var buf = new byte[size];
    for (var i = 0; i < buf.Length; i++)
        buf[i] = p[i];

    return this._stream.WriteAsync(buf, 0, size);
}

private async Task SetupConnection()
{
    var setupData = new ClientSetupData()
    {
        ByteOrder = BitConverter.IsLittleEndian ? (byte)0x6c : (byte)0x42,
        ProtocolMajorVersion = 11,
        ProtocolMinorVersion = 0,
        LengthOfAuthorizationProtocolName = 0,
        LengthOfAuthorizationProtocolData = 0,
    };
    Task t;
    unsafe
    {
        t = this.Write(&setupData, sizeof(ClientSetupData));
    }
    await t.ConfigureAwait(false);

    throw new NotImplementedException();
}

[StructLayout(LayoutKind.Explicit, Pack = 1, Size = 12)]
private struct ClientSetupData
{
    [FieldOffset(0)]
    public byte ByteOrder;
    [FieldOffset(2)]
    public ushort ProtocolMajorVersion;
    [FieldOffset(4)]
    public ushort ProtocolMinorVersion;
    [FieldOffset(6)]
    public ushort LengthOfAuthorizationProtocolName;
    [FieldOffset(8)]
    public ushort LengthOfAuthorizationProtocolData;
}