public void SetSocketKeepAliveValues(TcpClient tcpc, int KeepAliveTime, int KeepAliveInterval)
{
//KeepAliveTime: default value is 2hr
//KeepAliveInterval: default value is 1s and Detect 5 times
uint dummy = 0; //lenth = 4
byte[] inOptionValues = new byte[System.Runtime.InteropServices.Marshal.SizeOf(dummy) * 3]; //size = lenth * 3 = 12
bool OnOff = true;
BitConverter.GetBytes((uint)(OnOff ? 1 : 0)).CopyTo(inOptionValues, 0);
BitConverter.GetBytes((uint)KeepAliveTime).CopyTo(inOptionValues, Marshal.SizeOf(dummy));
BitConverter.GetBytes((uint)KeepAliveInterval).CopyTo(inOptionValues, Marshal.SizeOf(dummy) * 2);
// of course there are other ways to marshal up this byte array, this is just one way
// call WSAIoctl via IOControl
// .net 1.1 type
//int SIO_KEEPALIVE_VALS = -1744830460; //(or 0x98000004)
//socket.IOControl(SIO_KEEPALIVE_VALS, inOptionValues, null);
// .net 3.5 type
tcpc.Client.IOControl(IOControlCode.KeepAliveValues, inOptionValues, null);
}