SocketLayerExtensions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Sockets;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace RexStudios.CsharpExtensions
{
    public static class SocketLayerExtensions
    {
        /// <summary>
        /// Using IOControl code to configue socket KeepAliveValues for line disconnection detection(because default is toooo slow) 
        /// https://www.extensionmethod.net/csharp/net/setsocketkeepalivevalues
        /// </summary>
        /// <param name="tcpc">TcpClient</param>
        /// <param name="KeepAliveTime">The keep alive time. (ms)</param>
        /// <param name="KeepAliveInterval">The keep alive interval. (ms)</param>
        public static void SetSocketKeepAliveValues(this 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);
        }
    }
}