我们采用的是I/O Complete Port（以下简称IOCP）处理机制。
简单的讲，当服务应用程序初始化时，它应该先创建一个I/O CP。我们在请求到来后，将得到的数据打包用PostQueuedCompletionStatus发送到IOCP中。这时需要创建一些个线程(7个线程/每CPU，再多就没有意义了)来处理发送到IOCP端口的消息。实现步骤大致如下：
1先在主线程中调用CreateIoCompletionPort创建IOCP。
CreateIoCompletionPort的前三个参数只在把设备同Complete Port相关联时才有用。
此时我们只需传递INVALID_HANDLE_VALUE,NULL和0即可。
第四个参数告诉端口同时能运行的最多线程数，这里设置为0，表示默认为当前计算机的CPU数目。
2我们的ThreadFun线程函数执行一些初始化之后，将进入一个循环，该循环会在服务进程终止时才结束。
在循环中，调用GetQueuedCompletionStatus，这样就把当前线程的ID放入一个等待线程队列中，I/O CP内核对象就总能知道哪个线程在等待处理完成的I/O请求。
如果在IDLE_THREAD_TIMEOUT规定的时间内I/O CP上还没有出现一个Completion Packet，则转入下一次循环。在这里我们设置的IDLE_THREAD_TIMEOUT为1秒。
当端口的I/O完成队列中出现一项时，完成端口就唤醒等待线程队列中的这个线程，该线程将得到完成的I/O项中的信息： 传输的字节数、完成键和OVERLAPPED结构的地址。
在我们的程序中可以用智能指针或者BSTR或者int来接受这个OVERLAPPED结构的地址的值，从而得到消息；然后在这个线程中处理消息。
GetQueuedCompletionStatus的第一个参数hCompletionPort指出了要监视哪一个端口，这里我们传送先前从CreateIoCompletionPort返回的端口句柄。
需要注意的是：
第一， 线程池的数目是有限制的，和CPU数目有关系。
第二， IOCP是一种较为完美的睡眠/唤醒 线程机制；线程当前没有任务要处理时，就进入睡眠状态，从而不占用CPU资源，直到被内核唤醒；
第三， 最近一次刚执行完的线程，下次任务来的时候还会唤醒它；所以有可能比较少被调用的线程以后被调用的几率也少。
测试代码：
using System;
using System.Threading; // Included for the Thread.Sleep call
using Continuum.Threading;
using System.Runtime.InteropServices;
namespace IOCPDemo
{
//=============================================================================
/**////
Sample class for the threading class public class UtilThreadingSample
{
//*****************************************************************************
/**////
Test Method static void Main()
{
// Create the MSSQL IOCP Thread Pool
IOCPThreadPool pThreadPool = new IOCPThreadPool(0, 10, 20, new IOCPThreadPool.USER_FUNCTION(IOCPThreadFunction));
//for(int i =1;i<10000;i++)
{
pThreadPool.PostEvent(1234);
}
Thread.Sleep(100);
pThreadPool.Dispose();
}
//********************************************************************
/**////
Function to be called by the IOCP thread pool. Called when
/// a command is posted for processing by the SocketManager ///
The value provided by the thread posting the event
static public void IOCPThreadFunction(int iValue)
{
try
{
Console.WriteLine("Value: {0}", iValue.ToString());
Thread.Sleep(3000);
}
catch (Exception pException)
{
Console.WriteLine(pException.Message);
}
}
}
}
类代码：
using System;
using System.Threading;
using System.Runtime.InteropServices;
namespace IOCPThreading
{
[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
public sealed class IOCPThreadPool
{
[DllImport("Kernel32", CharSet=CharSet.Auto)]
private unsafe static extern UInt32 CreateIoCompletionPort(UInt32 hFile, UInt32 hExistingCompletionPort, UInt32* puiCompletionKey, UInt32 uiNumberOfConcurrentThreads);
[DllImport("Kernel32", CharSet=CharSet.Auto)]
private unsafe static extern Boolean CloseHandle(UInt32 hObject);
[DllImport("Kernel32", CharSet=CharSet.Auto)]
private unsafe static extern Boolean PostQueuedCompletionStatus(UInt32 hCompletionPort, UInt32 uiSizeOfArgument, UInt32* puiUserArg, System.Threading.NativeOverlapped* pOverlapped);
[DllImport("Kernel32", CharSet=CharSet.Auto)]
private unsafe static extern Boolean GetQueuedCompletionStatus(UInt32 hCompletionPort, UInt32* pSizeOfArgument, UInt32* puiUserArg, System.Threading.NativeOverlapped** ppOverlapped, UInt32 uiMilliseconds);
private const UInt32 INVALID_HANDLE_VALUE = 0xffffffff;
private const UInt32 INIFINITE = 0xffffffff;
private const Int32 SHUTDOWN_IOCPTHREAD = 0x7fffffff;
public delegate void USER_FUNCTION(int iValue);
private UInt32 m_hHandle;
private UInt32 GetHandle { get { return m_hHandle; } set { m_hHandle = value; } }
private Int32 m_uiMaxConcurrency;
private Int32 GetMaxConcurrency { get { return m_uiMaxConcurrency; } set { m_uiMaxConcurrency = value; } }
private Int32 m_iMinThreadsInPool;
private Int32 GetMinThreadsInPool { get { return m_iMinThreadsInPool; } set { m_iMinThreadsInPool = value; } }
private Int32 m_iMaxThreadsInPool;
private Int32 GetMaxThreadsInPool { get { return m_iMaxThreadsInPool; } set { m_iMaxThreadsInPool = value; } }
private Object m_pCriticalSection;
private Object GetCriticalSection { get { return m_pCriticalSection; } set { m_pCriticalSection = value; } }
private USER_FUNCTION m_pfnUserFunction;
private USER_FUNCTION GetUserFunction { get { return m_pfnUserFunction; } set { m_pfnUserFunction = value; } }
private Boolean m_bDisposeFlag;
/**////
SimType: Flag to indicate if the class is disposing private Boolean IsDisposed { get { return m_bDisposeFlag; } set { m_bDisposeFlag = value; } }
private Int32 m_iCurThreadsInPool;
/**////
SimType: The current number of threads in the thread pool public Int32 GetCurThreadsInPool { get { return m_iCurThreadsInPool; } set { m_iCurThreadsInPool = value; } }
/**////
SimType: Increment current number of threads in the thread pool private Int32 IncCurThreadsInPool() { return Interlocked.Increment(ref m_iCurThreadsInPool); }
/**////
SimType: Decrement current number of threads in the thread pool private Int32 DecCurThreadsInPool() { return Interlocked.Decrement(ref m_iCurThreadsInPool); }
private Int32 m_iActThreadsInPool;
/**////
SimType: The current number of active threads in the thread pool public Int32 GetActThreadsInPool { get { return m_iActThreadsInPool; } set { m_iActThreadsInPool = value; } }
/**////
SimType: Increment current number of active threads in the thread pool
