Socket I/O模型之完成端口(completion port)
“完成端口”模型是迄今为止最为复杂的一种I/O模型。然而，假若一 的是，该模型只适用于Windows NT和Windows 2000操作系统。因其设计的复杂性，只有在你的应用程序需要同时管理数百乃至上千个套接字的时候，而且希望随着系统内安装的CPU数量的增多，应用程序的性能也可以线性提升，才应考虑采用“完成端口”模型。要记住的一个基本准则是，假如要为Windows NT或Windows 2000开发高性能的服务器应用，同时希望为大量套接字I/O请求提供服务（Web服务器便是这方面的典型例子），那么I/O完成端口模型便是最佳选择！
使用完成端口模型的服务器端代码：
C++代码
// write by larry
// 2009-8-20
// This is a server using completion port.
#include "stdafx.h"
#include <WINSOCK2.H>
#include <stdio.h>
#pragma comment(lib, "ws2_32.lib")
#define PORT 5150
#define MSGSIZE 1024
typedef enum
{
RECV_POSTED
} OPERATION_TYPE;
typedef struct
{
WSAOVERLAPPED overlap;
WSABUF Buffer;
char szMessage[MSGSIZE];
DWORD NumberOfBytesRecvd;
DWORD Flags;
OPERATION_TYPE OperationType;
} PER_IO_OPERATION_DATA, *LPPER_IO_OPERATION_DATA;
DWORD WINAPI WorkerThread(LPVOID CompletionPortID);
int main(int argc, char* argv[])
{
WSADATA wsaData;
SOCKET sListen, sClient;
SOCKADDR_IN local, client;
DWORD i, dwThreadId;
int iAddrSize = sizeof(SOCKADDR_IN);
HANDLE CompletionPort = INVALID_HANDLE_VALUE;
SYSTEM_INFO sysinfo;
LPPER_IO_OPERATION_DATA lpPerIOData = NULL;
// Initialize windows socket library
WSAStartup(0x0202, &wsaData);
// Create completion port
CompletionPort = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 0);
// Create worker thread
GetSystemInfo(&sysinfo);
for (i = 0; i < sysinfo.dwNumberOfProcessors; i++)
{
CreateThread(NULL, 0, WorkerThread, CompletionPort, 0, &dwThreadId);
}
// Create listening socket
sListen = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
// Bind
local.sin_family = AF_INET;
local.sin_addr.S_un.S_addr = htonl(INADDR_ANY);
local.sin_port = htons(PORT);
bind(sListen, (sockaddr*)&local, sizeof(SOCKADDR_IN));
// Listen
listen(sListen, 3);
while (TRUE)
{
// Accept a connection
sClient = accept(sListen, (sockaddr*)&client, &iAddrSize);
printf("Accepted client:%s:%d\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));
// Associate the newly arrived client socket with completion port
CreateIoCompletionPort((HANDLE)sClient, CompletionPort, (DWORD)sClient, 0);
// Launch an asynchronous operation for new arrived connection
lpPerIOData = (LPPER_IO_OPERATION_DATA)HeapAlloc(
GetProcessHeap(),
HEAP_ZERO_MEMORY,
sizeof(PER_IO_OPERATION_DATA));
lpPerIOData->Buffer.len = MSGSIZE;
lpPerIOData->Buffer.buf = lpPerIOData->szMessage;
lpPerIOData->OperationType = RECV_POSTED;
WSARecv(sClient,
&lpPerIOData->Buffer,
1,
&lpPerIOData->NumberOfBytesRecvd,
&lpPerIOData->Flags,
&lpPerIOData->overlap,
NULL);
}
PostQueuedCompletionStatus(CompletionPort, 0xFFFFFFFF, 0, NULL);
CloseHandle(CompletionPort);
closesocket(sListen);
WSACleanup();
return 0;
}
DWORD WINAPI WorkerThread(LPVOID CompletionPortID)
{
HANDLE CompletionPort = (HANDLE)CompletionPortID;
DWORD dwBytesTransferred;
SOCKET sClient;
LPPER_IO_OPERATION_DATA lpPerIOData = NULL;
while (TRUE)
{
GetQueuedCompletionStatus(
CompletionPort,
&dwBytesTransferred,
(DWORD*)&sClient,
(LPOVERLAPPED*)&lpPerIOData,
INFINITE);
if (dwBytesTransferred == 0xFFFFFFFF)
{
return 0;
}
if (lpPerIOData->OperationType == RECV_POSTED)
{
if (dwBytesTransferred == 0)
{
// Connection was closed by client
closesocket(sClient);
HeapFree(GetProcessHeap(), 0, lpPerIOData);
}
else
{
lpPerIOData->szMessage[dwBytesTransferred] = '\0';
send(sClient, lpPerIOData->szMessage, dwBytesTransferred, 0);
// Launch another asynchronous operation for sClient
memset(lpPerIOData, 0, sizeof(PER_IO_OPERATION_DATA));
lpPerIOData->Buffer.len = MSGSIZE;
lpPerIOData->Buffer.buf = lpPerIOData->szMessage;
lpPerIOData->OperationType = RECV_POSTED;
WSARecv(sClient,
&lpPerIOData->Buffer,
1,
&lpPerIOData->NumberOfBytesRecvd,
&lpPerIOData->Flags,
&lpPerIOData->overlap,
NULL);
}
}
}
return 0;
}
// writeby larry
//2009-8-20
// Thisis a server using completion port.
#include"stdafx.h"
#include<WINSOCK2.H>
#include<stdio.h>
#pragmacomment(lib, "ws2_32.lib")
#definePORT 5150
#defineMSGSIZE 1024
typedefenum
{
RECV_POSTED
}OPERATION_TYPE;
typedefstruct
{
WSAOVERLAPPED overlap;
WSABUF Buffer;
char szMessage[MSGSIZE];
DWORD NumberOfBytesRecvd;
DWORD Flags;
OPERATION_TYPE OperationType;
}PER_IO_OPERATION_DATA, *LPPER_IO_OPERATION_DATA;
DWORDWINAPI WorkerThread(LPVOID CompletionPortID);
intmain(int argc, char* argv[])
{
WSADATA wsaData;
SOCKET sListen, sClient;
SOCKADDR_IN local, client;
DWORD i, dwThreadId;
int iAddrSize = sizeof(SOCKADDR_IN);
HANDLE CompletionPort = INVALID_HANDLE_VALUE;
SYSTEM_INFO sysinfo;
LPPER_IO_OPERATION_DATA lpPerIOData = NULL;
// Initialize windows socket library
WSAStartup(0x0202, &wsaData);
// Create completion port
CompletionPort =CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 0);
// Create worker thread
GetSystemInfo(&sysinfo);
for (i = 0; i < sysinfo.dwNumberOfProcessors;i++)
{
CreateThread(NULL, 0, WorkerThread,CompletionPort, 0, &dwThreadId);
}
// Create listening socket
sListen = socket(AF_INET, SOCK_STREAM,IPPROTO_TCP);
// Bind
local.sin_family = AF_INET;
local.sin_addr.S_un.S_addr =htonl(INADDR_ANY);
local.sin_port = htons(PORT);
bind(sListen, (sockaddr*)&local,sizeof(SOCKADDR_IN));
// Listen
listen(sListen, 3);
while (TRUE)
{
// Accept a connection
sClient = accept(sListen,(sockaddr*)&client, &iAddrSize);
printf("Accepted client:%s:%d\n",inet_ntoa(client.sin_addr), ntohs(client.sin_port));
// Associate the newly arrived clientsocket with completion port
CreateIoCompletionPort((HANDLE)sClient,CompletionPort, (DWORD)sClient, 0);
// Launch an asynchronous operation fornew arrived connection
lpPerIOData =(LPPER_IO_OPERATION_DATA)HeapAlloc(
GetProcessHeap(),
HEAP_ZERO_MEMORY,
sizeof(PER_IO_OPERATION_DATA));
lpPerIOData->Buffer.len = MSGSIZE;
lpPerIOData->Buffer.buf =lpPerIOData->szMessage;
lpPerIOData->OperationType =RECV_POSTED;
WSARecv(sClient,
&lpPerIOData->Buffer,
1,
&lpPerIOData->NumberOfBytesRecvd,
&lpPerIOData->Flags,
&lpPerIOData->overlap,
NULL);
}
PostQueuedCompletionStatus(CompletionPort,0xFFFFFFFF, 0, NULL);
CloseHandle(CompletionPort);
closesocket(sListen);
WSACleanup();
return 0;
}
DWORDWINAPI WorkerThread(LPVOID CompletionPortID)
{
HANDLE CompletionPort =(HANDLE)CompletionPortID;
DWORD dwBytesTransferred;
SOCKET sClient;
LPPER_IO_OPERATION_DATA lpPerIOData = NULL;
while (TRUE)
{
GetQueuedCompletionStatus(
CompletionPort,
&dwBytesTransferred,
(DWORD*)&sClient,
(LPOVERLAPPED*)&lpPerIOData,
INFINITE);
if (dwBytesTransferred == 0xFFFFFFFF)
{
return 0;
}
if (lpPerIOData->OperationType == RECV_POSTED)
{
if (dwBytesTransferred == 0)
{
// Connection was closed by client
closesocket(sClient);
HeapFree(GetProcessHeap(), 0,lpPerIOData);
}
else
{
lpPerIOData->szMessage[dwBytesTransferred]= '\0';
send(sClient, lpPerIOData->szMessage,dwBytesTransferred, 0);
// Launch another asynchronousoperation for sClient
memset(lpPerIOData, 0,sizeof(PER_IO_OPERATION_DATA));
lpPerIOData->Buffer.len =MSGSIZE;
lpPerIOData->Buffer.buf =lpPerIOData->szMessage;
lpPerIOData->OperationType =RECV_POSTED;
WSARecv(sClient,
&lpPerIOData->Buffer,
1,
&lpPerIOData->NumberOfBytesRecvd,
&lpPerIOData->Flags,
&lpPerIOData->overlap,
NULL);
}
}
}
return 0;
}
服务器端得主要流程：
1.创建完成端口对象
2.创建工作者线程（这里工作者线程的数量是按照CPU的个数来决定的，这样可以达到最佳性能）
3.创建监听套接字，绑定，监听，然后程序进入循环
4.在循环中，我做了以下几件事情：
(1).接受一个客户端连接
(2).将该客户端套接字与完成端口绑定到一起(还是调用CreateIoCompletionPort，但这次的作用不同)，注意，按道理来讲，此时传递给CreateIoCompletionPort的第三个参数应该是一个完成键，一般来讲，程序都是传递一个单句柄数据结构的地址，该单句柄数据包含了和该客户端连接有关的信息，由于我们只关心套接字句柄，所以直接将套接字句柄作为完成键传递；
(3).触发一个WSARecv异步调用，这次又用到了“尾随数据”，使接收数据所用的缓冲区紧跟在WSAOVERLAPPED对象之后，此外，还有操作类型等重要信息。
在工作者线程的循环中，我们
1.调用GetQueuedCompletionStatus取得本次I/O的相关信息（例如套接字句柄、传送的字节数、单I/O数据结构的地址等等）
2.通过单I/O数据结构找到接收数据缓冲区，然后将数据原封不动的发送到客户端
3.再次触发一个WSARecv异步操作