Socket I/O模型之完成端口

http://tangfeng.javaeye.com/blog/518148

“完成端口”模型是迄今为止最为复杂的一种I/O模型。然而，假若一个应用程序同时需要管理为数众多的套接字，那么采用这种模型，往往可以达到最佳的系统性能！但不幸的是，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！

// 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; }   

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