Socket I/O模型之选择(select)

在windows平台构建网络应用，必须了解socket I/O模型。windows提供了选择(select)、异步选择(WSAAsyncSelect)、事件选择(WSAEventSelect)、重叠I /O(overlapped I/O)和完成端口(completion port)。

一、客户端代码

C++代码  

1. #include "stdafx.h"  
2. #include <WINSOCK2.H>  
3. #include <stdio.h>  
4. #pragma comment(lib, "ws2_32.lib")  
5. #define SERVER_ADDRESS  "192.168.10.56"  
6. #define PORT  5150  
7. #define MSGSIZE  1024  
8. int main(int argc, char* argv[])  
9. {  
10.     WSADATA wsaData;  
11.     SOCKET sClient;  
12.     SOCKADDR_IN server;  
13.     char szMessage[MSGSIZE];  
14.     int ret;  
15.     // Initialize windows socket library  
16.     WSAStartup(0x0202, &wsaData);  
17.     // Create client socket  
18.     sClient = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);  
19.     // Connect to server  
20.     memset(&server, 0, sizeof(SOCKADDR_IN));  
21.     server.sin_family = AF_INET;  
22.     server.sin_addr.S_un.S_addr = inet_addr(SERVER_ADDRESS);  
23.     server.sin_port = htons(PORT);  
24.     connect(sClient, (sockaddr*)&server, sizeof(SOCKADDR_IN));  
25.     while (TRUE)   
26.     {  
27.         printf("Send:");  
28.         gets(szMessage);  
29.         // Send message  
30.         send(sClient, szMessage, strlen(szMessage), 0);  
31.         // Receive message  
32.         ret = recv(sClient, szMessage, MSGSIZE, 0);  
33.         szMessage[ret] = '\0';  
34.         printf("Received [%d bytes]: '%s'\n", ret, szMessage);  
35.     }  
36.     // Clean up  
37.     closesocket(sClient);  
38.     WSACleanup();  
39.     return 0;  
40. }  

#include "stdafx.h"#include <WINSOCK2.H>#include <stdio.h>#pragma comment(lib, "ws2_32.lib")#define SERVER_ADDRESS  "192.168.10.56"#define PORT  5150#define MSGSIZE  1024int main(int argc, char* argv[]){WSADATA wsaData;SOCKET sClient;SOCKADDR_IN server;char szMessage[MSGSIZE];int ret;// Initialize windows socket libraryWSAStartup(0x0202, &wsaData);// Create client socketsClient = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);// Connect to servermemset(&server, 0, sizeof(SOCKADDR_IN));server.sin_family = AF_INET;server.sin_addr.S_un.S_addr = inet_addr(SERVER_ADDRESS);server.sin_port = htons(PORT);connect(sClient, (sockaddr*)&server, sizeof(SOCKADDR_IN));while (TRUE) {printf("Send:");gets(szMessage);// Send messagesend(sClient, szMessage, strlen(szMessage), 0);// Receive messageret = recv(sClient, szMessage, MSGSIZE, 0);szMessage[ret] = '\0';printf("Received [%d bytes]: '%s'\n", ret, szMessage);}// Clean upclosesocket(sClient);WSACleanup();return 0;}

这是一个最简单的客户端代码，负责发送数据，然后接受返回。

二、使用select模型的服务器

C++代码  

1. // write by larry  
2. // 2009-8-20  
3. // This is server using select model.  
4. #include "stdafx.h"  
5. #include <winsock.h>  
6. #include <stdio.h>  
7. #define PORT  5150  
8. #define MSGSIZE  1024  
9. #pragma comment(lib, "ws2_32.lib")  
10. int g_iTotalConn = 0;  
11. SOCKET g_CliSocketArr[FD_SETSIZE];  
12. DWORD WINAPI WorkerThread(LPVOID lpParam);  
13. int main(int argc, char* argv[])  
14. {  
15.     WSADATA wsaData;  
16.     SOCKET sListen, sClient;  
17.     SOCKADDR_IN local, client;  
18.     int iAddrSize = sizeof(SOCKADDR_IN);  
19.     DWORD dwThreadId;  
20.     // Initialize windows socket library  
21.     WSAStartup(0x0202, &wsaData);  
22.     // Create listening socket  
23.     sListen = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);  
24.     // Bind  
25.     local.sin_family = AF_INET;  
26.     local.sin_addr.S_un.S_addr = htonl(INADDR_ANY);  
27.     local.sin_port = htons(PORT);  
28.     bind(sListen, (sockaddr*)&local, sizeof(SOCKADDR_IN));  
29.     // Listen  
30.     listen(sListen, 3);  
31.     // Create worker thread  
32.     CreateThread(NULL, 0, WorkerThread, NULL, 0, &dwThreadId);  
33.     while (TRUE)   
34.     {  
35.         // Accept a connection  
36.         sClient = accept(sListen, (sockaddr*)&client, &iAddrSize);  
37.         printf("Accepted client:%s:%d\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));  
38.         // Add socket to g_CliSocketArr  
39.         g_CliSocketArr[g_iTotalConn++] = sClient;  
40.     }  
41.     return 0;  
42. }  
43. DWORD WINAPI WorkerThread(LPVOID lpParam)  
44. {  
45.     int i;  
46.     fd_set fdread;  
47.     int ret;  
48.     struct timeval tv = {1, 0};  
49.     char szMessage[MSGSIZE];  
50.     while (TRUE)   
51.     {  
52.         FD_ZERO(&fdread);  
53.         for (i = 0; i < g_iTotalConn; i++)   
54.         {  
55.             FD_SET(g_CliSocketArr[i], &fdread);  
56.         }  
57.         // We only care read event  
58.         ret = select(0, &fdread, NULL, NULL, &tv);  
59.         if (ret == 0)   
60.         {  
61.             // Time expired  
62.             continue;  
63.         }  
64.         for (i = 0; i < g_iTotalConn; i++)   
65.         {  
66.             if (FD_ISSET(g_CliSocketArr[i], &fdread))   
67.             {  
68.                 // A read event happened on g_CliSocketArr  
69.                 ret = recv(g_CliSocketArr[i], szMessage, MSGSIZE, 0);  
70.                 if (ret == 0 || (ret == SOCKET_ERROR && WSAGetLastError() == WSAECONNRESET))   
71.                 {  
72.                     // Client socket closed  
73.                     printf("Client socket %d closed.\n", g_CliSocketArr[i]);  
74.                     closesocket(g_CliSocketArr[i]);  
75.                     if (i < g_iTotalConn-1)   
76.                     {  
77.                         g_CliSocketArr[i--] = g_CliSocketArr[--g_iTotalConn];  
78.                     }  
79.                 }   
80.                 else   
81.                 {  
82.                     // We reveived a message from client  
83.                     szMessage[ret] = '\0';  
84.                     send(g_CliSocketArr[i], szMessage, strlen(szMessage), 0);  
85.                 }  
86.             }  
87.         }  
88.     }  
89. }  

// write by larry// 2009-8-20// This is server using select model.#include "stdafx.h"#include <winsock.h>#include <stdio.h>#define PORT  5150#define MSGSIZE  1024#pragma comment(lib, "ws2_32.lib")int g_iTotalConn = 0;SOCKET g_CliSocketArr[FD_SETSIZE];DWORD WINAPI WorkerThread(LPVOID lpParam);int main(int argc, char* argv[]){WSADATA wsaData;SOCKET sListen, sClient;SOCKADDR_IN local, client;int iAddrSize = sizeof(SOCKADDR_IN);DWORD dwThreadId;// Initialize windows socket libraryWSAStartup(0x0202, &wsaData);// Create listening socketsListen = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);// Bindlocal.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));// Listenlisten(sListen, 3);// Create worker threadCreateThread(NULL, 0, WorkerThread, NULL, 0, &dwThreadId);while (TRUE) {// Accept a connectionsClient = accept(sListen, (sockaddr*)&client, &iAddrSize);printf("Accepted client:%s:%d\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));// Add socket to g_CliSocketArrg_CliSocketArr[g_iTotalConn++] = sClient;}return 0;}DWORD WINAPI WorkerThread(LPVOID lpParam){int i;fd_set fdread;int ret;struct timeval tv = {1, 0};char szMessage[MSGSIZE];while (TRUE) {FD_ZERO(&fdread);for (i = 0; i < g_iTotalConn; i++) {FD_SET(g_CliSocketArr[i], &fdread);}// We only care read eventret = select(0, &fdread, NULL, NULL, &tv);if (ret == 0) {// Time expiredcontinue;}for (i = 0; i < g_iTotalConn; i++) {if (FD_ISSET(g_CliSocketArr[i], &fdread)) {// A read event happened on g_CliSocketArrret = recv(g_CliSocketArr[i], szMessage, MSGSIZE, 0);if (ret == 0 || (ret == SOCKET_ERROR && WSAGetLastError() == WSAECONNRESET)) {// Client socket closedprintf("Client socket %d closed.\n", g_CliSocketArr[i]);closesocket(g_CliSocketArr[i]);if (i < g_iTotalConn-1) {g_CliSocketArr[i--] = g_CliSocketArr[--g_iTotalConn];}} else {// We reveived a message from clientszMessage[ret] = '\0';send(g_CliSocketArr[i], szMessage, strlen(szMessage), 0);}}}}}

这是异步模型中最简单的一种，服务器端的几个主要流程如下：

1.创建监听套接字，绑定，监听；
2.创建工作者线程；
3.创建一个套接字数组，用来存放当前所有活动的客户端套接字，每accept一个连接就更新一次数组；
4.接受客户端的连接。