TCP之 select模型

前记：select模型主要用于解决tcp通信中，每次处理一个独立的客户都要单独的开线程，这样会导致客户连接数很大时，线程数也会很多。而使用select就会将线程缩减至2个，一个主线程用于接收Accept客户端的连接，另外一个子线程用于监听已经连接上来的客户端是否有信号状态，如果有信号则进行相应的消息处理。

服务端：

#include "stdafx.h"
#include <stdio.h>
#include <WinSock2.h>//必须放在windows.h前面
#include <Windows.h>
#include <stdlib.h>
#pragma comment(lib, "ws2_32.lib")

fd_set g_fdClientSock;
int clientNum = 0;

DWORD WINAPI ListenThreadProc(LPARAM lparam)
{

	fd_set fdRead;
	FD_ZERO(&fdRead);
	int nRet = 0;
	char *recvBuffer = (char*)malloc(1024);
	if (!recvBuffer)
	{
		return -1;
	}
	memset(recvBuffer, 0, 1024);
	while (TRUE)
	{
		fdRead = g_fdClientSock;
		timeval vt;

		vt.tv_sec = 0;
		vt.tv_usec = 0;
		nRet = select(0, &fdRead, 0,0,&vt);//会阻塞检查集合中所有socket是否有信号
		if (nRet != SOCKET_ERROR)
		{
			for (int i=0; i<g_fdClientSock.fd_count; i++)
			{
				if (FD_ISSET(g_fdClientSock.fd_array[i], &fdRead))
				{
					memset(recvBuffer, 0, 1024);
					nRet = recv(g_fdClientSock.fd_array[i], recvBuffer, 1024, 0);
					if (nRet >0)
					{
						//todo:
						printf("接收到数据：%s", recvBuffer);
						send(g_fdClientSock.fd_array[i], recvBuffer, strlen(recvBuffer), 0);
					}
					else//如果接收失败，则从集合中清除响应socket，并把客户端数量减1
					{
						closesocket(g_fdClientSock.fd_array[i]);
						clientNum--;
						FD_CLR(g_fdClientSock.fd_array[i], &g_fdClientSock);
					}
				}
			}
		}
	}

	if (recvBuffer)
	{
		free(recvBuffer);
		recvBuffer=nullptr;
	}
	return 0;
}

void main()
{
	int port = 5099;
	WSADATA wsaData;
	if(WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
	{
		printf("Failed to load Winsock");
		return;
	}

	//创建用于监听的套接字  AF_INET：IPV4版本
	SOCKET sockSrv = socket(AF_INET, SOCK_STREAM, 0);
	if (sockSrv == INVALID_SOCKET)
	{
		return;
	}

	//地址绑定-告诉操作系统是在哪一个地址及端口
	SOCKADDR_IN addrSrv;
	addrSrv.sin_family = AF_INET;
	addrSrv.sin_port = htons(port); //1024以上的端口号，htons本地转换为网络数据
	addrSrv.sin_addr.S_un.S_addr = htonl(INADDR_ANY);//电脑上所有的网络ip

	int retVal = bind(sockSrv, (LPSOCKADDR)&addrSrv, sizeof(SOCKADDR_IN));
	if(retVal == SOCKET_ERROR)
	{
		printf("绑定bind失败:%d\n", WSAGetLastError());
		return;
	}

	if(listen(sockSrv,5/*SOMAXCONN*/) ==SOCKET_ERROR)
	{
		printf("监听listen失败:%d", WSAGetLastError());
		return;
	}

	SOCKADDR_IN addrClient;//用于获取连接上来的人的地址信息
	int len = sizeof(SOCKADDR);

	CreateThread(NULL,NULL, (LPTHREAD_START_ROUTINE)ListenThreadProc, NULL, NULL, NULL);

	while(clientNum < FD_SETSIZE)
	{
		//等待客户请求到来	
		SOCKET clientSock = accept(sockSrv, (SOCKADDR *) &addrClient, &len);
		if(clientSock == SOCKET_ERROR)
		{
			printf("接收Accept失败:%d", WSAGetLastError());
			break;
		}
		else
		{
			printf("接收Accept到客户端IP:[%s]\n", inet_ntoa(addrClient.sin_addr));
		}
		FD_SET(clientSock, &g_fdClientSock);//添加到集合中去
		clientNum++;//每次接收到一个人就+1，目前最多接收64个客户
	}

	closesocket(sockSrv);
	WSACleanup();
	system("pause");
}

客户端：

// Tcp_client.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <WinSock2.h>
#include <stdio.h>
#pragma comment(lib, "ws2_32.lib")

void main()
{
	//加载套接字
	WSADATA wsaData;
	char buff[1024];
	memset(buff, 0, sizeof(buff));

	if(WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
	{
		printf("Failed to load Winsock");
		return;
	}

	SOCKADDR_IN addrSrv;
	addrSrv.sin_family = AF_INET;
	addrSrv.sin_port = htons(5099);//http默认端口
	addrSrv.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");

	//创建套接字
	SOCKET sockClient = socket(AF_INET, SOCK_STREAM, 0);
	if(SOCKET_ERROR == sockClient){
		printf("Socket() error:%d", WSAGetLastError());
		return;
	}

	//向服务器发出连接请求
	if(connect(sockClient, (struct  sockaddr*)&addrSrv, sizeof(addrSrv)) == INVALID_SOCKET){
		printf("Connect failed:%d", WSAGetLastError());
		return;
	}

	int iRecvLen = 0;

	//发送数据
	char* buffSend = "hello, this is a Client....";
	iRecvLen = send(sockClient, buffSend, strlen(buffSend), 0);
	
	
	//接收数据
	iRecvLen = recv(sockClient, buff, sizeof(buff), 0);
	printf("%s\n", buff);

	//关闭套接字
	closesocket(sockClient);
	WSACleanup();
	system("pause");
}