基于Select模型的Windows TCP服务端和客户端程序示例

最近跟着刘远东老师的《C++百万并发网络通信引擎架构与实现（服务端、客户端、跨平台）》，Bilibili视频地址为C++百万并发网络通信引擎架构与实现（服务端、客户端、跨平台），重新复习下Windows以及Linux、MacOS下的C++网络编程。另外因为最近自己使用boost写了一个TCP服务器压力测试工具，模拟多个客户端设备连接指定的服务器，并定时向服务器推送数据，以测试服务器的并发连接数等，感觉看这个视频收货还蛮大的。
下面是Windows下使用Select模型实现的一个简易TCP服务端和客户端，客户端添加了一个命令输入线程，代码如下：
一、服务端程序代码如下：
// Server.cpp

#include <stdio.h>
#include <iostream>
#include <vector>
#include <algorithm>

#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <WinSock2.h>

#pragma comment(lib, "ws2_32.lib")

using namespace std;

// 要考虑字节对齐问题（32位和64位，平台和系统）
enum CMDTYPE
{
 CMD_LOGIN,			// 登录
 CMD_LOGIN_RESULT,	// 登录返回结果
 CMD_LOGOUT,			// 登出
 CMD_LOGOUT_RESULT,	// 登出返回结果
 CMD_NEW_USER_JOIN,	// 新用户加入
 CMD_ERROR			// 错误
};

// 消息头
struct DataHeader
{
 int	cmd;			// 命令类型
 int dataLength;		// 消息体的数据长度
};

// 消息体
// DataPackage
// 登录
struct Login : public DataHeader 
{
 Login()
 {
 	dataLength = sizeof(Login);
 	cmd = CMD_LOGIN;
 }
 char userName[32];
 char passWord[32];
};

// 登录结果
struct LoginResult : public DataHeader
{
 LoginResult()
 {
 	dataLength = sizeof(Login);
 	cmd = CMD_LOGIN_RESULT;
 	result = 0;
 }
 int result;
};

// 登出
struct Logout : public DataHeader
{
 Logout()
 {
 	dataLength = sizeof(Logout);
 	cmd = CMD_LOGOUT;
 }
 char userName[32];
};

// 登出结果
struct LogoutResult : public DataHeader
{
 LogoutResult()
 {
 	dataLength = sizeof(LogoutResult);
 	cmd = CMD_LOGOUT_RESULT;
 	result = 0;
 }
 int result;
};

// 新用户加入
// 登出
struct NewUserJoin : public DataHeader
{
 NewUserJoin()
 {
 	dataLength = sizeof(NewUserJoin);
 	cmd = CMD_NEW_USER_JOIN;
 	sock = 0;
 }
 int sock;
};

std::vector<SOCKET> g_clientList;	// 客户端套接字列表

int processor(SOCKET sock)
{
 // 缓冲区(4096字节)
 char szRecv[4096] = {};
 // 5、接收客户端的请求
 // 先接收消息头
 int recvLen = recv(sock, szRecv, sizeof(DataHeader), 0);
 DataHeader *pHeader = (DataHeader*)szRecv;
 if (recvLen <= 0)
 {
 	printf("客户端<Socket=%d>已退出，任务结束...", sock);
 	return -1;
 }

 // 6、处理请求
 switch (pHeader->cmd)
 {
 case CMD_LOGIN:
 {
 	Login *login = (Login*)szRecv;

 	recv(sock, szRecv + sizeof(DataHeader), pHeader->dataLength - sizeof(DataHeader), 0);
 	printf("收到客户端<Socket=%d>请求：CMD_LOGIN, 数据长度：%d, userName：%s Password： %s
",
 		sock, login->dataLength, login->userName, login->passWord);
 	// 忽略判断用户名和密码是否正确的过程
 	LoginResult ret;
 	send(sock, (char*)&ret, sizeof(LoginResult), 0);
 }
 break;
 case CMD_LOGOUT:
 {
 	Logout *logout = (Logout*)szRecv;

 	recv(sock, szRecv + sizeof(DataHeader), pHeader->dataLength - sizeof(DataHeader), 0);
 	printf("收到客户端<Socket=%d>请求：CMD_LOGOUT, 数据长度：%d, userName：%s
",
 		sock, logout->dataLength, logout->userName);
 	LogoutResult ret;
 	send(sock, (char*)&ret, sizeof(LogoutResult), 0);
 }
 break;
 default:
 {
 	DataHeader header = { 0, CMD_ERROR };
 	send(sock, (char*)&header, sizeof(header), 0);
 	break;
 }
 }

 return 0;
}

int main(int argc, char *agrv[])
{
 // 加载套接字库
 WORD wVersionRequested;
 WSADATA wsaData;
 int err;

 wVersionRequested = MAKEWORD(2, 2);
 // 启动Windows Socket 2.x环境
 err = WSAStartup(wVersionRequested, &wsaData);

 // 使用Socket API建立简易的TCP服务端
 if (err != 0) {
 	/* Tell the user that we could not find a usable */
 	/* WinSock DLL.                                  */
 	return 1;
 }

 /* Confirm that the WinSock DLL supports 2.2.*/
 /* Note that if the DLL supports versions greater    */
 /* than 2.2 in addition to 2.2, it will still return */
 /* 2.2 in wVersion since that is the version we      */
 /* requested.                                        */

 if (LOBYTE(wsaData.wVersion) != 2 ||
 	HIBYTE(wsaData.wVersion) != 2) {
 	/* Tell the user that we could not find a usable */
 	/* WinSock DLL.                                  */
 	WSACleanup();
 	return 1;
 }

 /* The WinSock DLL is acceptable. Proceed. */
  //----------------------
// Create a SOCKET for listening for
// incoming connection requests.
 SOCKET ListenSocket;
 ListenSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
 if (ListenSocket == INVALID_SOCKET) {
 	printf("Error at socket(): %ld
", WSAGetLastError());
 	WSACleanup();
 	return 1;
 }

 //----------------------
 // The sockaddr_in structure specifies the address family,
 // IP address, and port for the socket that is being bound.
 sockaddr_in service;
 service.sin_family = AF_INET;
 //service.sin_addr.s_addr = inet_addr("127.0.0.1");
 service.sin_addr.s_addr = INADDR_ANY;
 service.sin_port = htons(27015);

 if (bind(ListenSocket,
 	(SOCKADDR*)&service,
 	sizeof(service)) == SOCKET_ERROR) {
 	printf("bind() failed.绑定网络端口失败
");
 	closesocket(ListenSocket);
 	WSACleanup();
 	return 1;
 }
 else
 {
 	printf("绑定网络端口成功...
");
 }

 //----------------------
 // Listen for incoming connection requests.
 // on the created socket
 if (listen(ListenSocket, 5) == SOCKET_ERROR) {
 	printf("错误，监听网络端口失败...
");
 	closesocket(ListenSocket);
 	WSACleanup();
 	return 1;
 }
 else
 {
 	printf("监听网络端口成功...
");
 }

 printf("等待客户端连接...
");

 while (true)
 {
 	// Berkeley sockets
 	fd_set readfds;			// 描述符(socket)集合
 	fd_set writefds;
 	fd_set exceptfds;

 	// 清理集合
 	FD_ZERO(&readfds);
 	FD_ZERO(&writefds);
 	FD_ZERO(&exceptfds);

 	// 将描述符(socket)加入集合
 	FD_SET(ListenSocket, &readfds);
 	FD_SET(ListenSocket, &writefds);
 	FD_SET(ListenSocket, &exceptfds);

 	for (int n = (int)g_clientList.size() - 1;  n >= 0 ; n--)
 	{
 		FD_SET(g_clientList[n], &readfds);
 	}

 	// 设置超时时间 select 非阻塞
 	timeval timeout = { 1, 0 };
 	
 	// nfds是一个整数值，是指fd_set集合中所有描述符(socket)的范围，而不是数量
 	// 即是所有文件描述符最大值+1 在Windows中这个参数可以写0
 	//int ret = select(ListenSocket + 1, &readfds, &writefds, &exceptfds, NULL);
 	int ret = select(ListenSocket + 1, &readfds, &writefds, &exceptfds, &timeout);
 	if (ret < 0)
 	{
 		printf("select任务结束,called failed:%d!
", WSAGetLastError());
 		break;
 	}

 	// 是否有数据可读
 	// 判断描述符(socket)是否在集合中
 	if (FD_ISSET(ListenSocket, &readfds))
 	{
 		//FD_CLR(ListenSocket, &readfds);

 		// Create a SOCKET for accepting incoming requests.
 		// 4. accept 等待接受客户端连接
 		SOCKADDR_IN clientAddr = {};
 		int nAddrLen = sizeof(SOCKADDR_IN);
 		SOCKET ClientSocket = INVALID_SOCKET;
 		ClientSocket = accept(ListenSocket, (SOCKADDR*)&clientAddr, &nAddrLen);
 		if (INVALID_SOCKET == ClientSocket) {
 			printf("accept() failed: %d,接收到无效客户端Socket
", WSAGetLastError());
 			return 1;
 		}
 		else
 		{
 			// 有新的客户端加入，向之前的所有客户端群发消息
 			for (int n = (int)g_clientList.size() - 1; n >= 0; n--)
 			{
 				NewUserJoin userJoin;
 				send(g_clientList[n], (const char*)&userJoin, sizeof(NewUserJoin), 0);
 			}

 			g_clientList.push_back(ClientSocket);
 			// 客户端连接成功，则显示客户端连接的IP地址和端口号
 			printf("新客户端<Sokcet=%d>加入,Ip地址：%s,端口号：%d
", ClientSocket, inet_ntoa(clientAddr.sin_addr),
 				ntohs(clientAddr.sin_port));
 		}
 	}

 	for (int i = 0; i < (int)readfds.fd_count - 1; ++i)
 	{
 		if (-1 == processor(readfds.fd_array[i]))
 		{
 			auto iter = std::find(g_clientList.begin(), g_clientList.end(), 
 									readfds.fd_array[i]);
 			if (iter != g_clientList.end())
 			{
 				g_clientList.erase(iter);
 			}
 		}
 	}

 	//printf("空闲时间处理其他业务...
");
 }
 
 for (int n = (int)g_clientList.size() - 1; n >= 0; n--)
 {
 	closesocket(g_clientList[n]);
 }

 // 8.关闭套接字
 closesocket(ListenSocket);
 // 9.清除Windows Socket环境
 WSACleanup();

 printf("服务端已退出，任务结束
");

 getchar();

 return 0;
}

二、客户端程序代码如下：
// Client.cpp

#include <stdio.h>

#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <WinSock2.h>

#include <thread>

#pragma comment(lib, "ws2_32.lib")

// 要考虑字节对齐问题（32位和64位，平台和系统）
enum CMDTYPE
{
	CMD_LOGIN,			// 登录
	CMD_LOGIN_RESULT,	// 登录返回结果
	CMD_LOGOUT,			// 登出
	CMD_LOGOUT_RESULT,	// 登出返回结果
	CMD_NEW_USER_JOIN,	// 新用户加入
	CMD_ERROR			// 错误
};

// 消息头
struct DataHeader
{
	int	cmd;			// 命令类型
	int dataLength;		// 消息体的数据长度
};

// 消息体
// DataPackage
// 登录
struct Login : public DataHeader
{
	Login()
	{
		dataLength = sizeof(Login);
		cmd = CMD_LOGIN;
	}
	char userName[32];
	char passWord[32];
};

// 登录结果
struct LoginResult : public DataHeader
{
	LoginResult()
	{
		dataLength = sizeof(Login);
		cmd = CMD_LOGIN_RESULT;
		result = 0;
	}
	int result;
};

// 登出
struct Logout : public DataHeader
{
	Logout()
	{
		dataLength = sizeof(Logout);
		cmd = CMD_LOGOUT;
	}
	char userName[32];
};

// 登出结果
struct LogoutResult : public DataHeader
{
	LogoutResult()
	{
		dataLength = sizeof(LogoutResult);
		cmd = CMD_LOGOUT_RESULT;
		result = 0;
	}
	int result;
};

// 新用户加入
// 登出
struct NewUserJoin : public DataHeader
{
	NewUserJoin()
	{
		dataLength = sizeof(NewUserJoin);
		cmd = CMD_NEW_USER_JOIN;
		sock = 0;
	}
	int sock;
};


int processor(SOCKET sock)
{
	// 缓冲区(4096字节)
	char szRecv[4096] = {};
	// 5、接收客户端的请求
	// 先接收消息头
	int recvLen = recv(sock, szRecv, sizeof(DataHeader), 0);
	DataHeader *pHeader = (DataHeader*)szRecv;
	if (recvLen <= 0)
	{
		printf("与服务器断开连接，任务结束...");
		return -1;
	}

	// 6、处理请求
	switch (pHeader->cmd)
	{
	case CMD_LOGIN_RESULT:
	{
		recv(sock, szRecv + sizeof(DataHeader), pHeader->dataLength - sizeof(DataHeader), 0);

		LoginResult *loginRes = (LoginResult*)szRecv;

		printf("收到服务器消息：CMD_LOGIN_RESULT, 数据长度：%d, result：%d
",
			loginRes->dataLength, loginRes->result);
	}
	break;
	case CMD_LOGOUT_RESULT:
	{
		recv(sock, szRecv + sizeof(DataHeader), pHeader->dataLength - sizeof(DataHeader), 0);

		LogoutResult *logoutRes = (LogoutResult*)szRecv;

		printf("收到服务器消息：CMD_LOGOUT_RESULT, 数据长度：%d, result：%d
",
			logoutRes->dataLength, logoutRes->result);
	}
	case CMD_NEW_USER_JOIN:
	{
		recv(sock, szRecv + sizeof(DataHeader), pHeader->dataLength - sizeof(DataHeader), 0);

		NewUserJoin *userJoin = (NewUserJoin*)szRecv;

		printf("收到服务器消息：CMD_NEW_USER_JOIN, 数据长度：%d
",
			userJoin->dataLength);
	}
	break;
	}

	return 0;
}

bool g_bRun = true;		// 是否退出程序

// 命令输入 线程入口函数
void cmdThread(SOCKET sock)
{
	while (true)
	{
		// 输入请求命令
		char cmdBuf[128] = { 0 };
		printf("请输入命令：[exit | login | logout | other]
");
		scanf("%s", &cmdBuf);

		// 处理请求
		if (0 == strcmp(cmdBuf, "exit"))
		{
			g_bRun = false;
			printf("退出cmdThread线程...
");
			break;
		}
		else if (0 == strcmp(cmdBuf, "login"))
		{
			// 5.向服务器发送命令请求
			Login login;
			strcpy(login.userName, "ccf");
			strcpy(login.passWord, "ccfPwd");

			send(sock, (const char*)&login, sizeof(login), 0);
		}
		else if (0 == strcmp(cmdBuf, "logout"))
		{
			// 5.向服务器发送命令请求
			Logout logout;
			strcpy(logout.userName, "ccf");
			send(sock, (const char*)&logout, sizeof(logout), 0);
		}
		else
		{
			printf("不支持的命令，请重新输入.
");
		}
	}
}

int main(int argc, char *argv[])
{
	//----------------------
	// Initialize Winsock
	WSADATA wsaData;
	int iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
	if (iResult != NO_ERROR)
	{
		printf("WSAStartup() 错误，创建套接字库失败!
");
		return -1;
	}

	//----------------------
	// Create a SOCKET for connecting to server
	SOCKET ConnectSocket;
	ConnectSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (ConnectSocket == INVALID_SOCKET) {
		printf("创建套接字失败: %ld
", WSAGetLastError());
		WSACleanup();
		return -1;
	}

	//----------------------
	// The sockaddr_in structure specifies the address family,
	// IP address, and port of the server to be connected to.
	sockaddr_in clientService;
	clientService.sin_family = AF_INET;
	clientService.sin_addr.s_addr = inet_addr("127.0.0.1");
	clientService.sin_port = htons(27015);

	//----------------------
	// Connect to server.
	if (connect(ConnectSocket, (SOCKADDR*)&clientService, sizeof(clientService)) == SOCKET_ERROR) {
		printf("连接服务器失败.
");
		WSACleanup();
		return -1;
	}

	printf("客户端成功连接到服务器.
");

	// 循环输入命令
	// 启动线程
	std::thread thread_(cmdThread, ConnectSocket);		
	thread_.detach();

	while (g_bRun)
	{
		fd_set fdReads;
		FD_ZERO(&fdReads);

		FD_SET(ConnectSocket, &fdReads);

		timeval timeout = { 0, 0 };
		int ret = select(ConnectSocket, &fdReads, NULL, NULL, &timeout);
		if (ret < 0)
		{
			printf("select任务结束1...
");
			break;
		}

		if (FD_ISSET(ConnectSocket, &fdReads))
		{
			//FD_CLR(ConnectSocket, &fdReads);

			// 有数据可读，可以处理了
			if (-1 == processor(ConnectSocket))
			{
				printf("select任务结束2
");
				break;
			}
		}

		/*Login login;
		strcpy(login.userName, "ccf");
		strcpy(login.passWord, "ccfPwd");

		send(ConnectSocket, (const char*)&login, sizeof(Login), 0);*/
		//Sleep(1000);	// 发送登录数据后延时1s

		//printf("空闲时间处理其他业务...
");
	}
	
	WSACleanup();

	printf("客户端已退出...
");

	getchar();

	return 0;
}

之前在CSDN上看到一篇博客，是基于UDP的Linux C++简单聊天室实现，我把源代码重新整理并放在个人的GitHub上面基于UDP的Linux C++简单聊天室，同样是使用select模型实现的，有兴趣可以看一下。