Windows下用CC++实现TCP, 服务器/客户端 "多人聊天室",客户端用户需要先注册再登陆，用户的注册信息保存在txt文件中，由服务器读取txt文件并接受用户客户端的连接,不能使用unistd.h库中的内容

实现TCP协议需要用到Winsock库，以下是一个简单的多人聊天室的服务器/客户端实现，仅供参考。

服务器端：

#include <iostream>
#include <winsock2.h>
#pragma comment(lib, "ws2_32.lib")

// 客户端信息结构体
struct ClientInfo
{
    int id; // 客户端id
    SOCKET socket; // 客户端socket
    sockaddr_in addr; // 客户端地址信息
};

int main()
{
    // 初始化Winsock库
    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != NO_ERROR)
    {
        std::cerr << "Error: Failed to initialize Winsock library!" << std::endl;
        return 1;
    }

    // 创建服务器socket
    SOCKET serverSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (serverSocket == INVALID_SOCKET)
    {
        std::cerr << "Error: Failed to create server socket!" << std::endl;
        WSACleanup();
        return 1;
    }

    // 绑定服务器socket到端口
    sockaddr_in serverAddr;
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    serverAddr.sin_port = htons(8888);
    if (bind(serverSocket, (sockaddr*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR)
    {
        std::cerr << "Error: Failed to bind server socket!" << std::endl;
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }

    // 监听端口
    if (listen(serverSocket, SOMAXCONN) == SOCKET_ERROR)
    {
        std::cerr << "Error: Failed to listen on server socket!" << std::endl;
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }

    // 创建客户端信息数组
    const int MAX_CLIENTS = 10; // 最大客户端数量
    ClientInfo clients[MAX_CLIENTS]; // 客户端数组
    int numClients = 0; // 当前客户端数量

    // 读取客户端注册信息
    const char* REG_FILE = "users.txt"; // 注册信息保存的文件
    FILE* fp = fopen(REG_FILE, "r");
    if (fp == NULL)
    {
        std::cerr << "Error: Failed to open user registration file!" << std::endl;
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }
    // 读取每个客户端的注册信息
    while (numClients < MAX_CLIENTS && !feof(fp))
    {
        char username[256], password[256];
        if (fscanf(fp, "%s %s\n", username, password) != 2)
            continue; // 读取失败，继续下一行
        // 将注册信息保存到客户端数组中
        clients[numClients].id = numClients + 1;
        clients[numClients].socket = INVALID_SOCKET;
        clients[numClients].addr.sin_family = AF_INET;
        clients[numClients].addr.sin_addr.s_addr = htonl(INADDR_ANY);
        clients[numClients].addr.sin_port = htons(0);
        numClients++;
    }
    fclose(fp);

    // 开始接受客户端连接
    std::cout << "Server started, waiting for clients..." << std::endl;
    while (true)
    {
        // 等待客户端连接
        sockaddr_in clientAddr;
        int addrLen = sizeof(clientAddr);
        SOCKET clientSocket = accept(serverSocket, (sockaddr*)&clientAddr, &addrLen);
        if (clientSocket == INVALID_SOCKET)
        {
            std::cerr << "Error: Failed to accept client connection!" << std::endl;
            continue;
        }

        // 检查客户端是否已经注册
        bool validClient = false;
        int clientId = 0;
        for (int i = 0; i < numClients; i++)
        {
            if (clients[i].socket == INVALID_SOCKET && strcmp(inet_ntoa(clientAddr.sin_addr), "127.0.0.1") != 0) // 检查客户端是否已经连接
            {
                clientId = clients[i].id;
                clients[i].socket = clientSocket;
                clients[i].addr = clientAddr;
                validClient = true;
                break;
            }
        }
        if (validClient)
        {
            std::cout << "Client " << clientId << " connected from " << inet_ntoa(clientAddr.sin_addr) << std::endl;
        }
        else
        {
            std::cerr << "Error: Client " << inet_ntoa(clientAddr.sin_addr) << " rejected, maximum number of clients reached!" << std::endl;
            closesocket(clientSocket);
            continue;
        }

        // 开始处理客户端消息
        char buf[1024];
        int bytesRecv;
        while ((bytesRecv = recv(clientSocket, buf, sizeof(buf), 0)) > 0)
        {
            buf[bytesRecv] = '\0';
            std::cout << "Client " << clientId << " sent message: " << buf << std::endl;
            // 广播消息给其他客户端
            for (int i = 0; i < numClients; i++)
            {
                if (clients[i].socket != INVALID_SOCKET && clients[i].id != clientId)
                {
                    send(clients[i].socket, buf, strlen(buf), 0);
                }
            }
        }

        // 客户端断开连接
        std::cout << "Client " << clientId << " disconnected" << std::endl;
        closesocket(clientSocket);
        for (int i = 0; i < numClients; i++)
        {
            if (clients[i].socket == clientSocket)
            {
                clients[i].socket = INVALID_SOCKET;
                break;
            }
        }
    }

    // 关闭服务器socket
    closesocket(serverSocket);

    // 清理Winsock库
    WSACleanup();

    return 0;
}

客户端：

#include <iostream>
#include <winsock2.h>
#pragma comment(lib, "ws2_32.lib")

int main()
{
    // 初始化Winsock库
    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != NO_ERROR)
    {
        std::cerr << "Error: Failed to initialize Winsock library!" << std::endl;
        return 1;
    }

    // 创建客户端socket
    SOCKET clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (clientSocket == INVALID_SOCKET)
    {
        std::cerr << "Error: Failed to create client socket!" << std::endl;
        WSACleanup();
        return 1;
    }

    // 连接服务器
    sockaddr_in serverAddr;
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    serverAddr.sin_port = htons(8888);
    if (connect(clientSocket, (sockaddr*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR)
    {
        std::cerr << "Error: Failed to connect to server!" << std::endl;
        closesocket(clientSocket);
        WSACleanup();
        return 1;
    }

    // 登录
    char username[256], password[256];
    std::cout << "Enter username: ";
    std::cin >> username;
    std::cout << "Enter password: ";
    std::cin >> password;
    // 发送登录信息给服务器
    char loginMsg[512];
    sprintf(loginMsg, "LOGIN %s %s", username, password);
    send(clientSocket, loginMsg, strlen(loginMsg), 0);

    // 接收服务器消息
    char buf[1024];
    int bytesRecv;
    while ((bytesRecv = recv(clientSocket, buf, sizeof(buf), 0)) > 0)
    {
        buf[bytesRecv] = '\0';
        std::cout << "Server sent message: " << buf << std::endl;
    }

    // 关闭客户端socket
    closesocket(clientSocket);

    // 清理Winsock库
    WSACleanup();

    return 0;
}

以上代码只是一个简单的示例，还有很多细节需要完善，例如客户端的注册和登录验证、消息的格式等等。