C++ SQLite3 网络服务器：设备状态监控及建议生成

本项目使用 C++ 开发了一个基于 SQLite3 数据库的网络服务器，用于监控设备状态并根据状态生成建议。服务器通过 Socket 接收客户端请求，查询数据库获取设备状态信息，并根据信息生成建议，最后将建议发送回客户端。

服务器代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <arpa/inet.h>
#include <sqlite3.h>
#include <netinet/in.h>

#define MAX_BUFFER_SIZE 1024

typedef struct {
    int uid;
    char device_name[20];
    char device_state[20];
    char value[20];
    char mode[20];
} Status;

typedef struct {
    int sockfd;
    struct sockaddr_in client_addr;
    socklen_t client_addr_len;
    sqlite3 *db;
} ServerContext;

void handleClientRequest(ServerContext *context) {
    char buffer[MAX_BUFFER_SIZE];
    int userid;

    // 接收客户端发送的userid
    ssize_t recvSize = recv(context->sockfd, &userid, sizeof(int), 0);

    if (recvSize == -1) {
        perror("userid接受失败\nrecv");
        return;
    } else if (recvSize == 0) {
        perror("客户端已关闭连接");
        return;
    } else if (recvSize != sizeof(int)) {
        perror("接收到的字节数不正确");
        return;
    }
    userid = ntohl(userid); // 将网络字节序转换为主机字节序
    printf("客户端已连接\n");
    printf("userid:%d\n", userid);
    // 查询数据库获取设备状态信息
    char sql[100];
    snprintf(sql, sizeof(sql), "SELECT * FROM Status WHERE uid = %d", userid);
    sqlite3_stmt *stmt = NULL;
    int rc = sqlite3_prepare_v2(context->db, sql, -1, &stmt, NULL);
    if (rc != SQLITE_OK) {
        fprintf(stderr, "无法执行的语句: %s\n", sqlite3_errmsg(context->db));
        return;
    }

    Status status;
    memset(&status, 0, sizeof(Status)); // 清空status结构体
    while (sqlite3_step(stmt) == SQLITE_ROW) {
        status.uid = sqlite3_column_int(stmt, 1);

        const unsigned char *device_name = sqlite3_column_text(stmt, 2);
        if (device_name != NULL) {
            strncpy(status.device_name, device_name, sizeof(status.device_name)-1);
            status.device_name[sizeof(status.device_name)-1] = '\0';
        }

        const unsigned char *device_state = sqlite3_column_text(stmt, 3);
        if (device_state != NULL) {
            strncpy(status.device_state, device_state, sizeof(status.device_state)-1);
            status.device_state[sizeof(status.device_state)-1] = '\0';
        }

        const unsigned char *value = sqlite3_column_text(stmt, 4);
        if (value != NULL) {
            strncpy(status.value, value, sizeof(status.value)-1);
            status.value[sizeof(status.value)-1] = '\0';
        }

        const unsigned char *mode = sqlite3_column_text(stmt, 5);
        if (mode != NULL) {
            strncpy(status.mode, mode, sizeof(status.mode)-1);
            status.mode[sizeof(status.mode)-1] = '\0';
        }
    }
    sqlite3_finalize(stmt); // 释放查询结果集

    if (strlen(status.device_name) == 0) {
        perror("接收设备状态信息失败");
        return;
    }

    // 分析设备状态并生成建议
    char suggestion[MAX_BUFFER_SIZE];
    if (strcmp(status.device_name, "空调") == 0) {
        int temperature = atoi(status.value);
        if (temperature < 24) {
            snprintf(suggestion, sizeof(suggestion), "空调温度过低，建议提高温度至26℃");
        } else {
            snprintf(suggestion, sizeof(suggestion), "空调温度正常");
        }
    } else if (strcmp(status.device_name, "加湿器") == 0) {
        int humidity = atoi(status.value);
        if (humidity < 40 || humidity > 70) {
            snprintf(suggestion, sizeof(suggestion), "加湿器湿度过高或过低，建议调整加湿器湿度");
        } else {
            snprintf(suggestion, sizeof(suggestion), "加湿器湿度正常");
        }
    } else {
        snprintf(suggestion, sizeof(suggestion), "设备状态未知");
    }

    // 向客户端发送建议
    ssize_t sendSize = send(context->sockfd, suggestion, strlen(suggestion), 0);
    if (sendSize == -1) {
        perror("发送失败\nsend");
        return;
    }
    else{
    printf("发送成功!");
    }
    printf("%s\n", suggestion);
}

int main() {
    printf("正在连接中...\n");
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd == -1) {
        perror("连接失败\nsocket");
        return 1;
    }

    struct sockaddr_in server_addr;
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_port = htons(12345);

    if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        perror("连接失败\nbind");
        close(sockfd);
        return 1;
    }

    if (listen(sockfd, 5) == -1) {
        perror("连接失败\nlisten");
        close(sockfd);
        return 1;
    }

    sqlite3 *db;
    int rc = sqlite3_open("/mnt/g/Qt/Client/Smarthome_Client/database/database.db", &db);
    if (rc != SQLITE_OK) {
        fprintf(stderr, "数据库打开失败: %s\n", sqlite3_errmsg(db));
        return 1;
    }

    ServerContext context;
    context.sockfd = sockfd;
    context.client_addr_len = sizeof(context.client_addr);
    context.db = db;

    fd_set readfds;
    int maxfd = sockfd;

    while (1) {
        FD_ZERO(&readfds);
        FD_SET(sockfd, &readfds);

        int activity = select(maxfd + 1, &readfds, NULL, NULL, NULL);
        if (activity == -1) {
            perror("select");
            break;
        }

        if (FD_ISSET(sockfd, &readfds)) {
            int clientSockfd = accept(sockfd, (struct sockaddr *)&context.client_addr, &context.client_addr_len);
            if (clientSockfd == -1) {
                perror("套接字接收失败\naccept");
                break;
            }

            context.sockfd = clientSockfd;
            handleClientRequest(&context);

            close(clientSockfd);
        }
    }
    sqlite3_close(db);
    close(sockfd);
    printf("服务器已关闭\n");

    return 0;
}

客户端代码：

#include "procession.h"
#include "ui_procession.h"
#include <QAbstractSocket>
#include <QDebug>

Procession::Procession(int userid,QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Procession),
    userid(userid)
{
    ui->setupUi(this);
    processionWidget();
    m_socket = new QTcpSocket(this);
    //connect(ui->connectBtn, &QPushButton::clicked, this, &Procession::on_connectBtn_clicked);
    connect(m_socket, &QTcpSocket::readyRead, this, &Procession::readyRead);
    connect(m_socket, &QTcpSocket::connected, this, &Procession::connected);
    connect(m_socket, &QTcpSocket::disconnected,this,&Procession::disconnected);
    connect(m_socket, QOverload<QAbstractSocket::SocketError>::of(&QTcpSocket::error), this, &Procession::displayError);
}

Procession::~Procession()
{
    delete ui;
    // 在程序结束前关闭套接字
    m_socket->close();
}

void Procession::processionWidget()
{
    setWindowTitle("服务器通信");
    setAutoFillBackground(true);
    QPalette palette=this->palette();
    QPixmap pixmap(":/user/image/image/net.jpg");
    palette.setBrush(QPalette::Window, QBrush(pixmap));
    setPalette(palette);
    setFixedSize(600,400);
}


void Procession::connected()
{
    ui->message->append("连接成功");
    QByteArray block;
    QDataStream out(&block, QIODevice::WriteOnly);
    out << static_cast<quint32>(this->userid);
    qDebug()<<static_cast<quint32>(this->userid);
    if (m_socket->write(block) == -1) {
        ui->message->append("发送userid失败");
        m_socket->close();
    }
    m_socket->close(); // 关闭套接字
}


void Procession::disconnected()
{
    ui->message->append("连接失败");
    m_socket->close();
}

void Procession::readyRead()
{
    QByteArray data = m_socket->readAll();
    if (data.isEmpty()) {
        ui->message->append("读取的数据为空");
        return;
    }
    // 解析服务器返回的数据
    QDataStream in(&data, QIODevice::ReadOnly);
    QString suggestion;
    in >> suggestion; // 使用重载的 >> 运算符来读取数据
    if (in.status() != QDataStream::Ok) {
        ui->message->append("解析服务器返回的数据失败");
        return;
    }
    ui->message->append(suggestion);
    m_socket->close();
}

void Procession::displayError(QAbstractSocket::SocketError error)
{
    QString errorMessage;
    switch (error) {
    case QAbstractSocket::ConnectionRefusedError:
        errorMessage = "连接被拒绝";
        break;
    case QAbstractSocket::RemoteHostClosedError:
        errorMessage = "远程主机关闭";
        break;
    case QAbstractSocket::HostNotFoundError:
        errorMessage = "未找到主机";
        break;
    case QAbstractSocket::SocketTimeoutError:
        errorMessage = "连接超时";
        break;
    case QAbstractSocket::NetworkError:
        errorMessage = "网络错误";
        break;
    default:
        errorMessage = "未知错误";
        break;
    }
    ui->message->append("连接失败：" + errorMessage);
}

void Procession::on_connectBtn_clicked()
{
    if (m_socket->state() == QAbstractSocket::ConnectedState) {
        m_socket->disconnectFromHost(); // 先关闭套接字
    }

    ui->message->append("已经连接上服务器");
    QString ip = ui->IP->text();
    QString port = ui->port->text();

    if (ip.isEmpty() || port.isEmpty()) {
        ui->message->clear();
        ui->message->append("请输入有效的IP地址和端口号");
        return;
    }

    ui->message->clear();
    ui->message->append("正在连接中...");
    m_socket->connectToHost(ip, static_cast<quint16>(ui->port->text().toInt()));
}

#include <QWidget>
#include <QTcpSocket>
#include <QDebug>
#include <QByteArray>
#include <QTcpSocket>

namespace Ui {
class Procession;
}

class Procession : public QWidget
{
    Q_OBJECT

public:
    explicit Procession(int userid,QWidget *parent = nullptr);
    ~Procession();
    void processionWidget();

private slots:
    //void on_pushButton_clicked();
    void connected();
    void disconnected();
    void readyRead();
    void displayError(QAbstractSocket::SocketError error);

    void on_connectBtn_clicked();

private:
    Ui::Procession *ui;
    int userid;
    QTcpSocket* m_socket;
};

#endif // PROCESSION_H


客户端IP=127.0.0.1 Port=12345




root@WIN-K3C9KG85CB8:/home/SmartHome/Server# valgrind --leak-check=full ./main.exec
==3155== Memcheck, a memory error detector
==3155== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==3155== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==3155== Command: ./main.exec
==3155==
正在连接中...
建议发送成功！客户端已连接
userid:123
空调温度正常



客户端运行结果
正在连接中...
连接成功
解析服务器返回的数据失败
连接失败：远程主机关闭
连接失败

ifconfig运行结果
root@WIN-K3C9KG85CB8:/home/SmartHome/Server# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.21.91.176  netmask 255.255.240.0  broadcast 172.21.95.255
        inet6 fe80::215:5dff:fedd:6558  prefixlen 64  scopeid 0x20<link>
        ether 00:15:5d:dd:65:58  txqueuelen 1000  (Ethernet)
        RX packets 11543  bytes 15485605 (15.4 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2910  bytes 319768 (319.7 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 511  bytes 31391 (31.3 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 511  bytes 31391 (31.3 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

如何解决

客户端地址已设置成172.21.91.176

服务器运行结果
root@WIN-K3C9KG85CB8:/home/SmartHome/Server# valgrind --leak-check=full ./main.exec
==3194== Memcheck, a memory error detector
==3194== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==3194== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==3194== Command: ./main.exec
==3194==
正在连接中...
建议发送成功！客户端已连接
userid:123
空调温度正常

第二次点击客户端按键时服务器运行结果
客户端已连接
userid:123
空调温度正常
第三次点击客户端按键服务器运行结果
客户端已连接
userid:123
空调温度正常

客户端运行结果一直是下面这样
正在连接中...
连接成功
解析服务器返回的数据失败
连接失败：远程主机关闭
连接失败

客户端解析服务器发来的消息的代码
void Procession::readyRead()
{
    QByteArray data = m_socket->readAll();
    if (data.isEmpty()) {
        ui->message->append("读取的数据为空");
        return;
    }
    // 解析服务器返回的数据
    QDataStream in(&data, QIODevice::ReadOnly);
    QString suggestion;
    in >> suggestion; // 使用重载的 >> 运算符来读取数据
    if (in.status() != QDataStream::Ok) {
        ui->message->append("解析服务器返回的数据失败");
        return;
    }
    ui->message->append(suggestion);
    m_socket->close();
}

客户端运行结果
正在连接中...
连接成功
连接失败

有什么问题，该如何解决内容：根据服务器运行结果和客户端运行结果，可以看出客户端成功连接服务器后，服务器发送的建议消息无法正确解析。

问题可能出在以下几个方面：

1. 数据格式不一致：服务器发送的建议消息是字符串类型，客户端接收时可能没有正确解析为QString类型。可以在客户端的readyRead()函数中添加一些调试输出，查看接收到的原始数据是否正确。

2. 数据读取问题：在客户端的readyRead()函数中，使用了QDataStream的读取操作符（>>）来读取服务器发送的数据。这种方式需要保证数据的格式和顺序与发送时一致。可以尝试使用其他方式来读取数据，如使用QByteArray的fromRawData()函数来创建QString对象。

3. 数据接收不完整：在客户端的readyRead()函数中，使用了m_socket->readAll()来读取接收到的数据。这种方式可能导致数据接收不完整，需要保证接收到的数据是完整的建议消息。

建议逐步调试，查看每个步骤中的数据是否正确，以及是否按照预期进行解析。可以使用调试工具或添加一些调试输出来辅助调试。