Qt网络通信：与C++服务器进行JSON数据交互

概述

本文将介绍如何使用Qt框架构建一个简单的客户端程序，该程序通过网络与C++服务器进行通信，并使用JSON格式进行数据交互。客户端程序将用户ID发送到服务器，服务器根据用户ID查询数据库获取用户的最新温度和湿度值，并根据这些值生成建议，最终将建议作为响应发送回客户端。

客户端代码 (procession.h)cpp#ifndef PROCESSION_H#define PROCESSION_H

#include #include #include

namespace Ui {class Procession;}

class Procession : public QWidget{ Q_OBJECT

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

private slots: void connectToServer(); //和服务器通信 void handleServerResponse(QNetworkReply *reply); //和服务器连接回应

private: Ui::Procession *ui; int userid; QNetworkAccessManager *networkManager;};

#endif // PROCESSION_H

客户端代码 (procession.cpp)cpp#include 'procession.h'#include 'ui_procession.h'#include #include #include

//通过发送POST请求将用户ID发送到指定的服务器，并将服务器的响应显示在界面上。

Procession::Procession(int userid,QWidget *parent) : QWidget(parent), ui(new Ui::Procession), userid(userid){ ui->setupUi(this); processionWidget(); networkManager = new QNetworkAccessManager(this); // 初始化 networkManager 对象 connect(ui->connectServerBtn,&QPushButton::clicked,this,={ ui->message->setText('正在连接中……'); this->connectToServer(); }); connect(networkManager, &QNetworkAccessManager::finished, this, &Procession::handleServerResponse);

}

Procession::~Procession(){ delete ui;}

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::connectToServer(){ QJsonObject json; json['userid'] = this->userid;

QJsonDocument doc(json);    QByteArray postData = doc.toJson();

QNetworkRequest request(QUrl(ui->serverIP->text()));    request.setHeader(QNetworkRequest::ContentTypeHeader, 'application/json');

networkManager->post(request, postData);}

void Procession::handleServerResponse(QNetworkReply *reply){ if (reply->error() == QNetworkReply::NoError) { QByteArray response = reply->readAll(); ui->message->append(response); } else { ui->message->append('连接失败！'); }

    reply->deleteLater();}

服务器代码 (server.c)c#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sqlite3.h>#include <stdbool.h>#include <unistd.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <json-c/json.h>

#define DATABASE 'database.db'#define PORT 8080

struct Status { int sid; // 状态ID int uid; // 用户ID char device_name[10]; // 设备名称 char device_state[10]; // 设备状态 char value[10]; // 值 char mode[10]; // 模式};

void handleClientRequest(int clientSocket); // 处理客户端请求void handleTemperatureHumidity(int clientSocket, int uid); // 处理温度湿度请求void sendResponse(int clientSocket, const char* response); // 发送响应char* getAdvice(int temperature, int humidity); // 获取建议

int main() { int serverSocket, clientSocket; struct sockaddr_in serverAddress, clientAddress; socklen_t clientAddressLength = sizeof(clientAddress);

// 创建套接字    serverSocket = socket(AF_INET, SOCK_STREAM, 0);    if (serverSocket < 0) {        perror('创建套接字出错');        exit(1);    }

// 设置服务器地址    serverAddress.sin_family = AF_INET;    serverAddress.sin_addr.s_addr = INADDR_ANY;    serverAddress.sin_port = htons(PORT);

// 将套接字绑定到指定的地址和端口    if (bind(serverSocket, (struct sockaddr*)&serverAddress, sizeof(serverAddress)) < 0) {        perror('绑定套接字出错');        exit(1);    }

// 监听传入连接    if (listen(serverSocket, 5) < 0) {        perror('监听连接出错');        exit(1);    }

printf('服务器已启动。正在监听端口 %d...

', PORT);

while (true) {        // 接受客户端连接        clientSocket = accept(serverSocket, (struct sockaddr*)&clientAddress, &clientAddressLength);        if (clientSocket < 0) {            perror('接受连接出错');            exit(1);        }

    printf('客户端已连接，来自 %s:%d

', inet_ntoa(clientAddress.sin_addr), ntohs(clientAddress.sin_port));

    // 处理客户端请求        handleClientRequest(clientSocket);

    // 关闭客户端连接        close(clientSocket);        printf('客户端已断开连接

'); }

// 关闭服务器套接字    close(serverSocket);

return 0;}

void handleClientRequest(int clientSocket) { char buffer[1024]; int bytesRead = read(clientSocket, buffer, sizeof(buffer)); if (bytesRead < 0) { perror('从套接字读取数据出错'); exit(1); }

// 解析JSON请求    struct json_object* jsonRequest = json_tokener_parse(buffer);    if (jsonRequest == NULL) {        perror('解析JSON出错');        exit(1);    }

// 从JSON请求中获取用户ID    struct json_object* jsonUserID;    json_object_object_get_ex(jsonRequest, 'userid', &jsonUserID);    int uid = json_object_get_int(jsonUserID);

// 处理温度湿度请求    handleTemperatureHumidity(clientSocket, uid);

// 清理资源    json_object_put(jsonRequest);}

void handleTemperatureHumidity(int clientSocket, int uid) { sqlite3* db; int rc = sqlite3_open(DATABASE, &db); if (rc != SQLITE_OK) { perror('打开数据库出错'); exit(1); }

char query[100];    snprintf(query, sizeof(query), 'SELECT * FROM Status WHERE uid = %d', uid);

sqlite3_stmt* stmt;    rc = sqlite3_prepare_v2(db, query, -1, &stmt, 0);    if (rc != SQLITE_OK) {        perror('准备SQL语句出错');        exit(1);    }

// 获取用户的最新温度和湿度值    int temperature = 0;    int humidity = 0;

while (sqlite3_step(stmt) == SQLITE_ROW) {        struct Status status;        status.sid = sqlite3_column_int(stmt, 0);        status.uid = sqlite3_column_int(stmt, 1);        strcpy(status.device_name, (char*)sqlite3_column_text(stmt, 2));        strcpy(status.device_state, (char*)sqlite3_column_text(stmt, 3));        strcpy(status.value, (char*)sqlite3_column_text(stmt, 4));        strcpy(status.mode, (char*)sqlite3_column_text(stmt, 5));

    if (strcmp(status.device_name, 'Temperature') == 0) {            temperature = atoi(status.value);        } else if (strcmp(status.device_name, 'Humidity') == 0) {            humidity = atoi(status.value);        }    }

// 根据温度和湿度值获取建议    char* advice = getAdvice(temperature, humidity);

// 将建议发送给客户端    sendResponse(clientSocket, advice);

// 清理资源    sqlite3_finalize(stmt);    sqlite3_close(db);}

void sendResponse(int clientSocket, const char* response) { int bytesWritten = write(clientSocket, response, strlen(response)); if (bytesWritten < 0) { perror('写入套接字出错'); exit(1); }}

char* getAdvice(int temperature, int humidity) { char* advice = (char*)malloc(100);

if (temperature < 24) {        snprintf(advice, 100, '温度过低，请将温度调高至 26°C。');    } else if (humidity < 40 || humidity > 70) {        snprintf(advice, 100, '湿度过高或过低，请调整湿度水平。');    } else {        snprintf(advice, 100, '暂无建议。');    }

return advice;}

数据库设计

数据库名为 database.db，使用SQLite数据库。数据库中包含一个名为 Status 的表，用于存储用户的温湿度数据。表结构如下：

| 字段名 | 数据类型 | 描述 ||---|---|---|| sid | INTEGER | 状态ID (主键) || uid | INTEGER | 用户ID || device_name | TEXT | 设备名称 (例如：Temperature, Humidity) || device_state | TEXT | 设备状态 (例如：ON, OFF) || value | TEXT | 值 (例如：25, 60) || mode | TEXT | 模式 (例如：AUTO, MANUAL) |

总结

本文介绍了如何使用Qt框架构建一个简单的客户端程序，通过网络与C++服务器进行通信，并使用JSON格式进行数据交互。服务器程序使用SQLite数据库存储用户的温湿度数据，并根据客户端请求返回相应的建议。

关键词

Qt, C++, 网络通信, JSON, 服务器, 客户端, 数据库, 温湿度, 建