Qt网络编程：与服务器通信并获取JSON响应

Qt网络编程：与服务器通信并获取JSON响应

这篇文章将介绍如何使用Qt框架进行网络编程，并通过一个简单的示例演示如何实现与服务器的通信。

1. 项目背景

在这个示例中，我们将创建一个简单的Qt Widgets应用程序，它可以：

• 将用户ID发送到服务器。* 从服务器接收JSON格式的响应。* 将服务器的响应显示在界面上。

2. 客户端实现 (Qt)

2.1 头文件 procession.hcpp#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();

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

private: void processionWidget(); // 初始化界面

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

#endif // PROCESSION_H

2.2 源文件 procession.cppcpp#include 'procession.h'#include 'ui_procession.h'#include #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('http://localhost:8080'));    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();}

3. 服务器端实现 (C++)

以下是一个简单的C++服务器端代码示例，使用SQLite数据库和json-c库：cpp#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>#include 'server.h'

#define DATABASE 'database.db'

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) { 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