QT客户端和Linux服务器如何连接

Question

不能连接怎么解决呢

服务器：

// main.c

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "server.h"

#define PORT 8989

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...\n", 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\n", 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\n");
    }

    // 关闭服务器套接字
    close(serverSocket);

    return 0;
}
===================================================================================================
// server.h

#ifndef SERVER_H
#define SERVER_H

#include <json-c/json.h>

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

#endif
===========================

// server.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>
#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;
}

客户端

#ifndef PROCESSION_H
#define PROCESSION_H

#include <QWidget>
#include <QNetworkAccessManager>
#include <QNetworkReply>

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

#include "procession.h"
#include "ui_procession.h"
#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonArray>
#include <QDebug>

//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();
}

Answer 1

你可以在连接失败那行那里打印错误信息：

qDebug() << "Error message:" << reply->errorString();

根据输出的错误信息可以大概知道连接失败的原因，再进行解决