Qt5.8 (2).Java与Qt通信之TCP图片传输

Java-Qt-TCP数据传输

1. 程序描述

使用Qt建立TCP Server，用Java建立TCP Client，Client发送本地图片文件给Server，Server端使用Qt的QPixmap类显示在QLabel实例的背景中。

2. 核心代码

• Java端
  Main.java

import java.io.*;
import java.net.Socket;

public class Main {

    public static void main(String[] args) {

        Socket s;
        File sendFile = new File("F:/Image/test8.png");
        long fileSize = sendFile.length();

        if(!sendFile.exists()) {
            System.out.println("Cannot find the file");
            return;
        }


        //定义文件输入流，用于打开、读取文件
        FileInputStream fileInputStream = null;
        try {
            fileInputStream = new FileInputStream(sendFile);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

        //使用OutputStream向Socket发送数据
        OutputStream outputStream = null;
        //使用InputStream从Socket接收数据
        InputStream inputStream = null;

        /*建立客户端，连接服务器*/
        try {
            s = new Socket("127.0.0.1", 8899);
            outputStream = s.getOutputStream();

            int size = 0;
            byte[] buffer = new byte[(int) fileSize];

            while((size = fileInputStream.read(buffer)) != -1) {
                System.out.println("Data size: \t" + size);
                outputStream.write(buffer, 0, size);
                outputStream.flush();
            }

            //接收服务器反馈信息,等待数据传输结果确认
            while(true) {
                inputStream = s.getInputStream();
                InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
                BufferedReader br = new BufferedReader(inputStreamReader);
                  String str = br.readLine();
                  System.out.println("Server: \t" + str);
                  /*不能使用 (str == "ok") 判断，因为str是String类型的，
                  "ok"是字符串数组，直接用==进行比较是不相等的*/
                  if (str.equals("ok")) {
                      break;
                  }
              }
          } catch (IOException e) {
              System.out.println("Cannot connect the Server.");
              e.printStackTrace();
          }
      }
  }

• Qt端
  mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include 
// 2.添加头文件
#include 
#include 

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

// 4.添加信号槽
public slots:
    void slotNewConnection();
    void slotReceiveData();
    void slotSocketDisconnect();

private slots:
    void on_startServerBtn_clicked();

private:
    Ui::MainWindow *ui;
    // 3.添加成员 TCP Server和TCP Socket
    QTcpServer *myServer;
    QTcpSocket *mySocket;

};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include 
#include 

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    //初始化GUI组件
    ui->imgShowLabel->setScaledContents(true);
}

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

void MainWindow::on_startServerBtn_clicked()
{
    //5.按钮事件
    ui->startServerBtn->setText("Listening...");
    ui->startServerBtn->setEnabled(false);

    this->myServer = new QTcpServer(this);
    this->myServer->listen(QHostAddress::Any, 8899);

    //连接myServer的newConnection()信号与MainWindow的槽函数slotNewConnection()
    connect(this->myServer, SIGNAL(newConnection()), this, SLOT(slotNewConnection()));

}

void MainWindow::slotNewConnection()
{
    //使用mySocket接收客户端连接(这里只允许考虑一个连接的情况)
    this->mySocket = this->myServer->nextPendingConnection();
    //更新GUI
    ui->startServerBtn->setText("Client Connected.");

    //监听socket连接状态,准备接收数据
    //连接信号与槽
    connect(this->mySocket, SIGNAL(readyRead()), this, SLOT(slotReceiveData()));
    connect(this->mySocket, SIGNAL(disconnected()), this, SLOT(slotSocketDisconnect()));

    //控制台输出"Client connected success."
    qDebug()<<"Client connected success.";

}

void MainWindow::slotReceiveData()
{
    qDebug()<<"Start receive data from Client...";

    QByteArray bytes = NULL;
    while(this->mySocket->waitForReadyRead(100))
    {
        qDebug()<<"Data receiving...";
        bytes.append(this->mySocket->readAll());
    }

    //Send Back Data to Client
    if(this->mySocket->isWritable())
    {
        //结尾中的'\n'表示数据发送完毕
        QString sendData = "ok\n" ;
        this->mySocket->write(sendData.toStdString().c_str(), strlen(sendData.toStdString().c_str()));
    }
    else
    {
        qDebug()<<"Cannot send back data to Client.";
    }


    QPixmap pixmap;
    pixmap.loadFromData(bytes);
    //显示到GUI中
    ui->imgShowLabel->setPixmap(pixmap);

}

void MainWindow::slotSocketDisconnect()
{
    this->mySocket->close();
    ui->startServerBtn->setText("Listening...");
    qDebug()<<"Socket disconnected";
}

GUI展示

Qt端初始化GUI

Qt端建立TCP Server

Java端图片大小与服务器端接收确认

Qt端接收到图片并显示

参考

QPixmap支持的图片格式