Qt官方示例-TCP客户端/服务器示例

清疚 2023-06-23 14:26 101阅读 0赞

> 该示例演示了在本地主机上的**TCP客户端和服务器**是如何通讯的。

![demo.gif][]

## 客户端 ##

绑定信号槽。

connect(&tcpClient, &QAbstractSocket::connected, this, &Dialog::startTransfer); /* 连接到服务器时回送消息给服务器 */
    connect(&tcpClient, &QIODevice::bytesWritten,
            this, &Dialog::updateClientProgress); /* 绑定写数据到服务器的信号槽 */

连接到服务器。

tcpClient.connectToHost(QHostAddress::LocalHost, tcpServer.serverPort());

这里比较有意思的是，客户端连接到服务器->客户端(tcpClient)触发startTransfer槽函数->调用`tcpClient.write`\->触发`QIODevice::bytesWritten`信号->触发updateClientProgress槽函数调用->就一直`tcpClient.write`，直到if条件不成立后后停止发送。

void Dialog::startTransfer()
    { 
        // called when the TCP client connected to the loopback server
        bytesToWrite = TotalBytes - int(tcpClient.write(QByteArray(PayloadSize, '@')));
        clientStatusLabel->setText(tr("Connected"));
    }

void Dialog::updateClientProgress(qint64 numBytes)
    { 
        // called when the TCP client has written some bytes
        bytesWritten += int(numBytes);
    
        // only write more if not finished and when the Qt write buffer is below a certain size.
        if (bytesToWrite > 0 && tcpClient.bytesToWrite() <= 4 * PayloadSize) /* 直到if条件不成立后后停止发送 */
            bytesToWrite -= tcpClient.write(QByteArray(qMin(bytesToWrite, PayloadSize), '@'));
    
        clientProgressBar->setMaximum(TotalBytes);
        clientProgressBar->setValue(bytesWritten);
        clientStatusLabel->setText(tr("Sent %1MB").arg(bytesWritten / (1024 * 1024)));
    }

## 服务端 ##

绑定信号槽用于新连接：

connect(&tcpServer, &QTcpServer::newConnection,
            this, &Dialog::acceptConnection);

监听客户端连接。

!tcpServer.isListening() && !tcpServer.listen()

服务端新连接到来：

void Dialog::acceptConnection()
    { 
        tcpServerConnection = tcpServer.nextPendingConnection();
        if (!tcpServerConnection) { 
            serverStatusLabel->setText(tr("Error: got invalid pending connection!"));
            return;
        }
    
        connect(tcpServerConnection, 
                &QIODevice::readyRead,
                this, 
                &Dialog::updateServerProgress); /* 接受客户端数据的槽函数 */
        connect(tcpServerConnection,
                QOverload<QAbstractSocket::SocketError>::of(&QAbstractSocket::error),
                this, 
                &Dialog::displayError); /* 错误反馈 */
        connect(tcpServerConnection, 
                &QTcpSocket::disconnected,
                tcpServerConnection, 
                &QTcpSocket::deleteLater); /* 断开反馈 */
    
        serverStatusLabel->setText(tr("Accepted connection"));
        tcpServer.close(); 
    }

接收来自客户端的数据：

void Dialog::updateServerProgress()
    { 
        bytesReceived += int(tcpServerConnection->bytesAvailable());
        tcpServerConnection->readAll(); /* 读数据 */
    
        serverProgressBar->setMaximum(TotalBytes);
        serverProgressBar->setValue(bytesReceived); /* 设置进度条 */
        serverStatusLabel->setText(tr("Received %1MB") /* 显示在界面上 */
                                   .arg(bytesReceived / (1024 * 1024)));
    
        if (bytesReceived == TotalBytes) { 
            tcpServerConnection->close();
            startButton->setEnabled(true);
    #ifndef QT_NO_CURSOR
            QApplication::restoreOverrideCursor();
    #endif
        }
    }

## 关于更多 ##

*  在**QtCreator软件**可以找到：

![what\_find.png][what_find.png]

*  或在以下**Qt安装目录**找到：

C:\Qt\{ 你的Qt版本}\Examples\{ 你的Qt版本}\network\loopback

*  **相关链接**

https://doc.qt.io/qt-5/qtnetwork-loopback-example.html

*  Qt君公众号回复『**Qt示例**』获取更多内容。

[demo.gif]: https://img-blog.csdnimg.cn/2019121921182822.gif
[what_find.png]: https://img-blog.csdnimg.cn/20191219210254626.png