該示例演示了在本地主機上的TCP客戶端和服務器是如何通訊的。

客戶端

綁定信號槽。

connect(&tcpClient, &QAbstractSocket::connected, this, &Dialog::startTransfer); /* 連接到服務器時回送消息給服務器 */ connect(&tcpClient, &QIODevice::bytesWritten,this, &Dialog::updateClientProgress); /* 綁定寫數據到服務器的信號槽 */

連接到服務器。

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

這里比較有意思的是，客戶端連接到服務器->客戶端(tcpClient)觸發startTransfer槽函數->調用tcpClient.write->觸發QIODevice::bytesWritten信號->觸發updateClientProgress槽函數調用->就一直tcpClient.write，直到if條件不成立后后停止發送。

void Dialog::startTransfer() {// called when the TCP client connected to the loopback serverbytesToWrite = TotalBytes - int(tcpClient.write(QByteArray(PayloadSize, '@')));clientStatusLabel->setText(tr("Connected")); } void Dialog::updateClientProgress(qint64 numBytes) {// called when the TCP client has written some bytesbytesWritten += 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條件不成立后后停止發送 */bytesToWrite -= tcpClient.write(QByteArray(qMin(bytesToWrite, PayloadSize), '@'));clientProgressBar->setMaximum(TotalBytes);clientProgressBar->setValue(bytesWritten);clientStatusLabel->setText(tr("Sent %1MB").arg(bytesWritten / (1024 * 1024))); }

服務端

綁定信號槽用于新連接：

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

監聽客戶端連接。

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

服務端新連接到來：

void Dialog::acceptConnection() {tcpServerConnection = tcpServer.nextPendingConnection();if (!tcpServerConnection) {serverStatusLabel->setText(tr("Error: got invalid pending connection!"));return;}connect(tcpServerConnection, &QIODevice::readyRead,this, &Dialog::updateServerProgress); /* 接受客戶端數據的槽函數 */connect(tcpServerConnection,QOverload<QAbstractSocket::SocketError>::of(&QAbstractSocket::error),this, &Dialog::displayError); /* 錯誤反饋 */connect(tcpServerConnection, &QTcpSocket::disconnected,tcpServerConnection, &QTcpSocket::deleteLater); /* 斷開反饋 */serverStatusLabel->setText(tr("Accepted connection"));tcpServer.close(); }

接收來自客戶端的數據：

void Dialog::updateServerProgress() {bytesReceived += int(tcpServerConnection->bytesAvailable());tcpServerConnection->readAll(); /* 讀數據 */serverProgressBar->setMaximum(TotalBytes);serverProgressBar->setValue(bytesReceived); /* 設置進度條 */serverStatusLabel->setText(tr("Received %1MB") /* 顯示在界面上 */.arg(bytesReceived / (1024 * 1024)));if (bytesReceived == TotalBytes) {tcpServerConnection->close();startButton->setEnabled(true); #ifndef QT_NO_CURSORQApplication::restoreOverrideCursor(); #endif} }

關于更多

• 在QtCreator軟件可以找到：

• 或在以下Qt安裝目錄找到：

C:Qt{你的Qt版本}Examples{你的Qt版本}networkloopback

• 相關鏈接

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

• Qt君公眾號回復『Qt示例』獲取更多內容。

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