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TCP通信概述

? ?TCP(Transmission Control Protocol)是一種被大多數 Internet 網絡協議(如 HTTP 和 FTP)用于 數據傳輸的低級網絡協議，它是可靠的、面向流、面向連接的傳輸協議，特別適合用于連續數據傳輸。

? ?TCP通信必須先建立TCP連接，通信端分為客戶端和服務器端。

? ?Qt提供 QTcpSocket類和QTcpServer類用于建立TCP通信應用程 TCP Client 序。

? ?服務器端程序必須使用QTcpServer用于端口監聽,建 立服務器;

? ?QTcpSocket用于建立連接后使用套接字(Socket) 進行通信。

? ?QTcpServer是從QObject繼承的類，它主要用于服務器端建立網絡監聽，創建網絡Socket連 接。QTcpServer類的主要接口函數見表

• void close()

  • 關閉服務器，停止網絡監聽

• bool listen()

  • 在給定IP地址和端口上開始監聽，若成功就返回true

• bool isListening()

  • 返回true表示服務器處于監聽狀態

• QTcpSocket * nextPendingConnection()

  • 返回下一個等待接入的連接

• QHostAddress serverAddress()

  • 如果服務器處于監聽狀態，返回服務器地址

• quint 16 serverPort()

  • 如果服務器處于監聽狀態，返回服務器監聽端口

• bool waitForNewConnection()

  • 以阻塞方式等待新的連接 信號

• void acceptError( QAbstractSocket::SocketError socketError)

  • 當接受一個新的連接發生錯誤時發射此信號，參數 socketError描述了錯誤信息

• void newConnection()

  • ?當有新的連接時發射此信號

• void incomingConnection(qintptr socketDescriptor)

  • 當有一個新的連接可用時，QTcpServer內部調用此函數，創 建一個QTcpSocket對象，添加到內部可用新連接列表，然 后發射newConnection()信號。用戶若從QTcpServer繼承定 義類，可以重定義此函數，但必須調用 addPendingConnection()

• void addPendingConnection(QTcpSocket ?socket)

  • 由 incomingConnection()調用，將創建的 QTcpSocket 添加到 內部新可用連接列表

?? ?服務器端程序首先需要用QTcpServendisten()開始服務器端監聽，可以指定監聽的IP地址和 端口，一般一個服務程序只監聽某個端口的網絡連接。

?? ?當有新的客戶端接入時，QTcpServer內部的incomingConnection()函數會創建一個與客戶端連 接的QTcpSocket對象，然后發射信號newConnection()。在newConnection()信號的槽函數中，可以用nextPendingConnection()接受客戶端的連接，然后使用QTcpSocket與客戶端通信。?? ??? ?

?? ?所以在客戶端與服務器建立TCP連接后，具體的數據通信是通過QTcpSocket完成的。QTcpSocket類提供了 TCP協議的接口，可以用QTcpSocket類實現標準的網絡通信協議如POP3、 SMTP和NNTP,也可以設計自定義協議。?

?? ?QTcpSocket是從QIODevice間接繼承的類，所以具有流讀寫的功能

?? ?

QTcpSocket類除了構造函數和析構函數，其他函數都是從QAbstractSocket繼承或重定義的。QAbstractSocket用于TCP通信的主要接口函數見表

• void connectToHost(QHostAddress?&address, quint 16 port,)

  • 以異步方式連接到指定IP地址和端口的TCP服務器，連接成功? 后會發射connected()信號

• void disconnectFromHost()

  • 斷開socket，關閉成功后發射disconnected()信號

• bool waitForConnected()

  • 等待直到建立socket連接

• bool waitForDisconnected()

  • 等待直到斷開socket連接

• QHostAddress localAddress()

  • 返回本socket的地址

• quint 16 localPort()

  • 返回本socket的端口

• QHostAddress peerAddress()

  • 在已連接狀態下，返回對方socket的地址

• QString peerName()

  • 返回connectToHost()連接到的對方的主機名

• quintl6 peerPort()

  • 在已連接狀態下，返回對方socket的端口

• qint64 readBufferSize()

  • 返回內部讀取緩沖區的大小，該大小決定了 read()和 readAII()函數能讀出的數據的大小

• void setReadBufferSize(qint64 size)

  • 設置內部讀取緩沖區大小

• qint64 bytesAvailable()

  • 返回需要讀取的緩沖區的數據的字節數

• bool canReadLine()

  • 如果有行數據要從socket緩沖區讀取，就返回true

• SocketState state()

  • 返回socket當前的狀態

• void connected()

  • connectToHost()成功連接到服務器后發射此信號

• void disconnected()

  • 當socket斷開連接后發射此信號

• void error(QAbstractSocket::SocketError socketError)

  • 當socket發生錯誤時發射此信號

• void hostFound()

  • 調用connectToHost()找到主機后發射此信號

• void stateChanged(QAbstractSocket::SocketState socketState)

  • 當 socket的狀態變化時發射此信號，參數socketState表示了socket 當前的狀態

• void readyRead()

  • 當緩沖區有新數據需要讀取時發射此信號，在此信號的槽函數里 讀取緩沖區的數據

?? ?TCP客戶端使用QTcpSocket與TCP服務器建立連接并通信

?? ?客戶端的QTcpSocket實例首先通過connectToHost()嘗試連接到服務器，需要指定服務器的IP地址和端口.connectToHost()是異步方式連接服務器，不會阻塞程序運行，連接后發射connected()信號。

?? ?如果需要使用阻塞方式連接服務器，則使用waitForConnected()函數阻塞程序運行，直到連接 成功或失敗。例如：?

socket->connectToHost("192.168.1.100", 1340); if (socket->waitForConnected(1000)) qDebug("Connected!");

?? ?與服務器端建立socket連接后，就可以向緩沖區寫數據或從接收緩沖區讀取數據，實現數據的通信。當緩沖區有新數據進入時，會發射readyRead()信號，一般在此信號的槽函數里讀取緩沖區數據。

?? ?QTcpSocket是從QIODevice間接繼承的，所以可以使用流數據讀寫功能。—個QTcpSocket 實例既可以接收數據也可以發送數據，且接收與發射是異步工作的，有各自的緩沖區。?

?? ?作為演示TCP通信的實例，創建了一個TCPClient程序和一個TCPServer程序

TCPServer程序具有如下的功能：?

?? ??根據指定IP地址(本機地址)和端口打開網絡監聽，有客戶端連接時創建socket連接;?

?? ??采用基于行的數據通信協議，可以接收客戶端發來的消息，也可以向客戶端發送消息；?

?? ??在狀態欄顯示服務器監聽狀態和socket的狀態。?

頭文件

#pragma once#include #include "Ui_QGuiTcpServer.h"#include #include #include class QGuiTcpServer : public QMainWindow{ Q_OBJECTpublic: QGuiTcpServer(QWidget *parent = Q_NULLPTR); ~QGuiTcpServer();private slots: void actStart_triggered();//開始監聽 void actStop_triggered(); void actHostInfo_triggered(); void actClear_triggered(); void btnSend_clicked(); void onNewConnection(); void onSocketStateChange(QAbstractSocket::SocketState socketState); void onClientConnected(); //Client Socket connected void onClientDisconnected();//Client Socket disconnected void onSocketReadyRead();//讀取socket傳入的數據private: Ui::QTcpServer ui;protected: void closeEvent(QCloseEvent* event);private: QLabel* m_pLabListen;//狀態欄標簽 QLabel* m_pLabSocketState;//狀態欄標簽 QTcpServer* m_pTcpServer;//tcp服務器 QTcpSocket* m_pTcpSocket;//tcp通信的Socket QString getLocalIP();//獲取本機IP地址};

源文件

#include "QGuiTcpServer.h"#include #include #pragma execution_character_set("utf-8")QGuiTcpServer::QGuiTcpServer(QWidget *parent) : QMainWindow(parent){ ui.setupUi(this); m_pLabListen = new QLabel("監聽狀態："); m_pLabListen->setMinimumWidth(150); ui.statusBar->addWidget(m_pLabListen); m_pLabSocketState = new QLabel("狀態："); m_pLabSocketState->setMinimumWidth(200); ui.statusBar->addWidget(m_pLabSocketState); QString localIP = getLocalIP();//本機IP setWindowTitle(windowTitle() + "----本機IP：" + localIP); ui.comboIP->addItem(localIP); m_pTcpServer = new QTcpServer(this); connect(m_pTcpServer, SIGNAL(newConnection()), this, SLOT(onNewConnection())); connect(ui.actStart, SIGNAL(triggered()), this, SLOT(actStart_triggered())); connect(ui.actStop, SIGNAL(triggered()), this, SLOT(actStop_triggered())); connect(ui.actHostInfo, SIGNAL(triggered()), this, SLOT(actHostInfo_triggered())); connect(ui.actClear, SIGNAL(triggered()), this, SLOT(actClear_triggered())); connect(ui.btnSend, SIGNAL(clicked()), this, SLOT(btnSend_clicked()));}QGuiTcpServer::~QGuiTcpServer(){}//開始監聽void QGuiTcpServer::actStart_triggered(){ QString IP = ui.comboIP->currentText();//IP地址 quint16 port = ui.spinPort->value();//端口 QHostAddress addr(IP); m_pTcpServer->listen(addr, port);// //m_pLabListen->listen(QHostAddress::LocalHost,port);// Equivalent to QHostAddress("127.0.0.1"). ui.plainTextEdit->appendPlainText("**開始監聽..."); ui.plainTextEdit->appendPlainText("**服務器地址："+ m_pTcpServer->serverAddress().toString()); ui.plainTextEdit->appendPlainText("**服務器端口："+ QString::number(m_pTcpServer->serverPort())); ui.actStart->setEnabled(false); ui.actStop->setEnabled(true); m_pLabListen->setText("監聽狀態：正在監聽");}void QGuiTcpServer::actStop_triggered(){ if (m_pTcpServer->isListening()) //tcpServer正在監聽 { m_pTcpServer->close();//停止監聽 ui.actStart->setEnabled(true); ui.actStop->setEnabled(false); m_pLabListen->setText("監聽狀態：已停止監聽"); }}void QGuiTcpServer::actHostInfo_triggered(){ QString hostName = QHostInfo::localHostName();//本地主機名 ui.plainTextEdit->appendPlainText("本機主機名：" + hostName + "\n"); QHostInfo hostInfo = QHostInfo::fromName(hostName); QList addList = hostInfo.addresses();// if (!addList.isEmpty()) { for (int i = 0; i < addList.count(); i++) { QHostAddress aHost = addList.at(i); if (QAbstractSocket::IPv4Protocol == aHost.protocol()) { QString IP = aHost.toString(); ui.plainTextEdit->appendPlainText("本機IP地址：" + aHost.toString()); if (ui.comboIP->findText(IP) < 0) ui.comboIP->addItem(IP); } } }}void QGuiTcpServer::actClear_triggered(){ ui.plainTextEdit->clear();}void QGuiTcpServer::btnSend_clicked(){ QString msg = ui.editMsg->text(); ui.plainTextEdit->appendPlainText("[out] " + msg); ui.editMsg->clear(); ui.editMsg->setFocus(); QByteArray str = msg.toUtf8(); str.append('\n');//添加一個換行符 m_pTcpSocket->write(str);}void QGuiTcpServer::onNewConnection(){ m_pTcpSocket = m_pTcpServer->nextPendingConnection(); //創建socket connect(m_pTcpSocket, SIGNAL(connected()), this, SLOT(onClientConnected())); onClientConnected(); connect(m_pTcpSocket, SIGNAL(disconnected()), this, SLOT(onClientDisconnected())); connect(m_pTcpSocket, SIGNAL(stateChanged(QAbstractSocket::SocketState)), this, SLOT(onSocketStateChange(QAbstractSocket::SocketState))); onSocketStateChange(m_pTcpSocket->state()); connect(m_pTcpSocket, SIGNAL(readyRead()), this, SLOT(onSocketReadyRead()));}void QGuiTcpServer::onSocketStateChange(QAbstractSocket::SocketState socketState){ switch (socketState) { case QAbstractSocket::UnconnectedState: m_pLabSocketState->setText("scoket狀態：UnconnectedState"); break; case QAbstractSocket::HostLookupState: m_pLabSocketState->setText("scoket狀態：HostLookupState"); break; case QAbstractSocket::ConnectingState: m_pLabSocketState->setText("scoket狀態：ConnectingState"); break; case QAbstractSocket::ConnectedState: m_pLabSocketState->setText("scoket狀態：ConnectedState"); break; case QAbstractSocket::BoundState: m_pLabSocketState->setText("scoket狀態：BoundState"); break; case QAbstractSocket::ClosingState: m_pLabSocketState->setText("scoket狀態：ClosingState"); break; case QAbstractSocket::ListeningState: m_pLabSocketState->setText("scoket狀態：ListeningState"); }}//客戶端接入時void QGuiTcpServer::onClientConnected(){ ui.plainTextEdit->appendPlainText("**client socket connected"); ui.plainTextEdit->appendPlainText("**peer address:" + m_pTcpSocket->peerAddress().toString()); ui.plainTextEdit->appendPlainText("**peer port:" + QString::number(m_pTcpSocket->peerPort()));}//客戶端斷開連接時void QGuiTcpServer::onClientDisconnected(){ ui.plainTextEdit->appendPlainText("**client socket disconnected"); m_pTcpSocket->deleteLater();}//讀取緩沖區行文本void QGuiTcpServer::onSocketReadyRead(){ while (m_pTcpSocket->canReadLine()) ui.plainTextEdit->appendPlainText("[in] " + m_pTcpSocket->readLine());}//關閉窗口時停止監聽void QGuiTcpServer::closeEvent(QCloseEvent* event){ if (m_pTcpServer->isListening()) m_pTcpServer->close();;//停止網絡監聽 event->accept();}//獲取本機IP地址QString QGuiTcpServer::getLocalIP(){ QString hostName = QHostInfo::localHostName();//本機主機名 QHostInfo hostInfo = QHostInfo::fromName(hostName); QString localIP = ""; QList addList = hostInfo.addresses();// if (!addList.isEmpty()) { for (int i = 0; i < addList.count(); i++) { QHostAddress aHost = addList.at(i); if (QAbstractSocket::IPv4Protocol == aHost.protocol()) { localIP = aHost.toString(); break; } } } return localIP;}

TCPClient程序程序具有如下的功能：

?? ??通過IP地址和端口號連接到服務器；?

?? ??采用基于行的數據通信協議，與服務器端收發消息：?

?? ??處理QTcpSocket的StateChange()信號，在狀態欄顯示socket的狀態。

頭文件

#pragma once#include #include "ui_QGuiTcpClient.h"#include #include class QGuiTcpClient : public QMainWindow{ Q_OBJECTpublic: QGuiTcpClient(QWidget *parent = Q_NULLPTR); ~QGuiTcpClient();private slots: //自定義槽函數 void onConnected(); void onDisconnected(); void onSocketStateChange(QAbstractSocket::SocketState socketState); void onSocketReadyRead();//讀取socket傳入的數據 void actConnect_triggered(); void actDisconnect_triggered(); void actClear_triggered(); void btnSend_clicked();private: Ui::QGuiTcpClient ui;protected: void closeEvent(QCloseEvent* event);private: QTcpSocket* m_pTcpClient; //socket QLabel* m_pLabSocketState;//狀態欄標簽 QString getLocalIP();//獲取本機IP地址};

源文件

#include "QGuiTcpClient.h"#include #include #pragma execution_character_set("utf-8")QGuiTcpClient::QGuiTcpClient(QWidget* parent) : QMainWindow(parent){ ui.setupUi(this); m_pTcpClient = new QTcpSocket(this); //創建socket變量 m_pLabSocketState = new QLabel("Socket狀態：");//狀態欄標簽 m_pLabSocketState->setMinimumWidth(250); ui.statusBar->addWidget(m_pLabSocketState); QString localIP = getLocalIP();//本機IP this->setWindowTitle(this->windowTitle() + "----本機IP：" + localIP); ui.comboServer->addItem(localIP); connect(m_pTcpClient, SIGNAL(connected()), this, SLOT(onConnected())); connect(m_pTcpClient, SIGNAL(disconnected()), this, SLOT(onDisconnected())); connect(m_pTcpClient, SIGNAL(stateChanged(QAbstractSocket::SocketState)), this, SLOT(onSocketStateChange(QAbstractSocket::SocketState))); connect(m_pTcpClient, SIGNAL(readyRead()), this, SLOT(onSocketReadyRead())); connect(ui.actConnect, SIGNAL(triggered()), this, SLOT(actConnect_triggered())); connect(ui.actDisconnect, SIGNAL(triggered()), this, SLOT(actDisconnect_triggered())); connect(ui.actClear, SIGNAL(triggered()), this, SLOT(actClear_triggered())); connect(ui.btnSend, SIGNAL(clicked()), this, SLOT(btnSend_clicked()));}QGuiTcpClient::~QGuiTcpClient(){}void QGuiTcpClient::onConnected(){ ui.plainTextEdit->appendPlainText("**已連接到服務器"); ui.plainTextEdit->appendPlainText("**peer address:" + m_pTcpClient->peerAddress().toString()); ui.plainTextEdit->appendPlainText("**peer port:" + QString::number(m_pTcpClient->peerPort())); ui.actConnect->setEnabled(false); ui.actDisconnect->setEnabled(true);}void QGuiTcpClient::onDisconnected(){ ui.plainTextEdit->appendPlainText("**已斷開與服務器的連接"); ui.actConnect->setEnabled(true); ui.actDisconnect->setEnabled(false);}void QGuiTcpClient::onSocketStateChange(QAbstractSocket::SocketState socketState){ switch (socketState) { case QAbstractSocket::UnconnectedState: m_pLabSocketState->setText("scoket狀態：UnconnectedState"); break; case QAbstractSocket::HostLookupState: m_pLabSocketState->setText("scoket狀態：HostLookupState"); break; case QAbstractSocket::ConnectingState: m_pLabSocketState->setText("scoket狀態：ConnectingState"); break; case QAbstractSocket::ConnectedState: m_pLabSocketState->setText("scoket狀態：ConnectedState"); break; case QAbstractSocket::BoundState: m_pLabSocketState->setText("scoket狀態：BoundState"); break; case QAbstractSocket::ClosingState: m_pLabSocketState->setText("scoket狀態：ClosingState"); break; case QAbstractSocket::ListeningState: m_pLabSocketState->setText("scoket狀態：ListeningState"); }}void QGuiTcpClient::onSocketReadyRead(){ while (m_pTcpClient->canReadLine()) ui.plainTextEdit->appendPlainText("[in] " + m_pTcpClient->readLine());}void QGuiTcpClient::actConnect_triggered(){ QString addr = ui.comboServer->currentText(); quint16 port = ui.spinPort->value(); m_pTcpClient->connectToHost(addr, port);}void QGuiTcpClient::actDisconnect_triggered(){ if (m_pTcpClient->state() == QAbstractSocket::ConnectedState) m_pTcpClient->disconnectFromHost();}void QGuiTcpClient::actClear_triggered(){ ui.plainTextEdit->clear();}void QGuiTcpClient::btnSend_clicked(){ QString msg = ui.editMsg->text(); ui.plainTextEdit->appendPlainText("[out] " + msg); ui.editMsg->clear(); ui.editMsg->setFocus(); QByteArray str = msg.toUtf8(); str.append('\n'); m_pTcpClient->write(str);}void QGuiTcpClient::closeEvent(QCloseEvent* event){ if (m_pTcpClient->state() == QAbstractSocket::ConnectedState) m_pTcpClient->disconnectFromHost(); event->accept();}QString QGuiTcpClient::getLocalIP(){ QString hostName = QHostInfo::localHostName();//本地主機名 QHostInfo hostInfo = QHostInfo::fromName(hostName); QString localIP = ""; QList addList = hostInfo.addresses();// if (!addList.isEmpty()) { for (int i = 0; i < addList.count(); i++) { QHostAddress aHost = addList.at(i); if (QAbstractSocket::IPv4Protocol == aHost.protocol()) { localIP = aHost.toString(); break; } } } return localIP;}

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