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Qt 实现TCP通信和UDP通信

1、TCP通信

QT中实现TCP通信主要用到了以下类：QTcpServer、QTcpSocket、QHostAddress等；

• 使用QTcpServer来创建一个TCP服务器，在新的连接建立时，将新建立连接的socket添加到列表中，以便发送数据，同时监听在指定的IP地址和端口上，并在有新的客户端连接上来时进行处理；
• 使用QTcpSocket来创建一个TCP客户端，连接到服务器并发送数据；

示例代码：

（1）创建两个头文件(TcpServer.h 和 TcpClient.h)：

TcpServer.h

#ifndef TCPSERVER_H
#define TCPSERVER_H#include <QObject>
#include <QTcpServer>
#include <QTcpSocket>class TcpServer : public QObject
{Q_OBJECT
public:explicit TcpServer(QObject *parent = nullptr);signals:public slots:void startServer();void newClientConnection();void readData();void clientDisconnected();private:QTcpServer *tcpServer;QList<QTcpSocket *> clients;
};#endif // TCPSERVER_H

TcpClient.h

#ifndef TCPCLIENT_H
#define TCPCLIENT_H#include <QObject>
#include <QTcpSocket>class TcpClient : public QObject
{Q_OBJECT
public:explicit TcpClient(QObject *parent = nullptr);public slots:void onConnected();void onDisconnected();void onError(QAbstractSocket::SocketError error);void onReadyRead();void connectToServer(QString ipAddress, int port);void sendData(QByteArray data);private:QTcpSocket *socket;
};#endif // TCPCLIENT_H

（2）创建两个源文件(TcpServer.cpp 和 TcpClient.cpp)：

TcpServer.cpp

#include "tcpserver.h"
#include <QDebug>TcpServer::TcpServer(QObject *parent) : QObject(parent)
{
}void TcpServer::startServer()
{tcpServer = new QTcpServer(this);connect(tcpServer, SIGNAL(newConnection()), this, SLOT(newClientConnection()));if (!tcpServer->listen(QHostAddress::Any, 1234)){qDebug() << "Unable to start the server: " << tcpServer->errorString();return;}qDebug() << "Listening on " << QHostAddress::Any << ":" << "1234";
}void TcpServer::newClientConnection()
{while (tcpServer->hasPendingConnections()){QTcpSocket *client = tcpServer->nextPendingConnection();clients.push_back(client);QObject::connect(client, SIGNAL(readyRead()), this, SLOT(readData()));QObject::connect(client, SIGNAL(disconnected()), this, SLOT(clientDisconnected()));}
}void TcpServer::readData()
{QTcpSocket *sender = static_cast<QTcpSocket*>(QObject::sender());QByteArray data = sender->readAll();qDebug() << "Received: " << data;
}void TcpServer::clientDisconnected()
{QTcpSocket *sender = static_cast<QTcpSocket*>(QObject::sender());clients.removeOne(sender);sender->deleteLater();
}

TcpClient.cpp

#include "tcpclient.h"
#include <QDebug>TcpClient::TcpClient(QObject *parent) : QObject(parent)
{
}void TcpClient::connectToServer(QString ipAddress, int port)
{socket = new QTcpSocket(this);connect(socket, SIGNAL(connected()), this, SLOT(onConnected()));connect(socket, SIGNAL(disconnected()), this, SLOT(onDisconnected()));connect(socket, SIGNAL(error(QAbstractSocket::SocketError)), this, SLOT(onError(QAbstractSocket::SocketError)));connect(socket, SIGNAL(readyRead()), this, SLOT(onReadyRead()));socket->connectToHost(ipAddress, port);
}void TcpClient::sendData(QByteArray data)
{if (socket && socket->state() == QAbstractSocket::ConnectedState)socket->write(data);
}void TcpClient::onConnected()
{qDebug() << "Connected!";
}void TcpClient::onDisconnected()
{qDebug() << "Disconnected!";
}void TcpClient::onError(QAbstractSocket::SocketError error)
{qDebug() << "Error: " << socket->errorString();
}void TcpClient::onReadyRead()
{qDebug() << "Received: " << socket->readAll();
}

（3）TCP客户端与TCP服务端通信，打开main.cpp，添加头文件以及创建TcpServer对象和TcpClient对象：

main.cpp

#include <QCoreApplication>
#include "tcpserver.h"
#include "tcpclient.h"int main(int argc, char *argv[])
{QCoreApplication a(argc, argv);//创建服务器对象TcpServer server;server.startServer();//创建客户端对象TcpClient client;client.connectToServer("127.0.0.1", 1234);//发送数据client.sendData("Hello from client!");return a.exec();
}

2、UDP通信

QT中实现UDP通信主要用到了以下类：QUdpSocket、QHostAddress等；

• UdpServer是服务器端，用于监听客户端发送的消息并回复同样的消息；
• UdpClient是客户端，用于向服务器发送一条消息，并等待来自服务器的回复；

示例代码：

（1）创建两个头文件(UdpServer.h 和 UdpClient.h)：

UdpServer.h

UdpServer继承自QObject，该类包含私有成员变量QUdpSocket *udpSocket，start()函数用于启动服务器；

#ifndef UDPSERVER_H
#define UDPSERVER_H# 这两个头文件分别用于QObject基类和QUdpSocket类，前者提供Qt对象模型所需的大量工具和服务，后者用于UDP套接字支持
#include <QObject>
#include <QUdpSocket>class UdpServer : public QObject
{Q_OBJECT
public:explicit UdpServer(QObject *parent = nullptr);void start();signals:private:QUdpSocket *udpSocket;
};#endif // UDPSERVER_H

UdpClient.h

UdpClient同样继承自QObject，包含一个QUdpSocket指针udpSocket和一个send()函数用于向服务器发送消息；

#ifndef UDPCLIENT_H
#define UDPCLIENT_H#include <QObject>
#include <QUdpSocket>class UdpClient : public QObject
{Q_OBJECT
public:explicit UdpClient(QObject *parent = nullptr);void send(const QString &message);signals:private:QUdpSocket *udpSocket;
};#endif // UDPCLIENT_H

（2）创建两个源文件(UdpServer.cpp 和 UdpClient.cpp)：

UdpServer.cpp

UdpServer的实现文件中，首先在构造函数中创建了一个QUdpSocket对象udpSocket，该对象用于通信，start()函数则用于启动服务器，包括绑定端口和建立接收数据的连接：

• bind()函数用于将UDP套接字与IP地址和端口绑定，以便开始监听传入的消息；
• readyRead信号是QUdpSocket类的一个信号，这里使用connect()函数将其与另一个函数连接起来，该函数会在每次接收到数据时执行；

#include "UdpServer.h"
#include <QDebug>UdpServer::UdpServer(QObject *parent) : QObject(parent)
{udpSocket = new QUdpSocket(this);
}void UdpServer::start()
{quint16 port = 1234;if (udpSocket->bind(QHostAddress::AnyIPv4, port)){qDebug() << "UDP server is listening on port" << port;}else{qDebug() << "Failed to bind the UDP server to port" << port;}connect(udpSocket, &QUdpSocket::readyRead, this, [this](){while (udpSocket->hasPendingDatagrams()){QByteArray datagram;datagram.resize(udpSocket->pendingDatagramSize());udpSocket->readDatagram(datagram.data(), datagram.size());qDebug() << "Received from client:" << datagram;}});
}

UdpClient.cpp

UdpClient的实现文件中，同样在构造函数中创建了一个QUdpSocket对象udpSocket，用于通信，send()函数则用于向服务器发送消息：

• writeDatagram()函数用于将datagram指定的数据报发送到目标地址和端口；
• qDebug()函数用于输出日志信息，记录已发送至服务器的消息；

#include "UdpClient.h"
#include <QDebug>UdpClient::UdpClient(QObject *parent) : QObject(parent)
{udpSocket = new QUdpSocket(this);
}void UdpClient::send(const QString &message)
{QByteArray datagram = message.toUtf8();quint16 port = 1234;QHostAddress address("127.0.0.1");udpSocket->writeDatagram(datagram, address, port);qDebug() << "Sent to server:" << message;
}

（3）UDP客户端与UDP服务端通信，打开main.cpp，添加头文件以及创建UdpServer对象和UdpClient对象：

main.cpp

主函数主要是启动UdpServer和UdpClient，并向服务器发送一条消息：

• udpServer和udpClient是用于运行这两个对象的实例；
• send()函数发送了一条消息，该消息会被服务器接收并回复同样的消息；
• a.exec()函数开始Qt事件循环，直到程序退出为止；

#include <QCoreApplication>
#include "UdpServer.h"
#include "UdpClient.h"int main(int argc, char *argv[])
{QCoreApplication a(argc, argv);UdpServer udpServer;udpServer.start();UdpClient udpClient;udpClient.send("Hello from client!");return a.exec();
}

在Qt Creator中运行程序，可以看到以下输出：

UDP server is listening on port 1234
Sent to server: "Hello from client!"
Received from client: "Hello from client!"

这表明服务器成功接收了来自客户端的消息并回复了同样的消息