Qt实现UDP通信的示例代码

设想有如下场景：若干的客户端与服务器端建立连接，建立连接后，服务器端随机发送字符串给客户端，客户端打印输出。该节案例使用TCP编程。

服务器端-单线程

头文件

#pragma once
//
//tcp服务端-单线程处理客户端连接
#include <QAbstractSocket>
#include <QObject>
 
class QTcpServer;
class SimpleTcpSocketServerDemo : public QObject
{ 
 
 Q_OBJECT
 
public:
 SimpleTcpSocketServerDemo();
 
private slots:
 void sendData();
 void displayError(QAbstractSocket::SocketError socketError);
 
private:
 QStringList m_oData;
 QTcpServer *m_pTcpServer;
};
 
void testSimpleTcpSocketServerDemo();

源文件

#include "SimpleTcpSocketServerDemo.h"
#include <assert.h>
#include <QTcpServer>
#include <QTcpSocket>
#include <QDebug>
#include <QDataStream>
SimpleTcpSocketServerDemo::SimpleTcpSocketServerDemo()
{ 
 
//初始换原始数据
m_oData << tr("You've been leading a dog's life. Stay off the furniture.")
<< tr("You've got to think about tomorrow.")
<< tr("You will be surprised by a loud noise.")
<< tr("You will feel hungry again in another hour.")
<< tr("You might have mail.")
<< tr("You cannot kill time without injuring eternity.")
<< tr("Computers are not intelligent. They only think they are.");
//1. 创建TCP对象
m_pTcpServer = new QTcpServer(this);
//2. 新连接、错误信号
connect(m_pTcpServer, &QTcpServer::newConnection, this, &SimpleTcpSocketServerDemo::sendData);
connect(m_pTcpServer, &QTcpServer::acceptError, this, &SimpleTcpSocketServerDemo::displayError);
//3. 启动服务端
if (!m_pTcpServer->listen(QHostAddress::Any, 8888))
{ 
 
qDebug() << "m_pTcpServer->listen() error";
assert(false);
}
}
void SimpleTcpSocketServerDemo::sendData()
{ 
 
//获取服务端数据
QString sWriteData = m_oData.at(qrand() % m_oData.size());
//获取与客户端通信的socket
QTcpSocket* pClientConnection = m_pTcpServer->nextPendingConnection();
//从客户端读数据
QString sReadData = pClientConnection->readAll();
qDebug() << "SimpleTcpSocketServerDemo::readDataFromClient " << pClientConnection;
//与客户端写数据
qDebug() << "SimpleTcpSocketServerDemo::writeDataToClient " << sWriteData;
pClientConnection->write(sWriteData.toUtf8());
// //与客户端断开连接
// connect(pClientConnection, &QTcpSocket::disconnected, this, &SimpleTcpSocketServerDemo::deleteLater);
// pClientConnection->disconnectFromHost();
}
void SimpleTcpSocketServerDemo::displayError(QAbstractSocket::SocketError socketError)
{ 
 
qDebug() << "SimpleTcpSocketServerDemo::displayError " << socketError;
}
void testSimpleTcpSocketServerDemo()
{ 
 
//这样写会内存泄漏，如此写方便测试。
SimpleTcpSocketServerDemo* pSimpleTcpSocketServer = new SimpleTcpSocketServerDemo;
}

客户端

头文件

#pragma once
//
//客户端
#include <QObject>
#include <QAbstractSocket>
#include <QRunnable>
#include <QThreadPool>
class QTcpSocket;
class SimpleTcpSocketClientDemo : public QObject
{ 
 
Q_OBJECT
public:
SimpleTcpSocketClientDemo();
private slots:
void connected();
void readyRead();
void error(QAbstractSocket::SocketError socketError);
private:
QTcpSocket* m_pTcpSocket;
};
class ClientRunnable : public QRunnable
{ 
 
public:
void run();
};
void testSimpleTcpSocketClientDemo();

源文件

#include "SimpleTcpSocketClientDemo.h"
#include <QTcpSocket>
#include <QDebug>
SimpleTcpSocketClientDemo::SimpleTcpSocketClientDemo()
{ 
 
//1. 创建TCP套接字对象
m_pTcpSocket = new QTcpSocket(this);
//2. 已连接、数据可读、失败信号连接
connect(m_pTcpSocket, &QTcpSocket::connected, this, &SimpleTcpSocketClientDemo::connected);
connect(m_pTcpSocket, &QIODevice::readyRead, this, &SimpleTcpSocketClientDemo::readyRead);
typedef void (QAbstractSocket::*QAbstractSocketErrorSignal)(QAbstractSocket::SocketError);
connect(m_pTcpSocket, static_cast<QAbstractSocketErrorSignal>(&QTcpSocket::error), this, &SimpleTcpSocketClientDemo::error);
//3. 与服务器端建立连接
m_pTcpSocket->connectToHost("127.0.0.1", 8888);
//4. 同步处理-等待数据可读
m_pTcpSocket->waitForReadyRead();
}
void SimpleTcpSocketClientDemo::readyRead()
{ 
 
qDebug() << "SimpleTcpSocketClientDemo::readyRead " << m_pTcpSocket->readAll();
}
void SimpleTcpSocketClientDemo::connected()
{ 
 
qDebug() << "SimpleTcpSocketClientDemo::connected successfully";
}
void SimpleTcpSocketClientDemo::error(QAbstractSocket::SocketError socketError)
{ 
 
qDebug() << "SimpleTcpSocketClientDemo::error " << socketError;
}
void ClientRunnable::run()
{ 
 
//这样写会内存泄漏，如此写方便测试。
SimpleTcpSocketClientDemo* pSimpleTcpSocketClient = new SimpleTcpSocketClientDemo;
}
#define CLINET_COUNT 2000 //客户端的数量
void testSimpleTcpSocketClientDemo()
{ 
 
QTime oTime;
oTime.start();
//同步线程池的方式模拟多个客户端与服务器端交互
for (int nIndex = 0; nIndex < CLINET_COUNT; ++nIndex)
{ 
 
ClientRunnable* pRunnable = new ClientRunnable;
pRunnable->setAutoDelete(false);
QThreadPool::globalInstance()->start(pRunnable);
}
QThreadPool::globalInstance()->waitForDone(30 * 1000);
qDebug() << "connect count: " << CLINET_COUNT << "total time: " << (double)oTime.elapsed() / double(1000) << "s";
}

测试结果-单线程

服务器端

SimpleTcpSocketServerDemo::readDataFromClient  QTcpSocket(0x2f27f308)
SimpleTcpSocketServerDemo::writeDataToClient  "You will feel hungry again in another hour."
SimpleTcpSocketServerDemo::readDataFromClient  QTcpSocket(0x2eb61cf0)
SimpleTcpSocketServerDemo::writeDataToClient  "You might have mail."
.........

客户端

SimpleTcpSocketClientDemo::connected  successfully
SimpleTcpSocketClientDemo::readyRead  "You might have mail."
SimpleTcpSocketClientDemo::connected  successfully
SimpleTcpSocketClientDemo::readyRead  "You will feel hungry again in another hour."
.........
connect count:  2000 total time:  3.926 s

通过测试输出，可以看到服务器端与客户端建立了正确的连接并且数据交换。

– 实际测试数据：2000个连接，耗时4s左右，CPU使用率10%左右。

通过阅读服务器端，发现单线程处理客户端的连接效率较低。服务器端可修改为多线程处理客户端连接，代码如下：

服务器端-多线程

头文件

#pragma once
//
//服务器端-多线程处理客户端连接
#include <QTcpServer>
#include <QThread>
class MultiThreadTcpSocketServerDemo : public QTcpServer
{ 
 
public:
MultiThreadTcpSocketServerDemo();
//This virtual function is called by QTcpServer when a new connection is available. 
//The socketDescriptor argument is the native socket descriptor for the accepted connection.
virtual void incomingConnection(qintptr handle);
private:
QStringList m_oData;
};
//处理线程
class ServerHandleThread : public QThread
{ 
 
Q_OBJECT
public:
ServerHandleThread(qintptr handle, const QString& sWriteData);
virtual void run();
private:
qintptr m_nHandle;
QString m_sWriteData;
};
void testMultiThreadTcpSocketServerDemo();

//This virtual function is called by QTcpServer when a new connection is available. //The socketDescriptor argument is the native socket descriptor for the accepted connection. virtual void incomingConnection(qintptr handle); //该虚函数是重点

源文件

#include "MultiThreadTcpSocketServerDemo.h"
#include <QDebug>
#include <QTcpSocket>
MultiThreadTcpSocketServerDemo::MultiThreadTcpSocketServerDemo()
{ 
 
//初始换原始数据
m_oData << tr("You've been leading a dog's life. Stay off the furniture.")
<< tr("You've got to think about tomorrow.")
<< tr("You will be surprised by a loud noise.")
<< tr("You will feel hungry again in another hour.")
<< tr("You might have mail.")
<< tr("You cannot kill time without injuring eternity.")
<< tr("Computers are not intelligent. They only think they are.");
}
void MultiThreadTcpSocketServerDemo::incomingConnection(qintptr handle)
{ 
 
//获取服务端数据
QString sWriteData = m_oData.at(qrand() % m_oData.size());
qDebug() << "MultiThreadTcpSocketServerDemo::incomingConnection" << handle;
ServerHandleThread* pThread = new ServerHandleThread(handle, sWriteData);
connect(pThread, &ServerHandleThread::finished, pThread, &ServerHandleThread::deleteLater);
pThread->start();
}
ServerHandleThread::ServerHandleThread(qintptr handle, const QString& sWriteData)
:m_sWriteData(sWriteData), m_nHandle(handle)
{ 
 
}
void ServerHandleThread::run()
{ 
 
//1. 建立与客户端通信的TCP套接字
QTcpSocket oTcpSocket;
if (!oTcpSocket.setSocketDescriptor(m_nHandle))
{ 
 
qDebug() << "oTcpSocket.setSocketDescriptor error";
return;
}
//2. 向客户端写数据
qDebug() << "MultiThreadTcpSocketServerDemo::readDataFromClient" << &oTcpSocket;
qDebug() << "MultiThreadTcpSocketServerDemo::writeDataToClient" << m_sWriteData;
oTcpSocket.write(m_sWriteData.toUtf8());
oTcpSocket.disconnectFromHost();
oTcpSocket.waitForDisconnected();
}
void testMultiThreadTcpSocketServerDemo()
{ 
 
//1. 建立服务器端套接字
MultiThreadTcpSocketServerDemo* m_pTcpServer = new MultiThreadTcpSocketServerDemo();
//2. 启动服务端
if (!m_pTcpServer->listen(QHostAddress::Any, 8888))
{ 
 
qDebug() << "m_pTcpServer->listen() error";
}
}

测试结果-多线程

客户端

SimpleTcpSocketClientDemo::connected  successfully
SimpleTcpSocketClientDemo::readyRead  "You might have mail."
SimpleTcpSocketClientDemo::connected  successfully
SimpleTcpSocketClientDemo::readyRead  "You will feel hungry again in another hour."
.........
connect count:  2000 total time:  6.403 s

– 实际测试数据：2000个连接，耗时6.5s左右，CPU使用率20%左右。

可见服务器端采用多线程可充分利用CPU，但是频繁的切换线程也会性能下降（耗时）。

通过本案例的代码实现可以了解TCP服务器端/客户端编程的基本思路。并且验证了服务器端单线程和多线程的效率对比。 在windows中，可通过IOCP提高服务期端的效率，后面会详细讲解。