Qt网络编程之QTCPSocket和QTCPServer实例（二）

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 
#include 

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 
#include 
#include 
#include 
#include 

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 
#include 
#include 
#include 

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 
#include 

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 
#include 
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 
#include 

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。