demowolf

QT tcp Socket 通信开发

折腾了很久TCP IP通信机制。

以前虽然看过bsd tcp/ip的so called 基础通信代码。什么bind, listen ,accept , receive, write, read，但是一直没真正理解。

这次由于公司需求，我狠狠地读了代码，并且搬出QT老本行，开始了QT For windows的编程。

这个大体构架是做一个聊天室软件。

每个client都可以给服务器TCP发消息，服务器通过TCP给各个客户端转发消息。

服务器端代码：

Server.cpp 继承 QTcpServer 主要用来listen to some port , 侦听到端口后，继承重写了incomingConnection函数，来new 如下的一个代码

tcpClientSocket.cpp 这个继承QTcpSocket ，用来 server.cpp里被 New 出来，接受各种请求

它重写了函数dataReceived , 即各种客户端发来的请求数据，（注意，这个不是第一步的connect状态，这个是业务逻辑上得请求，比如我给server发送了“你好” ）。

这一步处理好后，便开始给各个客户端分发同样的消息“你好” 。使用方法，很简单，QTcpSocket的write方法即可。

这里的细节重点是，在server.cpp里，每个new出来的TcpClientSocket的指针，我放到一个QLIST< TcpClientSocket * >模板里。这样，只要你不删去这个节点，这个TCP链接就一直存在，嘿嘿，神奇吧。

刚开始我看QT自带example ，fortuneclient and threaded fortune server；我试图着在example的基础上修改代码，一步步达到目的。结果发现他的业务逻辑，总是write后就自动disconnected，我以为不disconnected，就能长链接，结果总是出错。

我一直纳闷，这是为什么呢？我用了个List保存了socket的descriptor，以为留着套接字的描述符，就可以下次再调出来用用。实际呢，必须创建链路的时刻，就保存指针。TCP链接，指针在，链路在。指针亡，链路亡。

这也验证了我的想法，所谓一个真正的通信链路SOCKET的创建，是这样执行下去的。在APP层，我们调用了connect，实际OS对网卡发送了连接对方的信号，这个电子，一路走过去，直到accept , 这一个链路创建了，在网卡开辟了区域了，在系统OS也开辟了内存，两方都为此一直保持着这段数据的存在，指针即维系一个网络TCP链路的关键。

这就意味着，客户端无需写什么侦听代码来接受服务器端的消息，直接保持那个链路，消息自然就可以发过来，触发dataReceived信号。

写完代码后，我测试了一下，3个客户端同时链接TCP服务器端的5566端口，全部成功。

曾经很纠结我的所谓端口只能被一个占用。看来，理论远不如实际来的直接。

最后，我还是贴个代码吧。我知道，当一个人寻找各类消息的时候，代码总是最先看得，谁喜欢看人家博客唠叨半天，不讲大道理啊！

服务器端：

代码结构直接看插图

chatserver.h

*********************

#ifndef CHATSERVER_H

#define CHATSERVER_H

#include

#include "tcpclientsocket.h"

class ChatServer : public QTcpServer

{

Q_OBJECT

public:

ChatServer(QObject *parent = 0,int port=0);

void PushMessage();

QList tcpClientSocketList;

signals:

void updateServer(QString,int);

public slots:

void updateClients(QString,int);

void slotDisconnected(int);

protected:

void incomingConnection(int socketDescriptor);

private:

QStringList fortunes;

int onlineDescriptor;

};

#endif // CHATSERVER_H

*********************

chatserver.cpp

*********************

#include "chatserver.h"

#include "chatthread.h"

#include

ChatServer::ChatServer(QObject *parent,int port)

: QTcpServer(parent)

{

fortunes << tr("Searching for people...")

<< tr("You've find a people. Try say hello!")

<< tr("You've disconnected.");

listen(QHostAddress::Any,port);

}

void ChatServer::incomingConnection(int socketDescriptor)

{

TcpClientSocket *tcpClientSocket=new TcpClientSocket(this);

connect(tcpClientSocket,SIGNAL(updateClients(QString,int)),this,SLOT(updateClients(QString,int)));

connect(tcpClientSocket,SIGNAL(disconnect(int)),this,SLOT(slotDisconnected(int)));

tcpClientSocket->setSocketDescriptor(socketDescriptor);

tcpClientSocketList.append(tcpClientSocket);

onlineDescriptor=socketDescriptor;

QString fortune = fortunes.at(qrand() % fortunes.size());

// QString fortune = fortunes.at(0);

ChatThread *thread = new ChatThread(socketDescriptor, fortune, this);

connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));

thread->start();

}

void ChatServer::updateClients(QString msg, int length)

{

// emit updateServer(msg,length);

for(int i=0;i

{

QTcpSocket *item=tcpClientSocketList.at(i);

if(item->write(msg.toLatin1(),length)!=length)

{

continue;

}

void ChatServer::slotDisconnected(int descriptor)

{

for (int i=0;i

{

QTcpSocket *item=tcpClientSocketList.at(i);

if(item->socketDescriptor()==descriptor)

{

tcpClientSocketList.removeAt(i);

return;

}

return;

}

void ChatServer::PushMessage()

{

QString testString;

testString="fuck u";

updateClients(testString,testString.length());

ChatThread *thread = new ChatThread(onlineDescriptor, testString, this);

connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));

thread->start();

}

*********************

chatui.h

*********************

#ifndef CHATUI_H

#define CHATUI_H

#include

#include "chatserver.h"

QT_BEGIN_NAMESPACE

class QLabel;

class QPushButton;

QT_END_NAMESPACE

class ChatUi : public QDialog

{

Q_OBJECT

public:

ChatUi(QWidget *parent = 0);

private slots:

void Test();

private:

QLabel *statusLabel;

QPushButton *quitButton;

QPushButton *testButton;

ChatServer *server;

};

#endif // CHATUI_H

*********************

chatui.cpp

*********************

#include "chatui.h"

#include "chatserver.h"

#include

ChatUi::ChatUi(QWidget *parent)

:QDialog(parent)

{

statusLabel = new QLabel;

quitButton=new QPushButton(tr("Quit"));

quitButton->setAutoDefault(false);

testButton=new QPushButton(tr("Test"));

testButton->setAutoDefault(false);

server=new ChatServer(this,5566);

if (!server->isListening()) {

QMessageBox::critical(this, tr("Chat Server"),

tr("Unable to start the server: %1.")

.arg(server->errorString()));

close();

return;

}

QString ipAddress;

QList ipAddressesList = QNetworkInterface::allAddresses();

for (int i = 0; i < ipAddressesList.size(); ++i) {

if (ipAddressesList.at(i) != QHostAddress::LocalHost &&

ipAddressesList.at(i).toIPv4Address()) {

ipAddress = ipAddressesList.at(i).toString();

break;

}

if (ipAddress.isEmpty())

ipAddress = QHostAddress(QHostAddress::LocalHost).toString();

statusLabel->setText(tr("The server is running on/n/nIP: %1/nport: %2/n/n"

"Run the Fortune Client example now.")

.arg(ipAddress).arg(server->serverPort()));

connect(quitButton,SIGNAL(clicked()),this,SLOT(close()));

connect(testButton,SIGNAL(clicked()),this,SLOT(Test()));

QHBoxLayout *buttonLayout = new QHBoxLayout;

buttonLayout->addStretch(1);

buttonLayout->addWidget(quitButton);

buttonLayout->addStretch(1);

buttonLayout->addWidget(testButton);

buttonLayout->addStretch(1);

QVBoxLayout *mainLayout = new QVBoxLayout;

mainLayout->addWidget(statusLabel);

mainLayout->addLayout(buttonLayout);

setLayout(mainLayout);

setWindowTitle(tr("Chat Server"));

}

void ChatUi::Test()

{

server->PushMessage();

}

*********************

tcpclientsocket.h

*********************

#ifndef TCPCLIENTSOCKET_H

#define TCPCLIENTSOCKET_H

#include

class TcpClientSocket : public QTcpSocket

{

Q_OBJECT

public:

TcpClientSocket(QObject* parent=0);

~TcpClientSocket();

signals:

void updateClients(QString,int);

void disconnected(int);

protected slots:

void dataReceived();

// void slotDisconnected();

};

#endif // TCPCLIENTSOCKET_H

*********************

tcpclientsocket.cpp

*********************

#include "tcpclientsocket.h"

TcpClientSocket::TcpClientSocket(QObject* parent)

{

connect(this,SIGNAL(readyRead()),this,SLOT(dataReceived()));

connect(this,SIGNAL(disconnected()),this,SLOT(slotDisconnected()));

}

TcpClientSocket::~TcpClientSocket()

{

}

void TcpClientSocket::dataReceived()

{

while(bytesAvailable()>0)

{

char buf[1024];

int length=bytesAvailable();

read(buf,length);

QString msg=buf;

emit updateClients(msg,length);

}

*********************

下面是客户端代码

client.h

*********************

/****************************************************************************

** Contact: Nokia Corporation ([email protected])

** This file is part of the examples of the Qt Toolkit.

** $QT_BEGIN_LICENSE:LGPL$

** Commercial Usage

** Licensees holding valid Qt Commercial licenses may use this file in

** accordance with the Qt Commercial License Agreement provided with the

** Software or, alternatively, in accordance with the terms contained in

** a written agreement between you and Nokia.

** GNU Lesser General Public License Usage

** Alternatively, this file may be used under the terms of the GNU Lesser

** General Public License version 2.1 as published by the Free Software

** Foundation and appearing in the file LICENSE.LGPL included in the

** packaging of this file. Please review the following information to

** ensure the GNU Lesser General Public License version 2.1 requirements

** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.

** In addition, as a special exception, Nokia gives you certain additional

** rights. These rights are described in the Nokia Qt LGPL Exception

** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.

** GNU General Public License Usage

** Alternatively, this file may be used under the terms of the GNU

** General Public License version 3.0 as published by the Free Software

** Foundation and appearing in the file LICENSE.GPL included in the

** packaging of this file. Please review the following information to

** ensure the GNU General Public License version 3.0 requirements will be

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** If you have questions regarding the use of this file, please contact

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** $QT_END_LICENSE$

****************************************************************************/

#ifndef CLIENT_H

#define CLIENT_H

#include

QT_BEGIN_NAMESPACE

class QDialogButtonBox;

class QLabel;

class QLineEdit;

class QPushButton;

class QTcpSocket;

QT_END_NAMESPACE

//! [0]

class Client : public QDialog

{

Q_OBJECT

public:

Client(QWidget *parent = 0);

private slots:

void requestNewFortune();

void readFortune();

void displayError(QAbstractSocket::SocketError socketError);

void enableGetFortuneButton();

void slotConnected();

private:

QLabel *hostLabel;

QLabel *portLabel;

QLineEdit *hostLineEdit;

QLineEdit *portLineEdit;

QLabel *statusLabel;

QPushButton *getFortuneButton;

QPushButton *quitButton;

QDialogButtonBox *buttonBox;

QTcpSocket *tcpSocket;

QString currentFortune;

quint16 blockSize;

#ifdef Q_OS_SYMBIAN

bool isDefaultIapSet;

#endif

};

//! [0]

#endif

*********************

client.cpp