QT tcp Socket 通信开发

 

转自：http://blog.csdn.net/demowolf/archive/2010/05/17/5598879.aspx

 

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：

chatserver.h*********************#ifndef CHATSERVER_H#define CHATSERVER_H#include <QTcpServer>#include <QStringList>#include "tcpclientsocket.h"class ChatServer : public QTcpServer{ Q_OBJECTpublic: ChatServer(QObject *parent = 0,int port=0); void PushMessage(); QList<TcpClientSocket*> 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 <stdlib.h>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<tcpClientSocketList.count();i++) { QTcpSocket *item=tcpClientSocketList.at(i); if(item->write(msg.toLatin1(),length)!=length) { continue; } }}void ChatServer::slotDisconnected(int descriptor){ for (int i=0;i<tcpClientSocketList.count();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 <QDialog>#include "chatserver.h"QT_BEGIN_NAMESPACEclass QLabel;class QPushButton;QT_END_NAMESPACEclass ChatUi : public QDialog{ Q_OBJECTpublic: 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 <QtGui>#include <QtNetwork>#include <stdlib.h>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<QHostAddress> 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 <QTcpSocket>class TcpClientSocket : public QTcpSocket{ Q_OBJECTpublic: 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*********************#ifndef CLIENT_H#define CLIENT_H#include <QDialog>#include <QTcpSocket>QT_BEGIN_NAMESPACEclass QDialogButtonBox;class QLabel;class QLineEdit;class QPushButton;class QTcpSocket;QT_END_NAMESPACE//! [0]class Client : public QDialog{ Q_OBJECTpublic: 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*********************#include <QtGui>#include <QtNetwork>#include "client.h"#ifdef Q_OS_SYMBIAN#include "sym_iap_util.h"#endif//! [0]Client::Client(QWidget *parent) : QDialog(parent){//! [0] hostLabel = new QLabel(tr("&Server name:")); portLabel = new QLabel(tr("S&erver port:")); // find out which IP to connect to QString ipAddress; QList<QHostAddress> ipAddressesList = QNetworkInterface::allAddresses(); // use the first non-localhost IPv4 address 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 we did not find one, use IPv4 localhost if (ipAddress.isEmpty()) ipAddress = QHostAddress(QHostAddress::LocalHost).toString(); hostLineEdit = new QLineEdit(ipAddress); portLineEdit = new QLineEdit; portLineEdit->setValidator(new QIntValidator(1, 65535, this)); hostLabel->setBuddy(hostLineEdit); portLabel->setBuddy(portLineEdit); statusLabel = new QLabel(tr("This examples requires that you run the " "Fortune Server example as well.")); getFortuneButton = new QPushButton(tr("Get Fortune")); getFortuneButton->setDefault(true); getFortuneButton->setEnabled(false); quitButton = new QPushButton(tr("Quit")); buttonBox = new QDialogButtonBox; buttonBox->addButton(getFortuneButton, QDialogButtonBox::ActionRole); buttonBox->addButton(quitButton, QDialogButtonBox::RejectRole);//! [1] tcpSocket = new QTcpSocket(this);//! [1] connect(hostLineEdit, SIGNAL(textChanged(QString)), this, SLOT(enableGetFortuneButton())); connect(portLineEdit, SIGNAL(textChanged(QString)), this, SLOT(enableGetFortuneButton())); connect(getFortuneButton, SIGNAL(clicked()), this, SLOT(requestNewFortune())); connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));//! [2] //! [3] connect(tcpSocket,SIGNAL(connected()),this,SLOT(slotConnected())); connect(tcpSocket, SIGNAL(readyRead()), this, SLOT(readFortune()));//! [2] //! [4] connect(tcpSocket, SIGNAL(error(QAbstractSocket::SocketError)),//! [3] this, SLOT(displayError(QAbstractSocket::SocketError)));//! [4] QGridLayout *mainLayout = new QGridLayout; mainLayout->addWidget(hostLabel, 0, 0); mainLayout->addWidget(hostLineEdit, 0, 1); mainLayout->addWidget(portLabel, 1, 0); mainLayout->addWidget(portLineEdit, 1, 1); mainLayout->addWidget(statusLabel, 2, 0, 1, 2); mainLayout->addWidget(buttonBox, 3, 0, 1, 2); setLayout(mainLayout); setWindowTitle(tr("Fortune Client")); portLineEdit->setFocus();#ifdef Q_OS_SYMBIAN isDefaultIapSet = false;#endif//! [5]}//! [5]//! [6]void Client::requestNewFortune(){ getFortuneButton->setEnabled(false);#ifdef Q_OS_SYMBIAN if(!isDefaultIapSet) { qt_SetDefaultIap(); isDefaultIapSet = true; }#endif blockSize = 0; tcpSocket->abort();//! [7] tcpSocket->connectToHost(hostLineEdit->text(), portLineEdit->text().toInt());//! [7]}//! [6]//! [8]void Client::readFortune(){ while(tcpSocket->bytesAvailable()>0) { QByteArray datagram; datagram.resize(tcpSocket->bytesAvailable()); tcpSocket->read(datagram.data(),datagram.size()); QString msg=datagram.data(); statusLabel->setText(msg); getFortuneButton->setEnabled(true); } /*//! [9] QDataStream in(tcpSocket); in.setVersion(QDataStream::Qt_4_0); if (blockSize == 0) { if (tcpSocket->bytesAvailable() < (int)sizeof(quint16)) return; in >> blockSize; } if (tcpSocket->bytesAvailable() < blockSize) return; QString nextFortune; in >> nextFortune;//! [12] currentFortune = nextFortune;//! [9] statusLabel->setText(currentFortune); getFortuneButton->setEnabled(true);*/}//! [12]//! [13]void Client::displayError(QAbstractSocket::SocketError socketError){ switch (socketError) { case QAbstractSocket::RemoteHostClosedError: QMessageBox::information(this, tr("Fortune Client"), tr("Romote server closed illegally.")); break; case QAbstractSocket::HostNotFoundError: QMessageBox::information(this, tr("Fortune Client"), tr("The host was not found. Please check the " "host name and port settings.")); break; case QAbstractSocket::ConnectionRefusedError: QMessageBox::information(this, tr("Fortune Client"), tr("The connection was refused by the peer. " "Make sure the fortune server is running, " "and check that the host name and port " "settings are correct.")); break; default: QMessageBox::information(this, tr("Fortune Client"), tr("The following error occurred: %1.") .arg(tcpSocket->errorString())); } getFortuneButton->setEnabled(true);}//! [13]void Client::enableGetFortuneButton(){ getFortuneButton->setEnabled(!hostLineEdit->text().isEmpty() && !portLineEdit->text().isEmpty());}void Client::slotConnected(){ QString msg="hello,server"; tcpSocket->write(msg.toLatin1(),msg.length()); return;}*********************