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 <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_SYMBIANbool 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 toQString ipAddress;QList<QHostAddress> ipAddressesList = QNetworkInterface::allAddresses();// use the first non-localhost IPv4 addressfor (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 localhostif (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_SYMBIANisDefaultIapSet = false;#endif//! [5]}//! [5]//! [6]void Client::requestNewFortune(){getFortuneButton->setEnabled(false);#ifdef Q_OS_SYMBIANif(!isDefaultIapSet) {qt_SetDefaultIap();isDefaultIapSet = true;}#endifblockSize = 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;}

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

转自;http://blog.csdn.net/demowolf/article/details/5598879