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37.Qt网络与通信

1　　获取本机网络与通信

　　在网络应用中,经常需要获得本机的主机名.IP地址和硬件地址等网络信息.运用QHostInfo,QNetWorkInterface,QNetworkAddressEntry可获得本机的网络信息.

widget.h

 1 #ifndef WIDGET_H
 2 #define WIDGET_H
 3 
 4 #include <QWidget>
 5 #include <QLabel>
 6 #include <QPushButton>
 7 #include <QLineEdit>
 8 #include <QGridLayout>
 9 #include <QMessageBox>
10 
11 #include <QHostInfo>
12 #include <QNetworkInterface>
13 
14 
15 namespace Ui {
16 class Widget;
17 }
18 
19 class Widget : public QWidget
20 {
21     Q_OBJECT
22 
23 public:
24     explicit Widget(QWidget *parent = 0);
25     ~Widget();
26 
27  private:
28     QLabel *hostLabel;
29     QLineEdit *LineEditLocalHostName;
30     QLabel *ipLabel;
31     QLineEdit *LineEditAddress;
32 
33     QPushButton *detailBtn;
34 
35     QGridLayout *mainLayout;
36 
37 private:
38     Ui::Widget *ui;
39 
40 public:
41     void getHostInformation();
42 
43 public slots:
44     void slotDetail();
45 };
46 
47 #endif // WIDGET_H

widget.cpp

 1 #include "widget.h"
 2 #include "ui_widget.h"
 3 
 4 Widget::Widget(QWidget *parent) :
 5     QWidget(parent),
 6     ui(new Ui::Widget)
 7 {
 8     ui->setupUi(this);
 9     hostLabel = new QLabel(tr("主机名: "));
10     LineEditLocalHostName = new QLineEdit;
11     ipLabel = new QLabel(tr("IP 地址:"));
12     LineEditAddress = new QLineEdit;
13 
14     detailBtn = new QPushButton(tr("详细"));
15 
16     mainLayout = new QGridLayout(this);
17     mainLayout->addWidget(hostLabel,0,0);
18     mainLayout->addWidget(LineEditLocalHostName,0,1);
19     mainLayout->addWidget(ipLabel,1,0);
20     mainLayout->addWidget(LineEditAddress,1,1);
21     //第二行第0个,占两列
22     mainLayout->addWidget(detailBtn,2,0,1,2);
23 
24     getHostInformation();
25     connect(detailBtn,SIGNAL(clicked(bool)),this,SLOT(slotDetail()));
26 }
27 
28 Widget::~Widget()
29 {
30     delete ui;
31 }
32 
33 void Widget::getHostInformation()
34 {
35     //获得本机主机名.QHostInfo提供了一系列有关网络信息的静态函数,
36     //可以根据主机名获得分配的IP地址,也可以根据IP地址获得相应的主机名
37     QString localHostName = QHostInfo::localHostName();
38     LineEditLocalHostName->setText(localHostName);
39 
40     //根据主机名获得相关主机信息,包括IP地址等.
41     //QHostInfo::fromName()函数通过主机名查找IP地址信息
42     QHostInfo hostInfo = QHostInfo::fromName(localHostName);
43 
44     //获得主机的IP地址列表
45     QList<QHostAddress> listAddress = hostInfo.addresses();
46 
47     //在不为空的情况下,使用第一个IP地址
48     if(!listAddress.isEmpty())
49     {
50         LineEditAddress->setText(listAddress.first().toString());
51     }
52 }
53 
54 void Widget::slotDetail()
55 {
56     QString detail="";
57     //QNetworkInterface类提供了一个IP地址和网络接口的列表
58     QList<QNetworkInterface> list=QNetworkInterface::allInterfaces();
59 
60     for(int i=0;i<list.count();i++)
61     {
62         QNetworkInterface interface=list.at(i);
63 
64         //获得网络接口的名称
65         detail=detail+tr("设备: ")+interface.name()+"
";
66         //获得网络接口的名称
67         detail=detail+tr("硬件地址:")+interface.hardwareAddress()+"
";
68 
69         //每个网络接口包括0个或多个IP地址,
70         //每个IP地址有选择性地与一个子网掩码和一个广播地址相关联
71         //QNetworkAddressEntry类存储了被网络接口支持的一个IP地址,
72         //同时还包括与之相关的子网掩码和广播地址
73         QList<QNetworkAddressEntry> entryList=interface.addressEntries();
74 
75 
76         for(int j=0;j<entryList.count();j++)
77         {
78             QNetworkAddressEntry entry = entryList.at(j);
79             detail=detail+"	"+tr("IP地址: ")+entry.ip().toString()+"
";
80             detail=detail+"	"+tr("子网掩码: ")+entry.netmask().toString()+"
";
81             detail=detail+"	"+tr("广播地址: ")+entry.broadcast().toString()+"
";
82         }
83         QMessageBox::information(this,tr("Detail"),detail);
84     }
85 }

main.cpp

 1 #include "widget.h"
 2 #include <QApplication>
 3 
 4 int main(int argc, char *argv[])
 5 {
 6     QApplication a(argc, argv);
 7     Widget w;
 8     w.show();
 9 
10     return a.exec();
11 }

2　　基于UDP的网络广播程序

　　2.1　　UDP(user data protocol)是一种简单轻量级,不可靠,面向数据报无连接的传输协议,可以用在不是十分重要的场合

　　2.2　　UDP编程模型

　　在UDP方式下客户端并不与服务器建立连接,它只负责调用发送函数向服务器法术数据报.类似的服务器不从客户端接收连接,只负责调用接收函数,等待来自某客户端的数据到达.Qt中通过QUdpSocket类实现UDP协议的编程.

服务器端:

udpserver.h

 1 #ifndef UDPSERVER_H
 2 #define UDPSERVER_H
 3 
 4 #include <QDialog>
 5 #include <QLabel>
 6 #include <QPushButton>
 7 #include <QVBoxLayout>
 8 #include <QLineEdit>
 9 #include <QUdpSocket>
10 #include <QTimer>
11 
12 namespace Ui {
13 class UdpServer;
14 }
15 
16 class UdpServer : public QDialog
17 {
18     Q_OBJECT
19 
20 public:
21     explicit UdpServer(QWidget *parent = 0,Qt::WindowFlags f=0);
22     ~UdpServer();
23 
24 public slots:
25     void StartBtnClicked();
26     void timeout();
27 
28 private:
29     int port;
30     bool isStarted;
31     QUdpSocket *udpSocket;
32     QTimer *timer;
33 
34 private:
35     QLabel *TimerLabel;
36     QLineEdit *TextLineEdit;
37     QPushButton *StartBtn;
38     QVBoxLayout *mainLayout;
39 
40 private:
41     Ui::UdpServer *ui;
42 
43 
44 };
45 
46 #endif // UDPSERVER_H

udpserver.cpp

 1 #include "udpserver.h"
 2 #include "ui_udpserver.h"
 3 
 4 #include <QHostAddress>
 5 
 6 UdpServer::UdpServer(QWidget *parent,Qt::WindowFlags f) :
 7     QDialog(parent,f),
 8     ui(new Ui::UdpServer)
 9 {
10     ui->setupUi(this);
11 
12     setWindowTitle(tr("UDP 服务器"));
13 
14     TimerLabel = new QLabel(tr("计时器:"),this);
15     TextLineEdit = new QLineEdit(this);
16     StartBtn = new QPushButton(tr("开始"),this);
17 
18     //设置垂直布局
19     mainLayout = new QVBoxLayout(this);
20     mainLayout->addWidget(TimerLabel);
21     mainLayout->addWidget(TextLineEdit);
22     mainLayout->addWidget(StartBtn);
23 
24     connect(StartBtn,SIGNAL(clicked(bool)),this,SLOT(StartBtnClicked()));
25 
26     //设置UDP的端口号参数,服务器定时向此端口发送广播消息
27     port = 5555;
28     isStarted = false;
29     udpSocket = new QUdpSocket(this);
30     //创建定时器
31     timer = new QTimer(this);
32     //定时发送广播消息
33     connect(timer,SIGNAL(timeout()),this,SLOT(timeout()));
34 }
35 
36 UdpServer::~UdpServer()
37 {
38     delete ui;
39 }
40 
41 void UdpServer::StartBtnClicked()
42 {
43     //打开
44     if(!isStarted)
45     {
46         StartBtn->setText(tr("停止"));
47         //每隔1000秒发送一个消息
48         timer->start(1000);
49         isStarted=true;
50     }
51     else
52     {
53         StartBtn->setText(tr("开始"));
54         isStarted = false;
55         timer->stop();
56     }
57 }
58 
59 void UdpServer::timeout()
60 {
61     QString msg = TextLineEdit->text();
62     int length=0;
63     if(msg=="")
64     {
65         return;
66     }
67 
68     //QHostAddress::Broadcast 指定向广播地址发送
69     if(length=udpSocket->writeDatagram(msg.toLatin1(),
70                msg.length(),QHostAddress::Broadcast,port)!=msg.length())
71     {
72         return;
73     }
74 }

udpclient.h

 1 #ifndef UDPCLIENT_H
 2 #define UDPCLIENT_H
 3 
 4 #include <QDialog>
 5 #include <QVBoxLayout>
 6 #include <QTextEdit>
 7 #include <QPushButton>
 8 #include <QUdpSocket>
 9 
10 namespace Ui {
11 class UdpClient;
12 }
13 
14 class UdpClient : public QDialog
15 {
16     Q_OBJECT
17 
18 public:
19     explicit UdpClient(QWidget *parent = 0);
20     ~UdpClient();
21 
22 public slots:
23     void CloseBtnClicked();
24     void dataReceived();
25 
26 private:
27     int port;
28     QUdpSocket *udpSocket;
29 
30 private:
31     Ui::UdpClient *ui;
32     QTextEdit *ReceiveTextEdit;
33     QPushButton *closeBtn;
34     QVBoxLayout *mainLayout;
35 };
36 
37 #endif // UDPCLIENT_H

udpclient.cpp

 1 #include "udpclient.h"
 2 #include "ui_udpclient.h"
 3 #include <QMessageBox>
 4 #include <QHostAddress>
 5 
 6 UdpClient::UdpClient(QWidget *parent) :
 7     QDialog(parent),
 8     ui(new Ui::UdpClient)
 9 {
10     ui->setupUi(this);
11 
12     setWindowTitle(tr("UDP 客户端"));
13 
14     ReceiveTextEdit = new QTextEdit(this);
15 
16     closeBtn = new QPushButton(tr("关闭"),this);
17 
18     mainLayout = new QVBoxLayout(this);
19     mainLayout->addWidget(ReceiveTextEdit);
20     mainLayout->addWidget(closeBtn);
21 
22     connect(closeBtn,SIGNAL(clicked(bool)),this,SLOT(CloseBtnClicked()));
23 
24     //设置UDP的端口号参数,指定在此端口上监听数据
25     port = 5555;
26 
27     //创建一个QUdpSocket
28     udpSocket = new QUdpSocket(this);
29     //连接QIODevice的readyRead()信号
30     //QUdpSocket也是一个I/O设备,从QIODevice继承而来,当有数据到达I/O设备时,发出readyRead()信号
31     connect(udpSocket,SIGNAL(readyRead()),this,SLOT(dataReceived()));
32 
33     //绑定到指定的端口上
34     bool result=udpSocket->bind(port);
35 
36     if(!result)
37     {
38         QMessageBox::information(this,tr("error"),tr("udp socket create error!"));
39         return;
40     }
41 }
42 
43 UdpClient::~UdpClient()
44 {
45     delete ui;
46 }
47 
48 void UdpClient::CloseBtnClicked()
49 {
50     close();
51 }
52 
53 void UdpClient::dataReceived()
54 {
55     //判断UdpSocket中是否有数据报可读
56     //hasPendingDatagrams()方法在至少有一个数据报可读时返回true
57     while(udpSocket->hasPendingDatagrams())
58     {
59         //实现读取第一个数据报
60         //pendingDataSize()可以获得第一个数据报的长度
61         QByteArray datagram;
62         datagram.resize(udpSocket->pendingDatagramSize());
63         udpSocket->readDatagram(datagram.data(),datagram.size());
64 
65         QString msg = datagram.data();
66         //显示数据内容
67         ReceiveTextEdit->insertPlainText(msg);
68     }
69 }

3　　基于TCP的网络聊天室程序

　　TCP协议能为应用程序提供可靠的通信连接,使一台计算机发出的字节流无差错地送达网络上的其他计算机.因此,对可靠性要求高的数据通信系统往往使用TCP协议传输数据,但在正则收发数据前通信双方必须首先建立连接.

　　首先启动服务器,一段时间后启动客户端,它与此服务器经过三次握手后建立连接.此后的一段时间内,客户端向服务器发送一个请求,服务器处理这个请求,并为客户端发回一个响应.这个过程一直持续下去,知道客户端为服务器发一个文件结束符,并关闭客户端连接,接着服务器也关闭服务器的连接,结束运行或等待一个新的客户端连接.

　　Qt中通过QTcpSocket类实现TCP协议的编程.

代码示例:

服务器端

tcpserver.h

 1 #ifndef TCPSERVER_H
 2 #define TCPSERVER_H
 3 
 4 #include <QDialog>
 5 #include <QListWidget>
 6 #include <QLabel>
 7 #include <QLineEdit>
 8 #include <QPushButton>
 9 #include <QGridLayout>
10 #include "serverh.h"
11 
12 namespace Ui {
13 class TcpServer;
14 }
15 
16 class TcpServer : public QDialog
17 {
18     Q_OBJECT
19 
20 public:
21     explicit TcpServer(QWidget *parent = 0);
22     ~TcpServer();
23 
24 private:
25     Ui::TcpServer *ui;
26     QListWidget *ContentListWidget;
27     QLabel *PortLabe;
28     QLineEdit *PortLineEdit;
29     QPushButton *CreateBtn;
30     QGridLayout *mainLayout;
31 
32 private:
33     int port;
34     serverh *server;
35 
36 public slots:
37     void slotCreateServer();
38     void updateServer(QString,int);
39 
40 };
41 
42 #endif // TCPSERVER_H

tcpserver.cpp

 1 #include "tcpserver.h"
 2 #include "ui_tcpserver.h"
 3 
 4 TcpServer::TcpServer(QWidget *parent) :
 5     QDialog(parent),
 6     ui(new Ui::TcpServer)
 7 {
 8     ui->setupUi(this);
 9 
10     setWindowTitle(tr("TCP Server"));
11 
12     ContentListWidget = new QListWidget;
13 
14     PortLabe = new QLabel(tr("端口: "));
15     PortLineEdit = new QLineEdit();
16 
17     CreateBtn = new QPushButton(tr("创建聊天室"));
18 
19     mainLayout=new QGridLayout(this);
20     mainLayout->addWidget(ContentListWidget,0,0,1,2);
21     mainLayout->addWidget(PortLabe,1,0);
22     mainLayout->addWidget(PortLineEdit,1,1);
23     mainLayout->addWidget(CreateBtn,2,0,1,2);
24 
25     port=8010;
26     PortLineEdit->setText(QString::number(port));
27 
28     connect(CreateBtn,SIGNAL(clicked(bool)),this,SLOT(slotCreateServer()));
29 }
30 
31 TcpServer::~TcpServer()
32 {
33     delete ui;
34 }
35 
36 void TcpServer::slotCreateServer()
37 {
38     //创建一个serverh对象
39     server = new serverh(this,port);
40     //将serverh对象的updateServer()信号与相应的槽函数进行连接
41     connect(server,SIGNAL(updateServer(QString,int)),this,SLOT(updateServer(QString,int)));
42 
43     CreateBtn->setEnabled(false);
44 }
45 
46 void TcpServer::updateServer(QString msg , int length)
47 {
48     ContentListWidget->addItem(msg.left(length));
49 }

server.h

 1 #ifndef SERVERH_H
 2 #define SERVERH_H
 3 
 4 #include <QTcpServer>
 5 #include <QObject>
 6 
 7 #include "tcpclientsocket.h"//包含TCP的套接字
 8 
 9 class serverh : public QTcpServer
10 {
11     Q_OBJECT
12 public:
13     serverh(QObject *parent=0,int port=0);
14     //用来保存与每一个客户端连接的TcpClientSocket
15     QList<tcpclientsocket*> tcpClientSocketList;
16 
17 signals:
18     void updateServer(QString,int);
19 
20 public slots:
21     void updateClients(QString,int);
22     void slotDisconnected(int);
23 
24 protected:
25     void incomingConnection(int socketDescriptor);
26 };
27 
28 #endif // SERVERH_H

server.cpp

 1 #include "serverh.h"
 2 
 3 serverh::serverh(QObject *parent,int port):QTcpServer(parent)
 4 {
 5     //在指定的端口对任意地址进行监听
 6     //QHostAddress定义了几种特殊的IP地址
 7     //QHostAddress定义了几种特殊的IP地址,QHostAddress::Null表示一个空的地址
 8     //QHostAddress::LocalHost表示IPV4的本机地址127.0.0.1
 9     //QHostAddress::LocalHostIPV6表示IPv6的本机地址
10     //QHostAddress::Broadcast表示广播地址255.255.255.255
11     //QHostAddress::Any表示Ipv4的任意地址0.0.0.0
12     //QHostAddress::AnyIPv6表示IPv6的任意地址
13     listen(QHostAddress::Any,port);
14 }
15 
16 //当出现一个新的连接时,QTcpServer触发incomingConnection()函数,参数
17 //socketDescriptor指定连接的Socket描述符
18 void serverh::incomingConnection(int socketDescriptor)
19 {
20     qDebug() << "receive connect" << endl;
21     //创建一个新的TcpClientSocket客户端通信
22     tcpclientsocket  *tcpClientSocket = new tcpclientsocket(this);
23     //连接TcpClientSocket的updateClients信号
24     connect(tcpClientSocket,SIGNAL(updateClients(QString,int)),this,
25             SLOT(updateClients(QString,int)));
26     //连接TcpClientSocket的disconnect信号
27     connect(tcpClientSocket,SIGNAL(disconnected(int)),this,
28             SLOT(slotDisconnected(int)));
29 
30     //将tcpClient加入客户端套接字列表以便管理
31     tcpClientSocket->setSocketDescriptor(socketDescriptor);
32 
33     tcpClientSocketList.append(tcpClientSocket);
34 }
35 
36 void serverh::updateClients(QString msg, int length)
37 {
38     //发出updateServer信号,来通知服务器对话框更新相应的显示状态
39     qDebug() << msg << endl;
40     emit updateServer(msg,length);
41     qDebug() << msg << endl;
42     for(int i=0;i<tcpClientSocketList.count();i++)
43     {
44         QTcpSocket *item = tcpClientSocketList.at(i);
45         if(item->write(msg.toLatin1(),length)!=length)
46         {
47             continue;
48         }
49     }
50 }
51 
52 void serverh::slotDisconnected(int descriptor)
53 {
54     for(int i=0;i<tcpClientSocketList.count();i++)
55     {
56         QTcpSocket *item = tcpClientSocketList.at(i);
57 
58         if(item->socketDescriptor()==descriptor)
59         {
60             tcpClientSocketList.removeAt(i);
61             return;
62         }
63     }
64     return;
65 }

tcpclientsocket.h

 1 #ifndef TCPCLIENTSOCKET_H
 2 #define TCPCLIENTSOCKET_H
 3 
 4 #include <QTcpSocket>
 5 #include <QObject>
 6 
 7 class tcpclientsocket : public QTcpSocket
 8 {
 9     Q_OBJECT        //添加宏是为了实现信号和槽的通信
10 public:
11     tcpclientsocket(QObject *parent=0);
12 
13 signals:
14     void updateClients(QString ,int);
15     void disconnected(int);
16 
17 protected slots:
18     void dataReceived();
19     void slotDisconnected();
20 };
21 
22 #endif // TCPCLIENTSOCKET_H

tcpclientsocket.cpp

 1 #include "tcpclientsocket.h"
 2 #include <QDebug>
 3 
 4 tcpclientsocket::tcpclientsocket(QObject *parent)
 5 {
 6     //指定信号与槽的连接关系
 7     //readyRead()是QIODevice的signal,由QTcpSocket继承而来.QIODevice
 8     //是所有输入/输出设备的一个抽象类,其中定义了基本的接口,在Qt中,QTcpSocket也被
 9     //看做一个QIODevice,readyRead()信号在有数据到来时发出
10     connect(this,SIGNAL(readyRead()),this,SLOT(dataReceived()));
11     //信号在断开连接时发出
12     connect(this,SIGNAL(disconnected()),this,SLOT(slotDisconnected()));
13 }
14 
15 //当有数据到来的时候触发dataReceived()函数,从套接字中将有效数据取出,然后
16 //发出updateClients()信号.
17 //updateClients()信号是通知服务器向聊天室内的所有成员广播信息
18 void tcpclientsocket::dataReceived()
19 {
20     qDebug() << "accept message" << endl;
21     while(bytesAvailable()>0)
22     {
23         int length = bytesAvailable();
24         char buf[1024];
25         read(buf,length);
26 
27         qDebug() << buf << endl;
28         QString msg=buf;
29         qDebug() << msg << endl;
30         emit updateClients(msg,length);
31     }
32 }
33 
34 //槽函数slotDisconnected
35 void tcpclientsocket::slotDisconnected()
36 {
37     emit disconnected(this->socketDescriptor());
38 }

客户端

tcpclient.h

 1 #ifndef TCPCLIENT_H
 2 #define TCPCLIENT_H
 3 
 4 #include <QDialog>
 5 
 6 namespace Ui {
 7 class TcpClient;
 8 }
 9 
10 #include <QDialog>
11 #include <QListWidget>
12 #include <QLineEdit>
13 #include <QPushButton>
14 #include <QLabel>
15 #include <QGridLayout>
16 
17 #include <QHostAddress>
18 #include <QTcpSocket>
19 
20 class TcpClient : public QDialog
21 {
22     Q_OBJECT
23 
24 public:
25     explicit TcpClient(QWidget *parent = 0);
26     ~TcpClient();
27 
28 private:
29     Ui::TcpClient *ui;
30     QListWidget *contentListWidget;
31     QLineEdit *sendLineEdit;
32     QPushButton *sendBtn;
33     QLabel *userNameLabel;
34     QLineEdit *userNameLineEdit;
35     QLabel *serverIPLabel;
36     QLineEdit *serverIPLineEdit;
37     QLabel *portLabel;
38     QLineEdit *portLineEdit;
39     QPushButton *enterBtn;
40     QGridLayout *mainLayout;
41 
42 private:
43     bool status;
44     int port;
45     QHostAddress *serverIP;
46     QString userName;
47     QTcpSocket *tcpSocket;
48 
49 private slots:
50     void slotEnter();
51     void slotConnected();
52     void slotDisconnected();
53     void dataReceived();
54     void slotSend();
55 
56 
57 };
58 
59 #endif // TCPCLIENT_H

tcpclient.cpp

  1 #include "tcpclient.h"
  2 #include "ui_tcpclient.h"
  3 
  4 #include <QMessageBox>
  5 #include <QHostInfo>
  6 
  7 TcpClient::TcpClient(QWidget *parent) :
  8     QDialog(parent),
  9     ui(new Ui::TcpClient)
 10 {
 11     ui->setupUi(this);
 12     setWindowTitle(tr("TCP Client"));
 13 
 14     contentListWidget = new QListWidget;
 15 
 16     sendLineEdit = new QLineEdit;
 17     sendBtn = new QPushButton(tr("发送"));
 18 
 19     userNameLabel=new QLabel(tr("用户名:"));
 20     userNameLineEdit = new QLineEdit;
 21 
 22     serverIPLabel = new QLabel(tr("服务器地址: "));
 23     serverIPLineEdit = new QLineEdit;
 24 
 25     portLabel = new QLabel(tr("端口: "));
 26     portLineEdit = new QLineEdit;
 27 
 28     enterBtn = new QPushButton(tr("进入聊天室"));
 29 
 30     mainLayout = new QGridLayout(this);
 31     mainLayout->addWidget(contentListWidget,0,0,1,2);
 32     mainLayout->addWidget(sendLineEdit,1,0);
 33     mainLayout->addWidget(sendBtn,1,1);
 34     mainLayout->addWidget(userNameLabel,2,0);
 35     mainLayout->addWidget(userNameLineEdit,2,1);
 36     mainLayout->addWidget(serverIPLabel,3,0);
 37     mainLayout->addWidget(serverIPLineEdit,3,1);
 38     mainLayout->addWidget(portLabel,4,0);
 39     mainLayout->addWidget(portLineEdit,4,1);
 40     mainLayout->addWidget(enterBtn,5,0,1,2);
 41 
 42     status = false;
 43 
 44     port = 8010;
 45 
 46     portLineEdit->setText(QString::number(port));
 47 
 48     serverIP=new QHostAddress();
 49 
 50     connect(enterBtn,SIGNAL(clicked(bool)),this,SLOT(slotEnter()));
 51     connect(sendBtn,SIGNAL(clicked(bool)),this,SLOT(slotSend()));
 52 
 53     sendBtn->setEnabled(false);
 54 }
 55 
 56 TcpClient::~TcpClient()
 57 {
 58     delete ui;
 59 }
 60 
 61 void TcpClient::slotEnter()
 62 {
 63     //status表示当前的状态,true表示已经进入聊天室,false表示已经离开聊天室
 64     //这里根据status的状态决定是进入还是离开操作
 65     if(!status)
 66     {
 67         //完成输入合法性检验
 68         QString ip = serverIPLineEdit->text();
 69         //用来判断给定的IP地址是否能够被正确解析
 70         if(!serverIP->setAddress(ip))
 71         {
 72             QMessageBox::information(this,tr("error"),tr("server ip address error!"));
 73             return;
 74         }
 75 
 76         if(userNameLineEdit->text()=="")
 77         {
 78             QMessageBox::information(this,tr("error"),tr("User name error!"));
 79             return;
 80         }
 81 
 82         userName = userNameLineEdit->text();
 83 
 84         //创建QTcpSocket类对象,并将信号/槽连接起来
 85         tcpSocket = new QTcpSocket(this);
 86         connect(tcpSocket,SIGNAL(connected()),this,SLOT(slotConnected()));
 87         connect(tcpSocket,SIGNAL(disconnected()),this,SLOT(slotDisconnected()));
 88         connect(tcpSocket,SIGNAL(readyRead()),this,SLOT(dataReceived()));
 89 
 90         //与TCP服务器端连接,连接成功后发出connected
 91         tcpSocket->connectToHost(*serverIP,port);
 92 
 93         status = true;
 94     }
 95     else
 96     {
 97         int length = 0;
 98         //构建一条离开聊天室的消息
 99         QString msg = userName + tr(":Leave Chat Room");
100         //通知服务器端以上构造的消息
101         if( ( length=tcpSocket->write( msg.toLatin1(),msg.length() )  )!=msg.length())
102         {
103             return;
104         }
105 
106         //与服务器端口连接,断开后发出disconnected()信号
107         tcpSocket->disconnectFromHost();
108 
109         //将status状态复位
110         status = false;
111     }
112 }
113 
114 //当服务器连上成功后,客户端构造一条进入聊天室的消息,并通知服务器
115 void TcpClient::slotConnected()
116 {
117     qDebug() << "进入服务器" << endl;
118     sendBtn->setEnabled(true);
119     enterBtn->setText(tr("离开"));
120 
121     int length=0;
122 
123     QString msg = userName+tr("Enter Chat Room");
124     if((length=tcpSocket->write(msg.toLatin1(),msg.length()))!=msg.length())
125     {
126         qDebug() << "发送失败" << endl;
127         return;
128     }
129     else
130     {
131         qDebug() << "发送成功" << endl;
132     }
133 }
134 
135 void TcpClient::slotDisconnected()
136 {
137     sendBtn->setEnabled(false);
138     enterBtn->setText(tr("进入聊天室"));
139 }
140 
141 //当有数据到来时触发此函数,从套接字中将有效数据提出并显示
142 void TcpClient::dataReceived()
143 {
144     while(tcpSocket->bytesAvailable()>0)
145     {
146         QByteArray datagram;
147         datagram.resize(tcpSocket->bytesAvailable());
148 
149         tcpSocket->read(datagram.data(),datagram.size());
150 
151         QString msg = datagram.data();
152         contentListWidget->addItem(msg.left(datagram.size()));
153     }
154 }
155 
156 void TcpClient::slotSend()
157 {
158     if(sendLineEdit->text()=="")
159     {
160         return;
161     }
162 
163     QString msg=userName+":"+sendLineEdit->text();
164 
165     tcpSocket->write(msg.toLatin1(),msg.length());
166     sendLineEdit->clear();
167 }

main.cpp

 1 #include "tcpclient.h"
 2 #include <QApplication>
 3 
 4 int main(int argc, char *argv[])
 5 {
 6     QApplication a(argc, argv);
 7     TcpClient w;
 8     w.show();
 9 
10     return a.exec();
11 }

4　　网页浏览实例

　　首先创建一个QNetworkAccessManager类的实例,它用来发送网络请求和接收应答.然后关联了管理器的finished信号和自定义的槽,每当网络应答结束时都会发射这个信号.最后使用了get函数来发送一个网络请求,网络请求使用QNetwrokRequest类表示,get()函数返回一个QNetworkReply对象

mainwindow.h

 1 #ifndef MAINWINDOW_H
 2 #define MAINWINDOW_H
 3 
 4 #include <QMainWindow>
 5 
 6 #include <QNetworkReply>
 7 #include <QNetworkAccessManager>
 8 class QNetworkAccessManager;
 9 
10 namespace Ui {
11 class MainWindow;
12 }
13 
14 class MainWindow : public QMainWindow
15 {
16     Q_OBJECT
17 
18 public:
19     explicit MainWindow(QWidget *parent = 0);
20     ~MainWindow();
21 
22 private slots:
23     void replyFinished(QNetworkReply *);
24 
25 
26 private:
27     Ui::MainWindow *ui;
28 
29     QNetworkAccessManager *manager;
30 };
31 
32 #endif // MAINWINDOW_H

mainwindow.cpp

 1 #include "mainwindow.h"
 2 #include "ui_mainwindow.h"
 3 
 4 #include <QtNetwork>
 5 
 6 
 7 MainWindow::MainWindow(QWidget *parent) :
 8     QMainWindow(parent),
 9     ui(new Ui::MainWindow)
10 {
11     ui->setupUi(this);
12 
13     //创建QNetworkAccessManager类的实例,它用来发送网络请求和接收应答.然后
14     //管理了管理器的finished()信号和自定义的槽,每当网络应答结束时都会发射
15     //这个信号.最后使用了get()函数来发送一个网络请求,网络请求使用QNetworkRequest
16     //类表示,get()函数返回一个QNetworkReply对象
17     manager = new QNetworkAccessManager(this);
18     connect(manager,SIGNAL(finished(QNetworkReply*)),this,
19             SLOT(replyFinished(QNetworkReply*)));
20     manager->get(QNetworkRequest(QUrl("http://www.baidu.com")));
21 }
22 
23 MainWindow::~MainWindow()
24 {
25     delete ui;
26 }
27 
28 void MainWindow::replyFinished(QNetworkReply *reply)
29 {
30     QString all = reply->readAll();
31     ui->textBrowser->setText(all);
32     reply->deleteLater();
33 }

main.cpp

 1 #include "mainwindow.h"
 2 #include <QApplication>
 3 
 4 int main(int argc, char *argv[])
 5 {
 6     QApplication a(argc, argv);
 7     MainWindow w;
 8     w.show();
 9 
10     return a.exec();
11 }

文件下载示例

mianwindow.h

 1 #ifndef MAINWINDOW_H
 2 #define MAINWINDOW_H
 3 
 4 #include <QMainWindow>
 5 
 6 #include <QNetworkReply>
 7 #include <QNetworkAccessManager>
 8 class QNetworkAccessManager;
 9 
10 #include <QUrl>
11 class QFile;
12 
13 namespace Ui {
14 class MainWindow;
15 }
16 
17 class MainWindow : public QMainWindow
18 {
19     Q_OBJECT
20 
21 public:
22     explicit MainWindow(QWidget *parent = 0);
23     ~MainWindow();
24 
25     void startRequest(QUrl url);
26 
27 private slots:
28     void replyFinished(QNetworkReply *);
29     void httpFinished();
30     void httpReadyRead();
31     void updateDataReadProgress(qint64,qint64);
32 
33 
34     void on_pushButton_clicked();
35 
36 private:
37     Ui::MainWindow *ui;
38 
39     QNetworkAccessManager *manager;
40 
41     QNetworkReply *reply;
42     QUrl url;
43     QFile *file;
44 };
45 
46 #endif // MAINWINDOW_H

mainwindow.cpp

  1 #include "mainwindow.h"
  2 #include "ui_mainwindow.h"
  3 
  4 #include <QtNetwork>
  5 
  6 
  7 MainWindow::MainWindow(QWidget *parent) :
  8     QMainWindow(parent),
  9     ui(new Ui::MainWindow)
 10 {
 11     ui->setupUi(this);
 12 
 13     //创建QNetworkAccessManager类的实例,它用来发送网络请求和接收应答.然后
 14     //管理了管理器的finished()信号和自定义的槽,每当网络应答结束时都会发射
 15     //这个信号.最后使用了get()函数来发送一个网络请求,网络请求使用QNetworkRequest
 16     //类表示,get()函数返回一个QNetworkReply对象
 17     manager = new QNetworkAccessManager(this);
 18     connect(manager,SIGNAL(finished(QNetworkReply*)),this,
 19             SLOT(replyFinished(QNetworkReply*)));
 20 //    manager->get(QNetworkRequest(QUrl("http://www.baidu.com")));
 21 
 22     //ui->progressBar->hide();
 23 }
 24 
 25 MainWindow::~MainWindow()
 26 {
 27     delete ui;
 28 }
 29 
 30 void MainWindow::startRequest(QUrl url)
 31 {
 32     //使用get()函数发送网络请求
 33     reply = manager->get(QNetworkRequest(url));
 34     //readyRead()信号继承自QIODevice类,每当有新的数据可以读取时,都会发射该信号
 35     connect(reply,SIGNAL(readyRead()),this,SLOT(httpReadyRead()));
 36 
 37     //每当网络请求的下载进度更新时都会发射downloadProgress()信号,用于更新进度条;
 38     connect(reply,SIGNAL(downloadProgress(qint64,qint64)),this,
 39             SLOT(updateDataReadProgress(qint64,qint64)));
 40 
 41     //每当应答处理结束时,都会发射finished()信号
 42     connect(reply,SIGNAL(finished()),this,SLOT(httpFinished()));
 43 }
 44 
 45 void MainWindow::replyFinished(QNetworkReply *reply)
 46 {
 47     QString all = reply->readAll();
 48     ui->textBrowser->setText(all);
 49     reply->deleteLater();
 50 }
 51 
 52 //完成下载后,重新隐藏进度条,删除reply和file对象
 53 void MainWindow::httpFinished()
 54 {
 55     ui->progressBar->hide();
 56     file->flush();
 57     file->close();
 58     reply->deleteLater();
 59     reply = 0;
 60     delete file;
 61     file = 0;
 62 }
 63 
 64 //首先判断是否创建了文件,如果是,则读取返回的所有数据,然后写入文件中.
 65 //该文件示后面的下载按钮单机信号槽中创建并打开的
 66 void MainWindow::httpReadyRead()
 67 {
 68     if(file)
 69     {
 70         file->write(reply->readAll());
 71     }
 72 }
 73 
 74 //设置进度条的最大值和当前值
 75 void MainWindow::updateDataReadProgress(qint64 bytesRead, qint64 totalBytes)
 76 {
 77     ui->progressBar->setMaximum(totalBytes);
 78     ui->progressBar->setValue(bytesRead);
 79 }
 80 
 81 //使用要下载的文件名创建了本地文件,使用输入的url进行网络请求,并显示进度条
 82 void MainWindow::on_pushButton_clicked()
 83 {
 84     url = ui->lineEdit->text();
 85     QFileInfo info(url.path());
 86     QString fileName(info.fileName());
 87     qDebug() << fileName<<endl;
 88     file = new QFile(fileName);
 89 
 90     if(!file->open(QIODevice::WriteOnly))
 91     {
 92         qDebug()<<"file open error";
 93         delete file;
 94         file = 0;
 95         return;
 96     }
 97     startRequest(url);
 98     ui->progressBar->setValue(0);
 99     ui->progressBar->show();
100 }

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原文地址：https://www.cnblogs.com/xiaochi/p/8831465.html