QUdpSocket 简单用法

UDP是无连接的不可靠的传输协议，可以用在可靠传输不是很重要的情况下使用。
QUdpSocket是QAbstractSocket 的子类，它们都继承了QIODevice。所以可以用QUdpSocket进行发送接收数据。它和QTcpSocket最大的区别也就是，发送数据之前不需要建立连接。

以下简单例子，演示了用QUdpSocket如何实现客户端和服务端的通信。
服务端代码：

[cpp] view plain copy
  1. class UDPServer:public QObject  
  2. {  
  3.     Q_OBJECT  
  4. public:  
  5.     UDPServer(QObject *parent = NULL);  
  6.     ~UDPServer();  
  7. private slots:  
  8.     void readPendingDatagrams();  
  9. private:  
  10.     QUdpSocket           *udpSocket;  
  11.       
  12. };  

[cpp] view plain copy
  1. UDPServer::UDPServer(QObject *parent /* = NULL */):QObject(parent)  
  2. {  
  3.     udpSocket = new QUdpSocket(this);  
  4.     udpSocket->bind(QHostAddress::LocalHost, 7755);  
  5.     cout<<"Server is Running......"<<endl;  
  6.     connect(udpSocket, SIGNAL(readyRead()),this, SLOT(readPendingDatagrams()));  
  7. }  
  8.   
  9. UDPServer::~UDPServer()  
  10. {  
  11.   
  12. }  
  13.   
  14. void UDPServer::readPendingDatagrams()  
  15. {  
  16.     QHostAddress sender;  
  17.     quint16 senderPort;  
  18.     while (udpSocket->hasPendingDatagrams())   
  19.     {  
  20.         QByteArray datagram;  
  21.         datagram.resize(udpSocket->pendingDatagramSize());  
  22.         udpSocket->readDatagram(datagram.data(), datagram.size(),&sender, &senderPort);  
  23.         string strMes(datagram);  
  24.         std::cout<<strMes<<endl;  
  25.     }  
  26.     QString text = "hello ...";  
  27.     QByteArray datagram = text.toLocal8Bit();  
  28.     udpSocket->writeDatagram(datagram.data(),datagram.size(),sender, senderPort);  
  29. }  

说明：
  1.     我都是在自己的机器上测试，所以服务器地址都是localHost。即
[cpp] view plain copy
      udpSocket->bind(QHostAddress::LocalHost, 7755);  
  2. 给客户端回发信息
[cpp] view plain copy
      udpSocket->writeDatagram(datagram.data(),datagram.size(),sender, senderPort);  

客户端代码：

[cpp] view plain copy
  1. class UdpClient : public QWidget  
  2. {  
  3.     Q_OBJECT  
  4.   
  5. public:  
  6.     UdpClient(QWidget *parent = 0, Qt::WFlags flags = 0);  
  7.     ~UdpClient();  
  8.   
  9. private slots:  
  10.     void sendMessageSlot();  
  11.     void readPendingDatagrams();  
  12. private:  
  13.     QUdpSocket     *udpSocket;  
  14.     QLineEdit      *m_pLEdit;  
  15.     QPushButton    *m_pSendMesBtn;  
  16.     QLabel         *m_pMessage;  
  18. };  
[cpp] view plain copy
  1. UdpClient::UdpClient(QWidget *parent, Qt::WFlags flags)  
  2.     : QWidget(parent, flags)  
  3. {  
  4.     m_pLEdit = new QLineEdit(this);  
  5.     m_pSendMesBtn = new QPushButton(tr("Sending"),this);  
  6.     udpSocket = new QUdpSocket(this);  
  7.     m_pMessage = new QLabel(this);  
  8.     QHostAddress sender = udpSocket->localAddress();  
  9.     quint16 senderPort = udpSocket->localPort();  
  10.     udpSocket->bind(sender,senderPort);  
  11.     m_pLEdit->setGeometry(5,5,100,20);  
  12.     m_pSendMesBtn->setGeometry(110,5,50,20);  
  13.     m_pMessage->setGeometry(5,30,150,20);  
  14.     m_pLEdit->setStyleSheet("QLineEdit{color:red}");  
  15.     connect(m_pSendMesBtn, SIGNAL(clicked()),this, SLOT(sendMessageSlot()));  
  16.     connect(udpSocket, SIGNAL(readyRead()),this, SLOT(readPendingDatagrams()));   19.       
  20. }  
  21.   
  22. UdpClient::~UdpClient()  
  23. {  
  24.   
  25. }  
  26.   
  27. void UdpClient::sendMessageSlot()  
  28. {  
  29.     QString text = m_pLEdit->text();  
  30.     QByteArray datagram = text.toLocal8Bit();  
  31.     udpSocket->writeDatagram(datagram.data(),datagram.size(),QHostAddress::LocalHost, 7755);  
  32. }  
  33.   
  34. void UdpClient::readPendingDatagrams()  
  35. {  
  36.     while (udpSocket->hasPendingDatagrams())   
  37.     {  
  38.         QByteArray datagram;  
  39.         datagram.resize(udpSocket->pendingDatagramSize());  
  40.         QHostAddress sender;  
  41.         quint16 senderPort;  
  42.         udpSocket->readDatagram(datagram.data(), datagram.size(),&sender, &senderPort);  
  43.         QString text = QString(datagram);  
  44.         m_pMessage->setText(text);  
  45.     }  
  46. }  
说明：
  1.  绑定本地地址和端口，以接收客户端发过来的信息
[cpp] view plain copy
      a. QHostAddress sender = udpSocket->localAddress();  
      b. quint16 senderPort = udpSocket->localPort();  
      c. udpSocket->bind(sender,senderPort);