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);