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：

class UDPServer:public QObject
{
	Q_OBJECT
public:
	UDPServer(QObject *parent = NULL);
	~UDPServer();
private slots:
	void readPendingDatagrams();
private:
	QUdpSocket           *udpSocket;
	
};

UDPServer::UDPServer(QObject *parent /* = NULL */):QObject(parent)
{
	udpSocket = new QUdpSocket(this);
	udpSocket->bind(QHostAddress::LocalHost, 7755);
	cout<<"Server is Running......"<<endl;
	connect(udpSocket, SIGNAL(readyRead()),this, SLOT(readPendingDatagrams()));
}

UDPServer::~UDPServer()
{

}

void UDPServer::readPendingDatagrams()
{
	QHostAddress sender;
	quint16 senderPort;
	while (udpSocket->hasPendingDatagrams()) 
	{
		QByteArray datagram;
		datagram.resize(udpSocket->pendingDatagramSize());
		udpSocket->readDatagram(datagram.data(), datagram.size(),&sender, &senderPort);
		string strMes(datagram);
		std::cout<<strMes<<endl;
	}
	QString text = "hello ...";
	QByteArray datagram = text.toLocal8Bit();
	udpSocket->writeDatagram(datagram.data(),datagram.size(),sender, senderPort);
}

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

   udpSocket->bind(QHostAddress::LocalHost, 7755);

2. 给客户端回发信息

   udpSocket->writeDatagram(datagram.data(),datagram.size(),sender, senderPort);

客户端代码：

class UdpClient : public QWidget
{
	Q_OBJECT

public:
	UdpClient(QWidget *parent = 0, Qt::WFlags flags = 0);
	~UdpClient();

private slots:
	void sendMessageSlot();
	void readPendingDatagrams();
private:
	QUdpSocket     *udpSocket;
	QLineEdit      *m_pLEdit;
	QPushButton    *m_pSendMesBtn;
	QLabel         *m_pMessage;
	//Ui::UdpClientClass ui;
};

UdpClient::UdpClient(QWidget *parent, Qt::WFlags flags)
	: QWidget(parent, flags)
{
	m_pLEdit = new QLineEdit(this);
	m_pSendMesBtn = new QPushButton(tr("Sending"),this);
	udpSocket = new QUdpSocket(this);
	m_pMessage = new QLabel(this);
	QHostAddress sender = udpSocket->localAddress();
	quint16 senderPort = udpSocket->localPort();
	udpSocket->bind(sender,senderPort);
	m_pLEdit->setGeometry(5,5,100,20);
	m_pSendMesBtn->setGeometry(110,5,50,20);
	m_pMessage->setGeometry(5,30,150,20);
	m_pLEdit->setStyleSheet("QLineEdit{color:red}");
	connect(m_pSendMesBtn, SIGNAL(clicked()),this, SLOT(sendMessageSlot()));
	connect(udpSocket, SIGNAL(readyRead()),this, SLOT(readPendingDatagrams()));
	
	//ui.setupUi(this);
	
}

UdpClient::~UdpClient()
{

}

void UdpClient::sendMessageSlot()
{
	QString text = m_pLEdit->text();
	QByteArray datagram = text.toLocal8Bit();
	udpSocket->writeDatagram(datagram.data(),datagram.size(),QHostAddress::LocalHost, 7755);
}

void UdpClient::readPendingDatagrams()
{
	while (udpSocket->hasPendingDatagrams()) 
	{
		QByteArray datagram;
		datagram.resize(udpSocket->pendingDatagramSize());
		QHostAddress sender;
		quint16 senderPort;
		udpSocket->readDatagram(datagram.data(), datagram.size(),&sender, &senderPort);
		QString text = QString(datagram);
		m_pMessage->setText(text);
	}
}

说明：

1.  绑定本地地址和端口，以接收客户端发过来的信息

   QHostAddress sender = udpSocket->localAddress();
   quint16 senderPort = udpSocket->localPort();
   udpSocket->bind(sender,senderPort);

演示结果图：