使用UDP协议和readDatagram接收数据 [英] Receive data with UDP protocol and readDatagram
本文介绍了使用UDP协议和readDatagram接收数据的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
在帮助我使用UDP协议向某人正确发送数据的第一个主题后，我在接收这些数据时遇到问题。这个问题很奇怪，只发生在我第一次启动发送数据的功能。第一次，服务器只接收第一帧。
下面是通过UDP协议发送数据的代码（我的数据是一个结构体）：
void MyUDP :: sendUDP（）
{
//发送结构
typedef struct MyStructTag
{
int test1;
bool test2;
char test3;
} MyStruct;
MyStruct envoie;
envoie.test1 = 1;
envoie.test2 = true;
envoie.test3 = 97;
//将数据报数据报
//发送到主机地址和端口。
// qint64 QUdpSocket :: writeDatagram（const QByteArray& datagram，
// const QHostAddress& host，quint16 port）
QByteArray buf;
QDataStream s（& buf，QIODevice :: WriteOnly）;
//默认情况下，所有系统上的编码都是big endian。你
//可以改变它，如果你愿意。
if（false）s.setByteOrder（QDataStream :: LittleEndian）;
s<< （qint32）envoie.test1<< （quint8）envoie.test2< （qint8）envoie.test3;
//我发送5帧
socket-> writeDatagram（buf，QHostAddress（10.100.14.79），4000）;
socket-> writeDatagram（buf，QHostAddress（10.100.14.79），4000）;
socket-> writeDatagram（buf，QHostAddress（10.100.14.79），4000）;
socket-> writeDatagram（buf，QHostAddress（10.100.14.79），4000）;
socket-> writeDatagram（buf，QHostAddress（10.100.14.79），4000）;
}
这里的函数允许我接收这些数据：
void MyUDP :: readyRead（）
{
QHostAddress sender;
quint16 senderPort;
// qint64 QUdpSocket :: readDatagram（char * data，qint64 maxSize，
// QHostAddress * address = 0，quint16 * port = 0）
//接收数据报不大于maxSize字节并将其存储在数据中。
//发件人的主机地址和端口存储在* address和* port
//（除非指针为0）。
typedef struct MyStructTag
{
int test1;
bool test2;
char test3;
} MyStruct;
MyStruct recois;
socket-> readDatagram（（char *）& recois，sizeof（recois），& sender，& senderPort）;
qDebug（）<< Message from：<< sender.toString（）;
qDebug（）<< 消息端口：< senderPort;
qDebug（）<< Message：<< recois.test3;
}
为什么我第一次启动sendUDP时只收到1帧？ p>
解决方案
有两个问题：
-
在
必须在发送时使用readyRead中，您必须循环socket-> hasPendingDatagrams（）QDataStream和接收端。
最后，您正在编写C ++，不应使用C结构语法。使结构声明重复也是适得其反。您需要的是让 MyStruct
下面是一个完整的示例。
#include< QCoreApplication>
#include< QUdpSocket>
#include< QDataStream>
#include< QBasicTimer>
static const quint16 port = 4000;
class MyUDP：public QObject {
Q_OBJECT
QUdpSocket m_socket;
QBasicTimer m_timer;
void timerEvent（QTimerEvent * ev）{
if（ev-> timerId（）！= m_timer.timerId（））return;
sendUDP（）;
}
void sendUDP（）;
public：
MyUDP（）{
m_timer.start（1000，this）;
connect（& m_socket，SIGNAL（readyRead（）），SLOT（readyRead（）））;
m_socket.bind（QHostAddress :: LocalHost，port）;
}
Q_SLOT void readyRead（）;
};
struct MyStruct {
int test1;
bool test2;
char test3;
MyStruct（）{}
MyStruct（int t1，bool t2，char t3）：test1（t1），test2（t2），test3（t3）{}
};
template< typename T> T get（QDataStream& str）{
T value;
str>>值;
返回值;
}
QDataStream& operator<<<（QDataStream& str，const MyStruct& m）
{
return str< （qint32）m.test1 < （bool）m.test2 < （qint8）m.test3;
}
QDataStream& >>（QDataStream& str，MyStruct& m）
{
m.test1 = get< qint32>（str）;
m.test2 = get< bool>（str）;
m.test3 = get< qint8>（str）;
return str;
}
void MyUDP :: sendUDP（）
{
MyStruct envoie（1，true，97）;
QByteArray buf;
QDataStream s（& buf，QIODevice :: WriteOnly）;
//默认情况下，所有系统上的编码都是big endian。你
//可以改变它，如果你愿意。
if（false）s.setByteOrder（QDataStream :: LittleEndian）;
s<<恩沃伊
for（int i = 0; i <5; ++ i）{
m_socket.writeDatagram（buf，QHostAddress :: LocalHost，port）;
}
}
void MyUDP :: readyRead（）
{
QHostAddress sender;
quint16 senderPort;
MyStruct recois;
while（m_socket.hasPendingDatagrams（））{
QByteArray buf（m_socket.pendingDatagramSize（），Qt :: Uninitialized）;
QDataStream str（& buf，QIODevice :: ReadOnly）;
m_socket.readDatagram（buf.data（），buf.size（），& sender，& senderPort）;
str>>雷西斯
qDebug（）<< Message from：<<发送者
qDebug（）<< 消息端口：< senderPort;
qDebug（）<< Message：<< recois.test3;
}
}
int main（int argc，char * argv []）
{
QCoreApplication a（argc，argv）;
MyUDP udp;
return a.exec（）;
}
#includemain.moc
After a first topic that help me send correctly data to someone using UDP Protocol, I have a problem in the reception of these data. This problem is very strange and only happen the first time I launch the function for sending data. The first time, the server only receive the first frame. But after, if I re use the function everything is ok.
So here's the code that send data through UDP Protocol (my data is a structure) :
void MyUDP::sendUDP()
{
//Structure to send
typedef struct MyStructTag
{
int test1;
bool test2;
char test3;
} MyStruct;
MyStruct envoie;
envoie.test1 = 1;
envoie.test2 = true;
envoie.test3 = 97;
// Sends the datagram datagram
// to the host address and at port.
// qint64 QUdpSocket::writeDatagram(const QByteArray & datagram,
// const QHostAddress & host, quint16 port)
QByteArray buf;
QDataStream s(&buf, QIODevice::WriteOnly);
// The encoding is big endian by default, on all systems. You
// can change it if you wish.
if (false) s.setByteOrder(QDataStream::LittleEndian);
s << (qint32)envoie.test1 << (quint8)envoie.test2 << (qint8)envoie.test3;
//I'm sending 5 frames
socket->writeDatagram(buf, QHostAddress("10.100.14.79"), 4000);
socket->writeDatagram(buf, QHostAddress("10.100.14.79"), 4000);
socket->writeDatagram(buf, QHostAddress("10.100.14.79"), 4000);
socket->writeDatagram(buf, QHostAddress("10.100.14.79"), 4000);
socket->writeDatagram(buf, QHostAddress("10.100.14.79"), 4000);
}
And here's the function that allow me te receive these data :
void MyUDP::readyRead()
{
QHostAddress sender;
quint16 senderPort;
// qint64 QUdpSocket::readDatagram(char * data, qint64 maxSize,
// QHostAddress * address = 0, quint16 * port = 0)
// Receives a datagram no larger than maxSize bytes and stores it in data.
// The sender's host address and port is stored in *address and *port
// (unless the pointers are 0).
typedef struct MyStructTag
{
int test1;
bool test2;
char test3;
} MyStruct;
MyStruct recois;
socket->readDatagram((char*)&recois, sizeof (recois), &sender, &senderPort);
qDebug() << "Message from: " << sender.toString();
qDebug() << "Message port: " << senderPort;
qDebug() << "Message: " << recois.test3;
}
Why did I only receive 1 frame the first time I launch sendUDP ?
解决方案
There are two problems:
Within the
readyReadyou must loop whilesocket->hasPendingDatagrams()is true.You must use the
QDataStreamon both the sending and the receiving end.
Finally, you are writing C++, you should not use the C structure syntax. It is also counterproductive to have the structure declaration duplicated. What you need is to have the streaming operators for MyStruct.
Below is a complete example.
#include <QCoreApplication>
#include <QUdpSocket>
#include <QDataStream>
#include <QBasicTimer>
static const quint16 port = 4000;
class MyUDP : public QObject {
Q_OBJECT
QUdpSocket m_socket;
QBasicTimer m_timer;
void timerEvent(QTimerEvent*ev) {
if (ev->timerId() != m_timer.timerId()) return;
sendUDP();
}
void sendUDP();
public:
MyUDP() {
m_timer.start(1000, this);
connect(&m_socket, SIGNAL(readyRead()), SLOT(readyRead()));
m_socket.bind(QHostAddress::LocalHost, port);
}
Q_SLOT void readyRead();
};
struct MyStruct {
int test1;
bool test2;
char test3;
MyStruct() {}
MyStruct(int t1, bool t2, char t3) : test1(t1), test2(t2), test3(t3) {}
};
template <typename T> T get(QDataStream & str) {
T value;
str >> value;
return value;
}
QDataStream & operator<<(QDataStream & str, const MyStruct & m)
{
return str << (qint32)m.test1 << (bool)m.test2 << (qint8)m.test3;
}
QDataStream & operator>>(QDataStream & str, MyStruct & m)
{
m.test1 = get<qint32>(str);
m.test2 = get<bool>(str);
m.test3 = get<qint8>(str);
return str;
}
void MyUDP::sendUDP()
{
MyStruct envoie(1, true, 97);
QByteArray buf;
QDataStream s(&buf, QIODevice::WriteOnly);
// The encoding is big endian by default, on all systems. You
// can change it if you wish.
if (false) s.setByteOrder(QDataStream::LittleEndian);
s << envoie;
for (int i = 0; i < 5; ++ i) {
m_socket.writeDatagram(buf, QHostAddress::LocalHost, port);
}
}
void MyUDP::readyRead()
{
QHostAddress sender;
quint16 senderPort;
MyStruct recois;
while (m_socket.hasPendingDatagrams()) {
QByteArray buf(m_socket.pendingDatagramSize(), Qt::Uninitialized);
QDataStream str(&buf, QIODevice::ReadOnly);
m_socket.readDatagram(buf.data(), buf.size(), &sender, &senderPort);
str >> recois;
qDebug() << "Message from: " << sender;
qDebug() << "Message port: " << senderPort;
qDebug() << "Message: " << recois.test3;
}
}
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
MyUDP udp;
return a.exec();
}
#include "main.moc"
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