QNetworkDatagram 类提供 UDP (用户数据报协议) 数据报的数据和元数据。 更多...
| 头： | #include <QNetworkDatagram> |
| qmake: | QT += network |
| Since: | Qt 5.8 |
该类在 Qt 5.8 引入。
注意： 此类的所有函数 可重入 .
| QNetworkDatagram (const QNetworkDatagram & other ) | |
| QNetworkDatagram (const QByteArray & data , const QHostAddress & destinationAddress = QHostAddress(), quint16 port = 0) | |
| QNetworkDatagram () | |
| QNetworkDatagram & | operator= (const QNetworkDatagram & other ) |
| void | clear () |
| QByteArray | data () const |
| QHostAddress | destinationAddress () const |
| int | destinationPort () const |
| int | hopLimit () const |
| uint | interfaceIndex () const |
| bool | isNull () const |
| bool | isValid () const |
| QNetworkDatagram | makeReply (const QByteArray & payload ) const & |
| QNetworkDatagram | makeReply (const QByteArray & payload ) && |
| QHostAddress | senderAddress () const |
| int | senderPort () const |
| void | setData (const QByteArray & data ) |
| void | setDestination (const QHostAddress & address , quint16 port ) |
| void | setHopLimit (int count ) |
| void | setInterfaceIndex (uint index ) |
| void | setSender (const QHostAddress & address , quint16 port = 0) |
| void | swap (QNetworkDatagram & other ) |
QNetworkDatagram 可以用于 QUdpSocket 类表示包含在 UDP (用户数据报协议) 数据报中的完整信息。QNetworkDatagram 封装以下数据报信息：
QUdpSocket 将试着在所有操作系统尽可能匹配常见行为，但在某些操作系统无法获得以上所有元数据。无法设置数据报元数据当发送时采用 QUdpSocket::writeDatagram () 会被默默丢弃。
当接待时， senderAddress () 和 senderPort () properties contain the address and port of the peer that sent the datagram, while destinationAddress () 和 destinationPort () contain the target that was contained in the datagram. That is usually an address local to the current machine, but it can also be an IPv4 broadcast address (such as "255.255.255.255") or an IPv4 or IPv6 multicast address. Applications may find it useful to determine if the datagram was sent specifically to this machine via unicast addressing or whether it was sent to multiple destinations.
当发送时， senderAddress () 和 senderPort () should contain the local address to be used when sending. The sender address must be an address that is assigned to this machine, which can be obtained using QNetworkInterface , and the port number must be the port number that the socket is bound to. Either field can be left unset and will be filled in by the operating system with default values. The destinationAddress () 和 destinationPort () fields may be set to a target address different from the one the UDP socket is currently associated with.
Usually, when sending a datagram in reply to a datagram previously received, one will set the destinationAddress () to be the senderAddress () of the incoming datagram and similarly for the port numbers. To facilitate this common process, QNetworkDatagram provides the function makeReply ().
The hopCount() function contains, for a received datagram, the remaining hop count limit for the packet. When sending, it contains the hop count limit to be set. Most protocols will leave this value set to the default and let the operating system decide on the best value to be used. Multicasting over IPv4 often uses this field to indicate the scope of the multicast group (link-local, local to an organization or global).
The interfaceIndex () function contains the index of the operating system's interface that received the packet. This value is the same one that can be set on a QHostAddress::scopeId () property and matches the QNetworkInterface::index () property. When sending packets to global addresses, it is not necessary to set the interface index as the operating system will choose the correct one using the system routing table. This property is important when sending datagrams to link-local destinations, whether unicast or multicast.
Some features of QNetworkDatagram are not supported in all operating systems. Only the address and ports of the remote host (sender in received packets and destination for outgoing packets) are supported in all systems. On most operating systems, the other features are supported only for IPv6. Software should check at runtime whether the rest could be determined for IPv4 addresses.
当前特征的支持如下：
| 操作系统 | 本地地址 | 跳跃计数 | 接口索引 |
|---|---|---|---|
| FreeBSD | 支持 | 支持 | 仅对于 IPv6 |
| Linux | 支持 | 支持 | 支持 |
| OS X | 支持 | 支持 | 仅对于 IPv6 |
| 其它 Unix 支持 RFC 3542 | 仅对于 IPv6 | 仅对于 IPv6 | 仅对于 IPv6 |
| Windows (桌面) | 支持 | 支持 | 支持 |
| Windows RT | 不支持 | 不支持 | 不支持 |
另请参阅 QUdpSocket and QNetworkInterface .
创建新的 QNetworkDatagram representing a reply to this incoming datagram and sets the payload data to payload . This function is a very convenient way of responding to a datagram back to the original sender.
范例：
void Server::readPendingDatagrams()
{
while (udpSocket->hasPendingDatagrams()) {
QNetworkDatagram datagram = udpSocket->receiveDatagram();
QByteArray replyData = processThePayload(datagram.data());
udpSocket->writeDatagram(datagram.makeReply(replyData));
}
}
This function is especially convenient since it will automatically copy parameters from this datagram to the new datagram as appropriate:
若 QNetworkDatagram is modified in a future version of Qt to carry further metadata, this function will copy that metadata as appropriate.
This datagram's destination address is not copied if it is an IPv4 address because it is not possible to tell an IPv4 broadcast address apart from a regular IPv4 address without an exhaustive search of all addresses assigned to this machine. Attempting to send a datagram with the sender address equal to the broadcast address is likely to fail. However, this should not affect the communication as network interfaces with multiple IPv4 addresses are uncommon, so the address the operating system will select will likely be one the peer will understand.
注意： This function comes with both rvalue- and lvalue-reference qualifier overloads, so it is a good idea to make sure this object is rvalue, if possible, before calling makeReply , so as to make better use of move semantics. To achieve that, the example above would use:
udpSocket->writeDatagram(std::move(datagram).makeReply(replyData));
创建副本为 other 数据报，包括负载和元数据。
To create a datagram suitable for sending in a reply, use QNetworkDatagram::makeReply ();
Creates a QNetworkDatagram object and sets data as the payload data, along with destinationAddress and port as the destination address of the datagram.
Creates a QNetworkDatagram object with no payload data and undefined destination address.
可以修改负载通过使用 setData () and the destination address can be set with setDestination ().
If the destination address is left undefined, QUdpSocket::writeDatagram () will attempt to send the datagram to the address last associated with, by using QUdpSocket::connectToHost ().
拷贝 other 数据报，包括负载和元数据。
To create a datagram suitable for sending in a reply, use QNetworkDatagram::makeReply ();
清零负载数据和元数据在此 QNetworkDatagram 对象，将它们重置到其默认值。
Returns the data payload of this datagram. For a datagram received from the network, it contains the payload of the datagram. For an outgoing datagram, it is the datagram to be sent.
Note that datagrams can be transmitted with no data, so the returned QByteArray 可能为空。
另请参阅 setData ().
Returns the destination address associated with this datagram. For a datagram received from the network, it is the address the peer node sent the datagram to, which can either be a local address of this machine or a multicast or broadcast address. For an outgoing datagrams, it is the address the datagram should be sent to.
If no destination address was set on this datagram, the returned object will report true to QHostAddress::isNull ().
另请参阅 senderAddress (), destinationPort ()，和 setDestination ().
Returns the port number of the destination associated with this datagram. For a datagram received from the network, it is the local port number that the peer node sent the datagram to. For an outgoing datagram, it is the peer port the datagram should be sent to.
If no destination address was associated with this datagram, this function returns -1.
另请参阅 destinationAddress (), senderPort ()，和 setDestination ().
Returns the hop count limit associated with this datagram. The hop count limit is the number of nodes that are allowed to forward the IP packet before it expires and an error is sent back to the sender of the datagram. In IPv4, this value is usually known as "time to live" (TTL).
If this datagram was received from the network, this is the remaining hop count of the datagram after reception and was decremented by 1 by each node that forwarded the packet. A value of -1 indicates that the hop limit count not be obtained.
If this is an outgoing datagram, this is the value to be set in the IP header upon sending. A value of -1 indicates the operating system should choose the value.
另请参阅 setHopLimit ().
Returns the interface index this datagram is associated with. The interface index is a positive number that uniquely identifies the network interface in the operating system. This number matches the value returned by QNetworkInterface::index () for the interface.
If this datagram was received from the network, this is the index of the interface that the packet was received from. If this is an outgoing datagram, this is the index of the interface that the datagram should be sent on.
A value of 0 indicates that the interface index is unknown.
另请参阅 setInterfaceIndex ().
返回 true，若此 QNetworkDatagram object is null. This function is the opposite of isValid ().
返回 true，若此 QNetworkDatagram object is valid. A valid QNetworkDatagram object contains at least one sender or receiver address. Valid datagrams can contain empty payloads.
Returns the sender address associated with this datagram. For a datagram received from the network, it is the address of the peer node that sent the datagram. For an outgoing datagrams, it is the local address to be used when sending.
If no sender address was set on this datagram, the returned object will report true to QHostAddress::isNull ().
另请参阅 destinationAddress (), senderPort ()，和 setSender ().
Returns the port number of the sender associated with this datagram. For a datagram received from the network, it is the port number that the peer node sent the datagram from. For an outgoing datagram, it is the local port the datagram should be sent from.
If no sender address was associated with this datagram, this function returns -1.
另请参阅 senderAddress (), destinationPort ()，和 setSender ().
Sets the data payload of this datagram to data . It is usually not necessary to call this function on received datagrams. For outgoing datagrams, this function sets the data to be sent on the network.
由于数据报可以为空，因此空 QByteArray 是有效值对于 data .
另请参阅 data ().
Sets the destination address associated with this datagram to be the address address and port number port . The destination address and port numbers are usually set by QUdpSocket upon reception, so there's no need to call this function on a received datagram.
For outgoing datagrams, this function can be used to set the address the datagram should be sent to. It can be the unicast address used to communicate with the peer or a broadcast or multicast address to send to a group of devices.
另请参阅 QUdpSocket::writeDatagram (), destinationAddress (), destinationPort ()，和 setSender ().
Sets the hop count limit associated with this datagram to count . The hop count limit is the number of nodes that are allowed to forward the IP packet before it expires and an error is sent back to the sender of the datagram. In IPv4, this value is usually known as "time to live" (TTL).
It is usually not necessary to call this function on datagrams received from the network.
If this is an outgoing packet, this is the value to be set in the IP header upon sending. The valid range for the value is 1 to 255. This function also accepts a value of -1 to indicate that the operating system should choose the value.
另请参阅 hopLimit ().
Sets the interface index this datagram is associated with to index . The interface index is a positive number that uniquely identifies the network interface in the operating system. This number matches the value returned by QNetworkInterface::index () for the interface.
It is usually not necessary to call this function on datagrams received from the network.
If this is an outgoing packet, this is the index of the interface the datagram should be sent on. A value of 0 indicates that the operating system should choose the interface based on other factors.
Note that the interface index can also be set with QHostAddress::setScopeId () for IPv6 destination addresses and then with setDestination (). If the scope ID set in the destination address and index are different and neither is zero, it is undefined which interface the operating system will send the datagram on.
另请参阅 interfaceIndex () 和 setInterfaceIndex()。
Sets the sender address associated with this datagram to be the address address and port number port . The sender address and port numbers are usually set by QUdpSocket upon reception, so there's no need to call this function on a received datagram.
For outgoing datagrams, this function can be used to set the address the datagram should carry. The address address must usually be one of the local addresses assigned to this machine, which can be obtained using QNetworkInterface . If left unset, the operating system will choose the most appropriate address to use given the destination in question.
The port number port must be the port number associated with the socket, if there is one. The value of 0 can be used to indicate that the operating system should choose the port number.
另请参阅 QUdpSocket::writeDatagram (), senderAddress (), senderPort ()，和 setDestination ().
交换此实例采用 other .