Qt Network Broadcasting Question: To get sender IP

There is a simple example about network broadcasting in QtSDK. It is easy to send and receive br开发者_StackOverflow中文版oadcast information. And in the receiver side, I want to know whose broadcast packet I just received. I try QUdpSocket.peerName() in readyRead signal callback function,but I get empty string. Any clue?

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You can retrieve the sender's IP address when reading the packet with QUdpSocket::readDatagram(). You need to pass to readDatagram() a pointer to a QHostAddress in which to store the address:

QHostAddress senderAddress;
yourSocket->readDatagram(&data, size, &senderAddress);
// senderAddress now represents the sender address

You can get the address as a QString or integer from senderAddress if you need to, see the documentation for QHostAddress.

If you want a host name, you can use QHostInfo to do a reverse lookup (but you are not guaranteed to get a name).

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From the docs:

Returns the name of the peer as specified by connectToHost(), or an empty QString if connectToHost() has not been called.

So, if you've called connectToHost() you should get a result. You might also try peerAddress(). Unless you always connect via a name, I wouldn't expect that you'll always be able to do a reverse lookup and get a name.