Simple chat example. How can I make a list of participants?

[Luga]

Hi everyone!
I need to make a chat. On your site I found an example. But there's no list of participants. How can I do?

Do I understand that the data on a server need to send in that format?
And if the server receives GRTNG, it verifies the existence of party with the same name and save it.?

QByteArray arrBlock;
QDataStream out (& arrBlock, QIODevice:: WriteOnly);
out.setVersion (QDataStream:: Qt_4_5);
out <<quint16 (0) << QString("GRTNG") << nick->text ();
out.device () -> seek (0);
out <<quint16 (arrBlock.size () - sizeof (quint16));
socket-> write (arrBlock);

QByteArray arrBlock;
QDataStream out (& arrBlock, QIODevice:: WriteOnly);
out.setVersion (QDataStream:: Qt_4_5);
out <<quint16 (0) << QString("GRTNG") << nick->text ();
out.device () -> seek (0);
out <<quint16 (arrBlock.size () - sizeof (quint16));
socket-> write (arrBlock);

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and

QByteArray arrBlock;
QDataStream out (& arrBlock, QIODevice:: WriteOnly);
out.setVersion (QDataStream:: Qt_4_5);
out <<quint16 (0) << QString("MSG") << message->text ();
out.device () -> seek (0);
out <<quint16 (arrBlock.size () - sizeof (quint16));
socket-> write (arrBlock);

QByteArray arrBlock;
QDataStream out (& arrBlock, QIODevice:: WriteOnly);
out.setVersion (QDataStream:: Qt_4_5);
out <<quint16 (0) << QString("MSG") << message->text ();
out.device () -> seek (0);
out <<quint16 (arrBlock.size () - sizeof (quint16));
socket-> write (arrBlock);

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I am sorry for my bad English. I hope you understand me.