Add an  extra "quint64" field for ZPnetEngine on bool connectTo (const QHostAddress & address , quint16 nPort,bool bSSLConn, quint64 extraData);
When user call connectTo actively to a remote address, this extra data can be remembered by network engine.
Same extra data value will be taken along with socket handle when
on_connect, on_recieveded or on_sended, on_disconnect... is called.
This approach is well used in another project "dataProxy" in my git resp.