# Conflicts:
#	QTcpClientTest/qtcpclienttest.cpp

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.

2. redirect target exe files to a upper directory "bin"

Sloved a socket-error problem , when socket error happened, some cleaning works should be done immediately

Add a cluster-reconnection method. when cluster nodes lost all connections, it will attempt to re-connect to target cluster every 2 mins

* database confirm method in different threads, maximum 5 seconds /each check
* close current db connection when error take place.

Sloved a serious problem in heavily client login-logoff. add a rubbish can, hold sockets to be deleted later

Simply add a logger class, with the help of which , develpers can re-direct qDebug(), qWarning(), qCritical() and QFatal(...) outputs to log files , instead of stderr.

Add a auto-join cluster method, as soon as the server node be started, a join-cluster approach will be taken.

Add a thread-quitting cleaning method. when a thread is quitting, its finished signal will be caugth,
so that , db resource class can clean the database connections belongs to this thread one by one.
this method is very important in some situation, such as Qt-concurrent threading, threads will be created, deleted frequently.

* sloved multi-thread db access problem. the databaseresource class has been
improved, for each thread, a thread-owned db connection will be cloned from main
db connection.

a bug caused by m_currentBlock.constData() has been fixed. the pointer returned by this method will be unavaliable when the block has been changed.

There is still a problem in heavily-test.

const QByteArray & type paras, will cause lift cycle problems. using Value-pass instead.
----
QString, QByteArray supports ref-count and auto-delete , also, these classes support
least-copying, deep-copy will only take place, when the data is about to be changed.
so, in singnals and slots, using QString, QByteArray instead of const QString & and const QByteArray & ,
will not cause performance problem.

Each server instance knows exactly how many clients each server currently have.