void TCPConnection::startChecking()
{
	// Thread starten
	if(s.IsOpen()) // s is a Socket Connection
	{
		m_terminateThread = false;
		t.Run(THISBACK(cb));
	}
}

void TCPConnection::stopChecking()
{
	// thread beenden
	if(t.IsOpen())
		m_terminateThread = true;
}

void TCPConnection::cb()
{
	while(!m_terminateThread)
	{
		tempBuffer = s.Read(1000);
		
		if(!IsNull(tempBuffer))
		{
			buffer += tempBuffer;
			tempBuffer.Clear();
			WhenDataReceived();
		}
	}
	
	// CloseHandle(t.GetHandle()); // wont work

bool TCPConnection::hasThreadStopped()
{
	return !t.IsOpen();
}

void xxxDlg::onCancel()
{
	if(TcpConnection().s.IsOpen()) // TcpConnection() returns ref on Single<TCPConnection>
	{
		TcpConnection().stopChecking();
		
		while(!TcpConnection().hasThreadStopped())
		{
			Sleep(50); // this is where I stuck... The thread is not closed!!!!!
	 	}
		TcpConnection().s.Close();
	}
	 	
	Break(IDCANCEL);
}

#include <Core/Core.h>
using namespace Upp;

struct TCPConnection {
	bool m_terminateThread;
	bool m_isOpen;
	typedef TCPConnection CLASSNAME;
	
	TCPConnection(): m_terminateThread(false), m_isOpen(false) {}
	void startChecking()
	{
		LOG("thread started");	
		if(!m_isOpen) //do not reopen if already opened
		{
			m_terminateThread = false;
			m_isOpen = true;
			Thread::Start(THISBACK(cb));
		}
	}
	
	void stopChecking()
	{
		m_terminateThread = true;
		LOG("thread told to stop");	
	}
	
	void cb()
	{
		LOG("thread starting");
		while(!m_terminateThread)
		{
			LOG("thread running");
			Sleep(222); // do some "work"
		}
		
		LOG("thread closing");
		m_isOpen = false;
	}
	bool hasThreadStopped()
	{
		LOG("thread checked");	
		return !m_isOpen;
	}
};
 
CONSOLE_APP_MAIN
{
	StdLogSetup(LOG_CERR);
	
	TCPConnection t;
	t.startChecking();
	Sleep(1000);
	t.stopChecking();
	
	while(!t.hasThreadStopped())
	{
		Sleep(50);
	}
	LOG("thread has stopped");	
}