Server - Socket to receive XML messages, dialog problem

Hello,

I get into the receiving routine.

But pThis is NULL
and
UpdateReceiveEdit
causes an exception.
What can the solution look like and what is the cause?

ServerSocket_cpp.TXT

ServerSocket_h.TXT

WrapperSocketDlg_cpp.TXT

WrapperSocketDlg_h.TXT

https://1drv.ms/u/s!AkxC5fEcJdT1dWvN3AH-eMusXho?e=Z9Osyc

void CWSocketDlg::ReceiveCallback(char* buffer, int length)
{
	CWSocketDlg* pThis = (CWSocketDlg*)AfxGetMainWnd();
	pThis->UpdateReceiveEdit(buffer, length);
	CString str(buffer, length);
	pThis->m_receiveEdit.SetWindowText(str);
}
void CWSocketDlg::UpdateReceiveEdit(char* buffer, int length)
{
	//CString str(buffer, length);
	//m_receiveEdit.SetWindowText(str);
	//UpdateData(false);	
}