#
import sys
import thread,socket
from PyQt4 import QtCore,QtGui
HOST='localhost'
PORT= 50008 
class InstanceChecker(QtCore.QThread):
    ''' class detects second copy of program in memory.
    '''
    def __init__(self, parent=None):
        super(InstanceChecker, self).__init__(parent)
    def run(self):
        self.InstallSocketHandler()
        
    def SendData(self):
        ''' call this method to send data to first running instance
        '''
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        s.connect((HOST, PORT))
        s.send('Hello first copy!.This is from second copy!')
        s.close()
        
    def InstallSocketHandler(self):
        print "creating local socket..."
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.connectionStatus = False
        try:
            s.bind((HOST, PORT))
            self.connectionStatus=True
        except socket.error:
            print "socket error!"
            # send data through socket to first copy
            self.SendData()
            self.emit(QtCore.SIGNAL("status"),'busy')
        if self.connectionStatus:
            self.emit(QtCore.SIGNAL("status"),'ok')
            s.listen(1)
            while 1:
                conn, addr = s.accept()
                data = conn.recv(1024)
                self.emit(QtCore.SIGNAL("datareceived"),data)
                if data == 'end': break
            conn.close()


def datareceiver(data):
    print "receiving data from second copy :",data
    # raise window from minimized(possibly) state
    form.showNormal()
def signalreceiver(data):
    print "signal received:",data
    if data == 'busy':
        print "First copy detected in memory : exiting now."
        sys.exit(1)

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    app.instanceChecker = InstanceChecker()
    app.instanceChecker.start()
    

    app.connect(app.instanceChecker,QtCore.SIGNAL("status"),signalreceiver)
    app.connect(app.instanceChecker,QtCore.SIGNAL("datareceived"),datareceiver)

    global form
    form = QtGui.QMainWindow(None)
    form.show()
    app.exec_()