code: def node(self,port, hub_address=("localhost", 4444)):
          ''' java -jar selenium-server.jar -role node -port 5555 -hub http://127.0.0.1:4444/grid/register/
          @param port:  listen port of selenium node
          @param hub_address: hub address which node will connect to 
          '''
          self._ip, self._port = hub_address
          self.command = [self._conf["java_path"], "-jar", self._conf["jar_path"], "-port", str(port), "-role", "node", "-hub", "http://%s:%s/grid/register/" %(self._ip, self._port)]        
          return self node(self,port, hub_address=("localhost", 4444)):
          ''' java -jar selenium-server.jar -role node -port 5555 -hub http://127.0.0.1:4444/grid/register/
          @param port:  listen port of selenium node
          @param hub_address: hub address which node will connect to 
          '''
          self._ip, self._port = hub_address
          self.command = [self._conf["java_path"], "-jar", self._conf["jar_path"], "-port", str(port), "-role", "node", "-hub", "http://%s:%s/grid/register/" %(self._ip, self._port)]        
          return self
docs: java -jar selenium-server.jar -role node -port 5555 -hub http://127.0.0.1:4444/grid/register/
          @param port:  listen port of selenium node
          @param hub_address: hub address which node will connect to