With the increasing use of robots in various fields, the importance of communication security between robots and their components has become a pressing concern. As the primary development framework for robot applications, ROS2 is replacing ROS1 at a rapid pace, and its security issues have direct implications for the security of robot systems. This paper presents an exploration and study of the communication security issues of ROS2 by combining CIA triad with the ROS2 communication mechanism. We propose the fundamental security requirements of the ROS2 system under different communication mechanisms and provide formal modeling and definition. Moreover, we classify and analyze network attacks at the ROS2 level and implement a tool, ROS2Tester, to conduct modeling the ROS2 formal security modules, penetration testing and evaluating the security of ROS2 systems.