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A lot of arduino shields are equipped with GSM/GPS antenna, which can achieve the function of sending text or gps positioning and so on.
On the other hand, other wifi module is also play an important role in the communication.
Both the former and the latter can be applied to the IOT project and work well with arduino. In IOT project, it is easy to find that the arduino shield can used to identify, perceive and collect information of objects, but the wifi module is used to share and distribute information.