Excuse me, what happened in Infernal Affairs 1 when Andy Lau sent messages to everyone in that area?

Network operators (such as China Mobile and China Unicom) will provide some short message platforms, such as prize quiz, mobile sending to xxxx and Unicom sending to xxxx. Through this platform, you can send short messages to specific users. Infernal Affairs 1 Send a short message to the user at a frequency of 800MHZ.

It may also be a dedicated platform (not necessarily SMS). For some requirements, the platform used by operators for monitoring or control is generally only known by operators and specific institutions, such as the National Security Agency.

Through this platform, you can send short messages like 1860.

In Infernal Affairs, Andy Lau uses a special software to send instructions to the SMS gateway of the network operator (or other interfaces provided by the operator) through the wireless network card of his notebook, and then the operator sends short messages.