When my mobile phone sends a message, I have to enter a short message center number. What happened?

The number of SMS centers varies from place to place. First of all, you need to know the principle of texting. Simply put, you make up the short message and send it to the switch, and then forward it to the other party's mobile phone through the switch. There is a process of judging the caller's ownership when you arrive at the SMS gateway. When a mobile phone with a center number sends a short message, it will also send the signaling of the center number to the short message gateway. So it can be sent normally. Please don't care about unprofessional explanations, as long as you can understand them. The number format of the mobile SMS center is: +86 13800 area code (if Chengdu is 028, write 280, the first digit of the four-digit area code is omitted, and the third digit area code is written after 0), and finally it is 500. They are all +8665438+.