How to realize the principle of receiving verification code for mobile phone short messages?

The principle of SMS- short message service is simple, but the process of inputting characters on mobile phone is more troublesome. SMS has two outstanding advantages: the first is the store-and-forward mechanism. Sending data packets by SMS is done by the short message center in the mobile network instead of the end user. If the user is not in the service area, the short message is stored in the short message center and forwarded to him after the user appears, which is not available in GPRS and other services. The second is the delivery confirmation mechanism. In the circuit-switched data environment, the connection is end-to-end, so users can know whether the connection is completed and the data transmission situation. However, in the GPRS environment, the terminal connected to the GPRS bearer is always on, and it is always ready to send or receive data transparently (relative to the user). In this way, the task of checking whether the data packet is sent successfully falls on the user, and the corresponding cost will be higher for each packet data service.