MOTO V501 cannot send text messages through the AT command

Recently, I tried to send text messages on the MOTO V501 mobile phone. It was a simple function, but it never worked properly. Later I found the cause of the SMS failure, sending text messages is a function provided by the mobile phone/gprs modem itself. That is to say, you can call a mobile phone. for software, you only need to use the AT command to send the content to the mobile phone. Push/bookmarks are also a type of SMS, but are only binary (HEX) encoded. There is an AT command to control whether the mobile phone displays the input command intact, that is, ATE0 does not display ATE1, Here E is what ECHO means. The problem with V501 is that the ATE command should not affect the display of the AT + CMGS command after the command is executed. The above sign tells the user that the mobile phone is ready, you can continue to transmit the SMS content. After the ECHO is shielded using ATE0, V501 also omits the greater than Mark... I found this problem after comparing it many times. The reproduction method is very simple. Use the Super Terminal to directly open V501, enter CMGF = 0, and then enter AT + CMGS = 30 to see if there will be a greater sign. AT this time, do not send any CTRL + Z to exit. Use ATE0 to disable ECHO, and then input AT + CMGS = 30 to see if there is no greater sign. It's depressing for a long time... As for why I cannot send a PUSH message, it is still strange that I can only check whether other people's software can send a PUSH message. In principle, I can send a general text message to send a PUSH message.
The problem of MMS is a little more complicated. The underlying communication protocols have some relationships with specific mobile phones, mainly reflected in the order and combination. In order to make the program simple, some combinations and sequences are fixed, different modules are slightly different. This should be overcome in my own program, but the RFC documentation is ugly and lazy.