I am trying to connect to a FTP server on a raspberry pi and transfer a file onto the server. I am using the SIM5320A chip on a breakout module and I am having trouble getting the module to connect to the server. I have forwarded the proper FTP port (21) on the router that the pi is connected to and I also have the vsftpd set up on the pi (which is a FTP linux program). I have tested the ftp server by transferring something from an ftp client on my computer to the ftp server on the pi and it works. I will post the commands I used as well as some of my thoughts. Please help me out and give me feedback.
AT+CGSOCKCONT=1,"IP","fast.t-mobile.com" (something I am not sure about is the apn, does anyone know if this one for tmobile is correct? I can't find that much information online)
AT+CFTPPUT="/files/fromcell.txt" - At this point i should be prompted to enter the text that is going to be in this txt file after I save, but instead of prompting me, the module waits while the red light on it flashes 200 ms on and 200 ms off which is supposed to mean that the data connection I requested is active. It then gives me an error that says "+CFTPPUT: 215" and this error code means "failed to connect socket".
Does anyone have any insight on what the APN is and how it should be set? I can't seem to find much else information on how to set it online.