SIM908 - Download FTP file in parts

Question

I am working with the SIM908 GPS/GPRS module. I can make connections to an FTP and download small files without any trouble (given that they are smaller than 60 bytes for example).

I want to download a big file of 1024 bytes and I want to do it in 32 bytes sessions. The AT commands I send are as follows...

ATCOM_FTP_SET_BEARER
ATCOM_FTP_SET_SERVER
ATCOM_FTP_SET_PORT
ATCOM_FTP_SET_USER
ATCOM_FTP_SET_PASSWORD
ATCOM_FTP_SET_SETUP_DOWNLOAD_NAME
ATCOM_FTP_SET_DOWNLOAD_PATH

Then I ask the module to connect:

AT+FTPGET=1

It replies:

OK

+FTPGET:1,1

And then I ask it to read 32 bytes from the 1024 bytes file:

AT+FTPGET=2,32

It replies:

+FTPGET:2,32
12345678901234567890123456789012
OK

The problem is that if I ask only for some bytes from the file, the current FTP operation remains active, the SIM908 is still connected to the FTP and it sends the following lines for a while...

+FTPGET:1,1

+FTPGET:1,1

+FTPGET:1,1

+FTPGET:1,1

After those, the FTP connection times out...

+FTPGET:1,64

I haven't been able to find a "FTP GET CLOSE" command so that I can resume the connection later. I tried sending the following commands but they are replied with an ERROR...

AT+FTPGET=2,0

ERROR

AT+FTPGET=1,0

ERROR

AT+FTPGET=1,1

ERROR

AT+FTPGET=2

ERROR

AT+FTPGET=0

ERROR

There is a command which helps to restore a connection AT+FTPREST=x, where x is the index from we want to start reading the file when it's opened again, but my problem is that I cannot close the previous connection.

I am using the SIM908 AT Command manual v1.02.

http://www.4shared.com/archive/A49KthrTce/SIM908_AT_Command_Manual_V102.html

I cannot download the full 1024 bytes file since I need to do other stuff with the FTP, I am multitasking other FTP functions.

Do you know how to close an FTP download?

Thanks.

PS I am using a PIC microcontroller with C to read/send the commands, but I can test them with a terminal as well.

Answer 1

I contacted a SIM908 distributor. There is no FTP GET CLOSE command in the SIM908 hardware. A workaround to clse the FTP session is to close the APN connection.

AT+SAPBR=0,1

But that does not help. Restoring the APN connection takes a while and the DNS servers are not updated as quickly as I would want them to.

So disappointing.