Can not transfer file using 3G/GPRS

Dear madam/sir,

The detail of my question is that I developed an android spark to send and receive voice file through openfire3.7.1.

The problem is when I connect the server with Wifi, the file can be sent and received successfully, but when I switch to 3G/GPRS/EDGE, the file cannot be sent and received, and if I send a text message via 3G/GPRS/EDGE, It is OK.

I want to know the difference of connection between wifi and 3G/GPRS when sending files, is there any configurations on the server or something else?

I will tremendously appreciate your enlightenment and your help! Thank you!!