Developing an application that uses TCP/IP over GPRS with permanent mode
If the end user has MMS or WAP-GPRS settings active with the session mode "permanent," he or she is not able to use the application and connect using TCP/IP. This seems to happen because he or she is using the wrong gateway (MMS/WAP). Is this true? If yes, what should be changed to fix the application?
In real life, operators have multiple Access Points (AP) for their subscribers. In the usual setup there are three APs (and settings). One AP is used for WAP, one for MMS, and one for other Internet access.
The WAP AP can only be used for WAP traffic. All traffic is routed to the WAP Gateway that processes the requests and converts the data into a format that is suitable for the WAP browser of the device.
The MMS AP is used to send and receive MMS messages. All traffic from this AP goes trough the WAP Gateway as well, but usually there is a restricted access list and thus the WAP Gateway can only be used to connect to the MMSC.
The third AP is for the Internet. It can be used for any other purpose, such as your application. TCP/IP traffic goes directly to the destination without any gateway interference and this AP is also used when the device works as a modem connected to a PC (for accessing the Internet). The user cannot have multiple ACTIVE APs simultaneously in USE. This means that the user cannot browse WAP pages and send/receive MMS messages at the same time.
An AP is active when you see the letter G inside a box in the top left corner of the device display. An AP will be activated whenever an application (for example, MMS client or WAP client) requests access to the GPRS network. If there is no traffic for a certain period of time, the connection will be dropped. If the network requests, the connection can also be suspended, for example, for an incoming voice call. The session mode in access point settings defines only the used port number for the WAP connection.