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Who's afraid of GPRS ? (GPRS for the uninitiated)
May 25, 2004
With all the hype of 3G most people have heard about GPRS. Without delving into the world of GSM and telecoms - GPRS is just another transport. As far as the Application Programmer is concerned, once a GRPS connection is in place a mobile device is in effect connected to the net, it has an IP address and can open and accept socket connections. Obviously the same restrictions related to firewalls apply equally to mobile devices as they do to desktop clients. Another restriction which may apply is the Access Point Node or APN. An APN is the GPRS equivalent of a firewall or proxy which can limit or restrict the type of traffic that can be sent over a GPRS channel.
Most network operators also have an "open" APN which allows unrestricted traffic. Another feature of GPRS which can be problematic is the fact that mobile devices normally get a dynamically assigned IP address (i.e. DHCP). While this may be efficient for the network operator it can play havoc for Application Programmers as it may be impossible to accurately determine the mobile device's IP address. Due to the possibility of losing signal within GSM networks, there is the added headache that the IP address can also change unexpectedly. As long as the mobile device initiate connections (and reconnections) this should not cause problems however.
Finally some network operators often favour voice channels over data channels so be warned that you may have problems getting a GPRS connection in heavily loaded cells in the first place.
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