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No TCP over GPRS, UDP only!

Posted on 2004-08-16
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4,004 Views
Last Modified: 2013-11-29
Hi, i have a motorola c350 connected to my laptop via usb cable, it detects it as a modem, i dial up *99# and it connects up fine, however then i cannont use a web brower or anything as i dont seem to have TCP , a can open a UDP connection to the gateway(9201) thats set inside the phone

i get the following settings
description WAN PPP/SLIP INTERFACE
ip address 172.26.48.5
subnet 255.255.255.255
gateway 172.26.48.5
dns        209.212.96.1
             209.212.97.1
netbios over tcp disabled

now if i bring up my nokia 7210 emulator on the laptop and tell it the GPRS gateway is 196.11.240.251, the the emulator can go surf wap sites and all that, retereive jpgs and stuff, that all seems to work over UDP

i'm on MTN south africa
i just don't seem to have TCP
, if I use my VODACOM sim , then it works just fine!
any clues?
i have tried using the proxy 80, 8080, 3128(196.11.240.251), and none can connect! if  i dial up with a fixed line then the proxies above work, its almost like TCP traffic is DENIED for me!

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Question by:bat-man
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Expert Comment

by:Julian_C
ID: 11809605
It's not something I've seen before. When you talk about using your emulator and GW address staring 196, where does that address come from? Not from your GPRS connection? Is it your broadnband GW?

Does your phone have a browser built in and does it connect OK to WAP etc using GPRS? If it does then you need to  run a packet sniffer on your machine as it sets up the connection to your modem and gets dhcp'd etc. Something decebt that can work to quite a low level I'd have thought. If you can run UDP it means your GTP tunnel is OK. I need a bit more detail to go any further with this.

Cheers
Julian
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Author Comment

by:bat-man
ID: 11809729
the GW address is  the one thats on my phone, i'm not putting that in my browser or anything dumb like that, the emulator i have actually uses that UDP gateway, just like the phone would if it was connected on its own. the phone has its own wap browser built in, that works great, i can also use the broswer winwap pro ( freely avaialbe to test wap sites)  it also has the ability to connec to the gateway on port 9201(UDP) it works too. but once again its all UDP.
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Expert Comment

by:Julian_C
ID: 11810152
Sorry to ask the dumb question BTW, you never know whether to ask the bleedin' obvious or not but your content should have given me the clue :-) Also, I've now re-read your question and I see what you are saying. If you connect as a modem you can't browse using a standard browser as TCP seems to be blocked but, if you use the emulator that does it all via UDP then it works fine. This seems to suggest a call to the provider as it does indeed look like TCP is blocked and that the GPRS connection that they provide is only set up to work via the phone using WAP on UDP and they didn't think you might want to spend money with them by surfing the web and POPing your email using your phone as a modem.  :-)  The Vodacom sim swap rules out the phone so it really looks like a call to the provider I'm afraid and I bet the technical support is geared up for that call :-(

It's a very odd thing indeed. Does DNS work from your PC? Can you see the traffic on port 53.

Cheers
Julian_C
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Author Comment

by:bat-man
ID: 11810386
for reasons i cannot say why, i can't phone the techs. there's no traffic on port 53, i wonder if i can set somethign up like this



laptop --- own installed proxy to convert TCP to UDP  <----> celllphone/gprsgateway <--> internet

so i can sort of tunnel through the UDP gateway?
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Expert Comment

by:Julian_C
ID: 11813542
Before we go any further why isn't there any traffic on 53. DNS is a UDP service so if UDP is really working you should see traffic when you resolve names. But nothing? If we prove that UDP works, without question (so we see DNS queries across 53) then we can think about a proxy. What's your programming like? Done any network coding because I've never seen a TCP to UDP converter. It sounds almost out of the question with a true application proxy that keeps the sessions open etc etc.

Cheers
Julian
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Author Comment

by:bat-man
ID: 11818036
yep, i'm a software devloper for a living, done spans of tcp coding, anyway, after playing around with the phone, i found a different APN on the inter, chucked that it, and now i can connect to port 8080 on that IP via TCP, still no dns tho. now the funny thing is that if i then chuck those proxy settings (8080) into IE, it does not work, but if i chuck then into download accelerator, then it does work, however it only works with downloads that have alreayd been added to DAP. IF i add a new file, it just downloads 0kb, and says its done, if i browse to 196.11.240.251:8080 it then gives me simple text saying the password is incorrect! So now i can get to the proxy, via TCP, however I can't get any further, still can't get and DNS! and it seems the address 196.11.240.251:8080  only works from when  u dial in via GPRS, if u use normal dial up, then it doesnt seem to exist!
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Accepted Solution

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Julian_C earned 250 total points
ID: 11820200
Have you thought about it all being down to DNS? Download accelerator may work with previously added items as it could resolve the names to ip's and that's how it stores incompete downloads. Where's it keep these items? Run filemon and regmon against it to see where it picks up these old items. Have you tried adding a download by IP only, or even using the IE proxy and going to an address by IP not by name. A known site you won't have in your cache (just in case!) is http://213.232.92.76


The fact that you can't get DNS, a standard UDP service suggests it's not just a UDP works, TCP doesn't problem, especially when you add the rest of the anomalies.

Finally, as a programmer with lots of sockets experience you'll know that converting TCP to UDP and back again will require a major app proxy. Could be fun tho :-)

Cheers
Julian
0
 

Author Comment

by:bat-man
ID: 11820476
well i can't ping any addresses, i've done a scan , that doesnt work either! but i found an old program i had ccproxy, installed that, set it up as a cascading proxy to the gprs gateway,set IE to use the ccproxy and then things start to work, i can download at about 5k with DAP, IE is a bit slow but it works, funny thing with CCPROXY is you can also put port forwarding in it, which i tried, for my mail server, and somehow it can find pop.mighty.co.za and forward my pop traffic to it, so i can even get my email, i'm still not sure how CCPROXY is getting to the external ip's but it is, and its cool, now if only i can get MSN to work!
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Expert Comment

by:Julian_C
ID: 11821521
That's very odd. Sounds like it's not able to maintain a TCP session. Packet sniffer?

Cheers
Julian
0
 

Author Comment

by:bat-man
ID: 11829857
it seems that for some reason some applications cannot pick up the TCP connection, cause my IE won't work on the same PC as the proxy, however OPERA does, IE running on a different pc to the proxy pc does work though! Yahoo IM works, MSN messenger doesn't , my port scanner Does pick up port though.
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