FabM85
Posts: 1
Joined: Thu Jun 01, 2017 1:37 pm

3G Modem for inbound connection

Thu Jun 01, 2017 1:54 pm

Hello,

I'm working on a project in which I need a inbound connection via "3G usb dongle" to my Raspberry Pi. I tried the E173 and for outbound connections works fine, but not for inbound connections (in windows this works).

Does anyone has experiance with this problem? And can advice a 3G dongle that works with inbound connections?

Some of the dongles that are available where I live are E303, E1553, E3531, please let us also know if other types of modems have this functionality.

Thanks

User avatar
topguy
Posts: 4427
Joined: Tue Oct 09, 2012 11:46 am
Location: Trondheim, Norway

Re: 3G Modem for inbound connection

Sat Jun 03, 2017 5:02 pm

Be more specific with what you mean as "inbound connection". Do you mean an incoming TCP/IP connection ?
Normally I would say that the inability to receive socket connection with 3G modems is caused by the GSM provider. There is not enough IPv4 addresses for all mobile phones to get their own address so they use NAT'ing to give you a private IP-address. And since you dont have access to "the router" you can do port-forwarding the way you would on your home internet.

If it works on Windows then the module is probably Ok, I would say this is a network setup issue not a hardware issue.
Then the more interesting questions becomes what is different in the windows setup and the Raspberry setup ?
- Different SIM card ? different APN ?
- Support for IPv6 on Windows, but not on Linux. ( There are many more IPv6 adresses so each device can get its own )
- How do you test/use incoming connection on Windows ? Do you find the ip-adress (and if that is the case what kind of ip do you get ) or use some Dynamic DNS service ?

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