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I've recently bought a UMTS surf stick from German ISP and cell phone carrier 1&1. I'd like to host games (Settlers) that require a direct connection to other players via TCP/IP.

I understand that if I were connecting to the internet via router I'd have to forward incoming connections on the appropriate ports directly to the computer that is hosting the game. I'm not familiar enough with my connection here, though, to figure out how to do port forwarding. Other players can't connect to my laptop via my IP (no, firewalls are not the issue).

Anyone got an idea? A 1&1 service representative said that they don't block any ports.

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up vote 3 down vote accepted

It sounds like what the actually issue is is that your phone carrier has you behind a router.

It might make more sense like this:

[Internet] <---> [ISP's NAT] <---> [Your laptop]

So what's actually occurring is that you do not have an IP address that actually faces the internet. Your ISP is using Network Address Translation to make a small selection of IP addresses available to a larger number using cell phones/air cards.

What you may be able to do to get around this is to use something like Hamachi or Remobo. Think about them as a peer-to-peer VPN. To applications, it will look like you are all on the same LAN, regardless of what your connection is.

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Thanks. Yes, I figured that the carrier is sitting behind a router. The lady on the phone didn't understand my question so naturally I doubted her answer. Glad to hear that my initial assumption was right. I'm trying Hamachi right now and will report back whether it works and if that resolved the issue. – Jan Kuboschek Jul 17 '10 at 22:48
worked perfectly. thank you! – Jan Kuboschek Jul 18 '10 at 13:53

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