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I am doing an InternetConnect (Wininet) to an FTP server that happens to be running on an iPhone. When the user is on a normal WiFi network it works fine for him. When he has an ad hoc network with his iPhone he gets an ERROR_INTERNET_TIMEOUT. I presume this is some kind of routing problem. I am curious as to why this gets ERROR_INTERNET_TIMEOUT and not ERROR_INTERNET_CANNOT_CONNECT. Most users, if they are blocked by, for example, a firewall, will get ERROR_INTERNET_CANNOT_CONNECT.

I don't understand enough about low-level TCP/IP to understand what kind of situation would cause a timeout error instead of a connect error. I'm really more intellectually curious in understanding this than I am in actually solving the user's problem. ;-) Can anyone explain what is happening with the network packets (the more detailed the better)?

edit: note that, as far as I know, the user doesn't have an outgoing firewall enabled, it's not a firewall issue. I think it's some kind of routing issue. I have seen similar issues when a user is connected a VPN and their routing is set up incorrectly and all packets go to their work instead of the iPhone. I want to know what's going on with the packets in this situation: the socket connects but at the next step (whatever that is) they can't communicate.

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Firewalls these days choose to not respond at all to packets that they deem suspicious, this is to prevent port scanners from detecting that there is a machine at the IP. So that could be what is happening in your case, the firewall may simply be dropping the packet and causing a timeout rather than a failure to connect error.

于 2008-10-01T19:12:27.563 回答