Dear Wayne, Thanks so much for your email!
I don't understand your opinions well. Jens said 3G did not allow incoming connections. So I think P2P does not work in such an environment. I have to try to use app notifications. The major reason I use P2P is to get a lower load on the server and users can get pushed data. For iPad/iPhone within a NAT, I will ask the device to connect the server outside the NAT firstly. So a connection can be established. Pushing can be done without the block of NAT. Do you think my solution works? Best, Bing On 2011-8-23, at 上午12:48, Wayne J wrote: > The issue is more general than 3g vs wifi. There are several issues involved > here neither of which or 3g specific. > > There are generally firewalls between the Internet and intranets. For > security reasons, incoming connections are not allows for non-server > machines. > > It is very common for intranets to use non-routable IP addresses internally > and connect to the Internet via NAT (network address translation.) This > servers tow purposes. It allows an intranet to share IP addresses with many > machines. There is also a secondary benefit. Because of the way NAT works, > unless you explicitly setup rules for incoming connections they cannot be > routed. The router implementing the NAT is directly addressable from the > Internet but machine inside the Intranet are not addressable from the > Internet. > > You want this for you iPhone and your iPad. > > * It makes it harder to exploit your phone from the Internet. As is it you > (the user) must connect to some Web service in order for exploits to be taken > advantage of. > > * You don't have random computers trying to connect to your device all the > time. There are many people all over the world who are constantly running > scripts that scan blocks of IP addresses for known exploits. If you device > where directly accessible you would end up paying for the data sent to your > phone during these attempts. The amount of data is small but the attempts are > fairly constant. > > * Your device cannot be specifically targeted with a DOS attack. This will be > even more important as we move into the new wireless technologies. The new > technologies are moving towards some form of VOIP for calling. A DOS attack > could prevent you from even making a call (say to 911.) > > I don't believe there are any technical reason why you could not setup a 3g > network where phones could communicate in P2P mode or even run some sort of > server. > > > Wayne > > > On Aug 21, 2011, at 11:19 PM, Bing Li wrote: > >> Dear Jens, >> >> I just know about the constrains on 3G. Thanks so much for your replies! >> >> I will implement my system on WiFi first. Because of LAN, the multicast is >> not so flexible as on a true P2P. The load on my server must be high. >> >> On 3G, the iPad must always establish the connection and send requests >> before getting data from other nodes, right? That is not my expectation. I >> will try app notifications instead. >> >> Thanks again! >> >> Best, >> Bing >> >> >> On Mon, Aug 22, 2011 at 1:49 PM, Jens Alfke <j...@mooseyard.com> wrote: >> >>> >>> On Aug 21, 2011, at 10:32 PM, Bing Li wrote: >>> >>> According to your email, P2P is not available on 3G? >>> >>> >>> A device can’t receive an incoming TCP connection over 3G. That’s part of >>> the way the carriers run IP over their cell networks, not anything mandated >>> by Apple. >>> >>> (All the incoming signaling handled by iOS, like phone calls, SMS, and app >>> notifications, runs directly over GSM without using IP. 3rd party apps >>> definitely don’t have access to that low-level functionality; the carriers >>> are pretty nervous about unauthorized use of it.) >>> >>> If so, P2P based applications cannot be launched in AppStore? >>> >>> >>> No, it doesn’t rule out P2P, it’s just that the device will have to be the >>> one making the connection. >>> >>> For example, it’s possible to run a BitTorrent node without accepting >>> incoming connections; in practice, the other nodes will think you’re >>> leeching and probably won’t send you much data, but that’s a matter of >>> configuration, not part of the protocol. It all depends on how your protocol >>> works. >>> >>> Without 3G's support, how can a P2P system run in a wireless environment? >>> >>> >>> WiFi? Bluetooth? >>> >>> >> >>> —Jens >>> >> _______________________________________________ >> >> Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) >> >> Please do not post admin requests or moderator comments to the list. >> Contact the moderators at cocoa-dev-admins(at)lists.apple.com >> >> Help/Unsubscribe/Update your Subscription: >> http://lists.apple.com/mailman/options/cocoa-dev/lwj.groups%40gmail.com >> >> This email sent to lwj.gro...@gmail.com > _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
