The problem can also happen on the other end of the wire, on the adapter end.
Do you know what the tension for the spring? Would think it requires a good amount of tension to avoid too much angle movement. And what's a good place to get the spring?
Yes, I am connected to the store's wifi. Once I am on their network, how do they actually grab it? What headers names do they inspect for, etc. I'd like to actually know the implementation details and code sample. I looked everywhere on Stackeroverflow and can't find anyone who has done this.
Since you are connected to their network they know your MAC.
What they will likely do is take your IP and look to which MAC their DHCP-Server has assigned that IP to. There are other possibilities though, but they are more complicated (using ARP-cache or requests, doing a raw packet dump at the webserver).
If you want learn more, I think you could read a bit about the different layers first, and then read about how ethernet, IP/ARP and DHCP work. There are likely no "headers" (I assume you mean HTTP-headers) they inspect.
A MAC address is part of their network once you attempt to connect to their wifi. The MAC address identifies your physical network adapter to the router. Once your network adapter is known by the router, the router can assign your adapter an Internet Protocol (IP) address.
Note: the above is a 10,000 foot observation of what happens.
Yes, I am connected to the store's wifi. Can you point me to some code that actually can grab the mac address? As the title suggests -- I want to know how they do it.
What you're asking is, in essence, "how does ethernet work?" That cannot be explained in a few paragraphs. You can start with Richard Stevens' "TCP/IP Illustrated, Vol. 1", as one of many available descriptions. You can use Wireshark to track all of the details.
At this point you should stop asking questions here. There's likely no simple answer, and this is a great chance to experiment and figure it out for yourself.
(Even if someone knows the exact details of how Starbucks does it, you are unlikely to understand the explanation without understanding some of the fundamentals.)
ok, I think I got it. Fundamentals I know enough to be dangerous, thanks for the pointers to captive portal. I'll be able to run with this now... I upvoted you and 0x0
I ran ifconfig en1 | grep ether and the mac address showed up on my URL omnibar when I firebugged it.
I've even noticed this happening at Starbucks whenever you use their WiFi - they will sniff your MAC address and it shows up in the URL omnibar when you agree to the WiFi terms.
Will the real hackers please chime in on how this (grabbing MAC address) can be achieved...
Yes, this happens at Starbucks because your MAC address is captured when you connect to their wifi network (this happens on virtually any captive portal, not hard). I, for one, cannot find my MAC address in a long list of history because it is simply not passed via web requests.
You can get the MAC address of anyone who is connected to the same network - but that's it.
@gonzi I think your comments are a bit cynical. I don't think this sort of stuff is common knowledge. If it is true that there is a ring of sellers, this is really highly coordinated, dare I say almost organized ecommerce crime. I for one, certainly would like to know these sellers get away with it. I think it is appropriate to get Hacker News community to weigh in on how it might be achieved.
This app looks great, but the only negative for me is that it does offer the ability to take a camera snapshot of a real receipt. Some other apps have this receipt snapshot feature, but not the simplicity of your app. For me this snapshot feature alone would complete the perfect app in this category, and for this reason alone I am holding off on the purchase.
