How to get the MAC address of the visitors' PC in an ASP.NET webApp?

Question

In an ASP.NET (C#) WebApp, I can get the IP of the visitors' PC easily, But How to get the MAC address of the visitors' PC in an ASP.NET webApp?

And this ASP.NET app is runing on the inner intranet of our company, and the visitors are also in the same inner intranet of our company.

Answer 1

The MAC address is not part of the IP header (or any other protocols above that), and thus not available if all you see is the HTTP traffic.

EDIT (after OP's update): Since clients and servers are on the same internal network, wouldn't it be better to get a host name from the IP address instead of the MAC address? You can easily look up the host name based on the IP address.

Answer 2

The answer that immediately comes to mind, is that this is only possible if you write an ActiveX control that runs in the client browser to obtain this information on your behalf. On the other hand it might be possible with JavaScript on the client if the javascript can instantiate a COM object that will get the information. The only other way I can think of is have a windows service that does an ARP request once the IP has been captured.

Answer 3

You can't easily do this. There are protocols such as ARP which allow translation between MAC and IP addresses, but this traffic is typically behind a firewall and so not available to you on a public website.

On an intranet, you might be able to do something, but not via ASP.NET. You would need to use other mechanisms to capture this information - but those kinds of tools (e.g. packet sniffers) are generally not available to developers and may contravene corporate IS policies.

Answer 4

Since you're on the same subnet, you can P/Invoke GetIpNetTable to get the webserver's ARP table. If you do this real-time, no additional work would be necessary - since you're having a conversation with the client, you'll have the ARP info. Otherwise, you'd need to construct an ARP request or some IP traffic (say, a ping) to get it in the cache - and note that due to DHCP and other network vagaries (like a machine being turned off), it is possible that converting IP to MAC later will yield a different answer.

Note also that any external clients (ie., ones across a router) just won't show up in the table - so be prepared to deal with that as well. If you need a MAC for them for some reason, it's technically your router's MAC.