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Can you say how to website can can obtain real IP user with JavaScript, whereas people using a proxy, please?

Thanks

pnuts
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lenine
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  • You still need to have some server side code (or use other site for IP) like: http://stackoverflow.com/questions/17414972/get-ip-address-with-javascript – Jason Lou Nov 16 '15 at 23:18
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    You can only obtain request IP address, which is external one. – MaxZoom Nov 16 '15 at 23:19

2 Answers2

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Client-side Javascript cannot, by itself, obtain your IP address. And, even if it did, what it would likely see is an internal network IP address, not a public IP address.

So, the only way to get the IP address from plain Javascript is to ask a server to tell you what your IP address is. You make an Ajax request to the server with a request that tells the server you want it to return what your IP address is. The server can then return the IP address that it sees your connection coming from. This address will be your outwards-facing public IP address. Since most client computers these days are behind some sort of router/firewall, what the server is probably seeing is a single public IP address that is being NATed from your actual client computer.

If there was a proxy server in the route between my client computer and the server, then the server would see the IP address of the proxy server, not the IP address of the client computer. And, there is nothing you can do to change that. Proxies and routers are specific designed to map one set of private IP addressing to a public IP addresses while keeping the network topology of the private network completely hidden from the outside world.

For example, the actual IP address of my local computer right now is 192.168.1.17 which is a local IP address on my home network. But, when I ask a server out on the internet what my IP address is using a service like http://whatismyipaddress.com/, then it reports the actual public IP address that Comcast has assigned to my router which is 67.180.86.xxx. When I make a connection to the internet from my local computer, that connection goes first to the router where the router uses NAT (network address translation) to map this connection between my private IP address on the home network and a particular outgoing TCP connection from my public IP address. When packets flow back on that connection, the router forwards those packets to my private IP address on the home network.

jfriend00
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  • I know that it is possible. Tor broswer, block JavaScrip beacause they can obtain real public IP address of client. And I would know how to JavaScript can obtain ,the real public IP adress, whereas user use a proxy server. – lenine Nov 17 '15 at 15:43
  • @lenine - As I said, the only way to obtain your public IP is to ask a server. – jfriend00 Nov 17 '15 at 20:27
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I know that it is possible. Tor broswer, block JavaScrip beacause they can obtain real public IP address of client. And I would know how to JavaScript can obtain ,the real public IP adress, whereas user use a proxy server.

lenine
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