How to distinguish one mobile device from another by HTTP request

I have a web application that is accessed from mobile devices. I need to detect that some requests are made from one device while others from another. I don't necessarily need to know the unique devic开发者_Python百科e id or something like that, I just need to distinguish one device from another. I thought about using IP address, but I'm afraid that some carriers might have similar IPs for all devices in some region. Is there a common way of doing this? Thanks!

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That's usually done with cookies with unique identifiers (session ID for example)

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Yes, normaly wap gateways has few IP in each region. You can use cookies although it could cause some problems because many wap gateways doesn´t support. So you can use URL session ID.

Some carriers include in HTTP headers unique ID (some info). You should investigate this option too.