whatsapp technology

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Richardhb

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Can anybody post a link to a decent simple article on how whatsapp actually "talks"to the correct cellphone or give a simple explanation.

At one stage, according to some literature, it used the imei number of the cellphone to send messages to a device. Now whatsapp claims to have dropped that and use the cell number.

However, if I remove my sim card from my phone it is still able to use my wifi connection for messages. I can also put in a different sim card and it carries on working. So it looks as though after the initial registration the sim card, apart from providing a data connection if necessary, isn't actually required.

It looked as though it was able to use the MAC address for a device but I don't know if every cellphone would have one.

So I really would like to know by what it recognises the cellphone to send messages.
 
Whatsapp is not tied to the SIM or a phone number. You can install Whatsapp on any phone, any SIM card, even without SIM card. The phone number is just a form of your login name.

There is many ways Whatsapp can identify your device and I see no reason why you should know anything more about this... Seriously.
 
Cellphone number used as identifier to confirm the WhatsApp profile. Once logged in, you're probably assigned a username/password combo that is unique to your device and you basically never log off.
You use that to "call" the WhatsApp server and send/receive those messages.
 
Richardhb said:
Can anybody post a link to a decent simple article on how whatsapp actually "talks"to the correct cellphone or give a simple explanation.
Click to expand...

Whatsapp makes use of your address book then checks to see which of those numbers are verified with WhatsApp itself.
More information here
 
WAslayer said:
People learn through curiosity and this is what has gotten society to the modern age we are at now..

Let the guy learn if he wants to learn. What harm is it to you for him to know more about how WhatsApp functions..
Click to expand...
THIS.
ffs.
 
Richardhb said:
Can anybody post a link to a decent simple article on how whatsapp actually "talks"to the correct cellphone or give a simple explanation.

At one stage, according to some literature, it used the imei number of the cellphone to send messages to a device. Now whatsapp claims to have dropped that and use the cell number.

However, if I remove my sim card from my phone it is still able to use my wifi connection for messages. I can also put in a different sim card and it carries on working. So it looks as though after the initial registration the sim card, apart from providing a data connection if necessary, isn't actually required.

It looked as though it was able to use the MAC address for a device but I don't know if every cellphone would have one.

So I really would like to know by what it recognises the cellphone to send messages.
Click to expand...

I haven't been on WhatsApp for a while, but used it extensively on non-supported device using third-party app. Simple answer to your main question:

WhatsApp does not 'talk to the correct cellphone' ... it just talks to the last cellphone used/registered. In other words, WhatsApp can only be used on one device at a time. As soon as you register the account on another device, it gets deactivated on the previous one.

No MAC addresses/IMEI/etc. involved, as you've already found out. As for knowing if 'this' was the last device communicated with, my understanding has been that there's a token passed between the device and server (which also helps the server/device to 'know' which messages were last received by the device). This token is the 'thing' WhatsApp uses to know they're talking to the correct cellphone. Any other cellphone, which doesn't know that last token, will prompt a re-registration.

I might be wrong/mistaken and/or use incorrect terminology, but I believe that's how it works.

You can look at the code of third party whatsapp applications, e.g. yowsup to understand it better
 
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The above sounds like something close to how it is likely to work..

The token, taking an educated guess, is probably a signed token consisting of phone specific details IMEI as an example as well as the phone number, to ensure no duplicate tokens exist..
 
WAslayer. I've been thinking about your reply and I think that must be about as close as I'm going to get an answer to my question. I've come across a situation similar to whatsapp with Filimin lamps which I have one of and my daughter in New Zealand has a similar one. They also "communicate" with each other with a fairly exotic method. Which apart from knowing your lamps serial number (cellphone number) you don't need any further details. They even setup the internet connection without you needing to tell them the password of your router. So you are probably close to the nub of the matter that whatsapp uses a token unique to each user's phone which gets accessed on a central server via the cellphone number stored in a database. So the Sim card, apart from the initial setting up, doesn't actually have to be in the phone for whatsapp to function.
 
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You don't even need SIM card to be in the smartphone on 'initial setup' - the SIM card can be on a feature phone for example. As long as it can receive the SMS, you're good to go
 
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