Thread: [Android] CC won't connect to Calibre
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Old 12-30-2016, 03:45 AM   #4
chaley
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Posts: 12,476
Karma: 8025702
Join Date: Jan 2010
Location: Notts, England
Device: Kobo Libra 2
Quote:
Originally Posted by Wryhder View Post
Thanks, Chaley.

I just got back home from school and downloaded CC to my sister's android phone.
It connected successfully, no tweaking required.
I tried to connect mine immediately afterward, and for the first time in months it did connect.

I tried a second time to be sure it wasn't a fluke. It connected.
Then my pc's wifi temporarily disconnected, and the problem started all over again. Until I connected my sister's phone. I could then connect again. I wonder why that is.
Are the two phones configured in exactly the same way to connect to calibre? IIRC your phone uses a fixed IP address.

Do the two phones use the same WiFi band? One might use 2.4 ghz and the other 5 ghz. If so then the router might behave differently.

What I am thinking is that there are some issues during the process of mapping an IP address to a device, and that some difference between how your sister's and your phones are connected is triggering these "issues".

The way connecting works is:
  • Every device on a network has an unchangeable (usually) physical address called the MAC (Media Access Control) address. The MAC address must be known in order to exchange network packets with a device.
  • When starting a connection, an "app" tells the OS that it wants to connect to an IP address.
  • The OS looks to see if it already knows which MAC address belongs to that IP address. Assume that it does not.
  • The OS does a "broadcast", asking all devices out there whether they have IP address X.
  • All intermediate devices (routers, hubs, etc) must relay the broadcast.
  • If a device does have that address then it replies to the broadcast sender with its MAC address. Again, all intermediate devices must relay the response.
  • The first OS puts the address into a local table so that it doesn't need to ask again.
My feeling is that your sister's phone's connection is somehow causing some intermediate device (e.g., your dongle, a router, the calibre machine) to get the correct MAC for an IP address so it doesn't need to ask later. It isn't at all obvious to me how this should happen except in the presence of "strange behavior" in one of the devices, but it does seem that some kind of pump priming is happening.
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