NFC(Near Field Communication): Android to Android

Near field communication (NFC) is a set of ideas and technology that enables smartphones and other devices to establish radio communication with each other by touching the devices together or bringing them into proximity to a distance of typically 10 cm (3.9 in) or less.

RFID is the process by which items are uniquely identified using radio waves, and NFC is a specialized subset within the family of RFID technology. Specifically, NFC is a branch of High-Frequency (HF) RFID, and both operate at the 13.56 MHz frequency. Evolved from radio frequency identification (RFID) tech, an NFC chip operates as one part of a wireless link. Once it's activated by another chip, small amounts of data between the two devices can be transferred when held a few centimeters from each other. 

NFC is designed to be a secure form of data exchange, and an NFC device is capable of being both an NFC reader and an NFC tag. This unique feature allows NFC devices to communicate peer-to-peer. At the end of the day, NFC builds upon the standards of HF RFID and turns the limitations of its operating frequency into a unique feature of near-field communication.

The HCE(Host-based Card Emulation) architecture in Android is based around Android Service components (known as "HCE services"). One of the key advantages of a service is that it can run in the background without any user interface. This is a natural fit for many HCE applications like loyalty or transit cards, with which the user shouldn't need to launch the app to use it. The whole idea behind using a service as the target for HCE events (and not an activity as it is the case for other NFC events) is that the HCE functionbality should be accessible at any time and does not require an activity to be in the foreground.

NFC does not work if screen is BLACKED out. NFC may not work if the screen is UNLOCKED. NFC will work when is screen is LOCKED. That’s when HCE Service on the device wakes up. processCommandApdu() is called whenever a NFC reader sends an Application Protocol Data Unit (APDU) to your service. APDUs are defined in the ISO/IEC 7816-4 specification as well. APDUs are the application-level packets being exchanged between the NFC reader and your HCE service. That application-level protocol is half-duplex: the NFC reader will send you a command APDU, and it will wait for you to send a response APDU in return.

public class MyHostApduService extends HostApduService {

    @Override

    public byte[] processCommandApdu(byte[] apdu, Bundle extras) {

       ...

    }

    @Override

    public void onDeactivated(int reason) {

       ...

    }

}

ref:

NFC - http://www.nearfieldcommunication.org/

Emulate a NFC tag with HCE to open a door with a NFC/RFID lock - http://www.reddit.com/r/androiddev/comments/2vfb1e/emulate_a_nfc_tag_with_hce_to_open_a_door_with_a/

NFC HCE -  https://developer.android.com/guide/topics/connectivity/nfc/hce.html#HceServices

NFC vs RFID - http://blog.atlasrfidstore.com/rfid-vs-nfc

Tech Tips ..

1. Check whether remote machine is Virtual machine or Physical machine

Virtual Machine => dmidecode  | grep -i "vm"
Physical Machine => dmidecode | grep -i vm

example:

Virtual Machine:
[root@localhost ~]# dmidecode  | grep -i "vm"
        Manufacturer: VMware, Inc.
        Product Name: VMware Virtual Platform
        Serial Number: VMware-56 4d d6 6c 32 aa e1 46-46 8b e8 da 78 cb 78 ef
               VME (Virtual mode extension)
        Description: VMware SVGA II
        String 1: [MS_VM_CERT/SHA1/27d66596a61c48dd3dc7216fd715126e33f59ae7]

Physical Machine:
dmidecode | grep -i vm
        VME (Virtual mode extension)

2. Resolve VNC Client DISPLAY blank issue

This issue may be due to corruption of VNC Server xstartup file. SSH to your VNC Server machine and remove/move the ~/.vnc/xstartup file


3. Shift between Android and Linux Distro on Android Device using chroot

It looks like we can install any Linux Distro(Debian, Ubuntu ..) on Android device as both share the same kernel. We can shift between Android & Linux Distro on the android device using chroot(which is used to shift between different root file systems). As we are completely shifting the root file system, all linux commands/exes should run on Android device too ..

I found the below resources online. They may be useful:

How to install Ubuntu on Android -

• http://androlinux.com/android-ubuntu-development/how-to-install-ubuntu-on-android/
• http://nexusonehacks.net/nexus-one-hacks/how-to-install-ubuntu-on-your-nexus-oneandroid/

chroot command : A chroot on Unix operating systems is an operation that changes the apparent root directory for the current running process and its children. A program that is run in such a modified environment cannot name (and therefore normally not access) files outside the designated directory tree. The term "chroot" may refer to the chroot(2)system call or the chroot(8) wrapper program. The modified environment is called a "chroot jail".

ref:

http://www.linuxquestions.org/questions/linux-server-73/how-to-know-the-remote-machine-is-virtual-machine-or-physical-machine-913526/