Thursday, December 22, 2011

NFC - NDEF Support

NDEF messages are the standard way to write information to NFC tags on Android.
The latest version of PAW (0.84) has support for text, URI, smart poster and mime media NDEF messages.
The classes and their methods are described in the PAW Functions documentation within the PAW web application.
NFC support is now also available in PAW Runtime.
To show how the new functionality can be used (and to give you the possibility to play with NFC tags), a NFC reader/writer plugin is available for PAW. This plugin is also available in the newest add-on package for PAW Runtime.

Here are some screenshots...


NFC Plugin
Plugin requesting NFC Tag


PAW Runtime with NFC Reader/Writer
Runtime version

This will be the last update of PAW this year and possibly the last blog entry.
To all of you ... Merry Christmas and a Happy New Year :)

Thursday, December 15, 2011

ICS: Getting NFC Tags to Work

Since December I'm a happy owner of a Galaxy Nexus :)
NFC seemed like an interesting thing, so I started to integrate NFC support into PAW.

First thing I did was to order some Mifare Classic 1K tags from
They arrived fairly quickly and delivery was free of charge.
NFC Tags
To try things out I installed a lot of NFC reader and writer apps. To my dismay none of them seemed to work.
They could read the tags but could not write them. Having no idea how NFC worked, I was fairly disappointed :(

Searching the web I found out that this seems to be a bug in ICS:

Googles sais that there will be a fix provided, but when, no one can tell.
So I tried to get it working myself...

If you would like to test the things below, install the latest PAW version (0.80) from the Android Market.

This solution is only working for Mifare Classic 1K tags!
If you try as described you do it at your own risk!
It's not my fault if your tags do not work afterwards!

Read the updates at the end of the post first!
This solution is no longer necessary and will most likely damage your tag(s), so do not use it!

The Problem
The problem (as reported in the bug report) seems to be that the tech reported by the tag do not contain which is necessary to write NDEF messages.

You can try this with the following code that you can insert into the BenShell Console of the PAW web application:

import android.nfc.NfcAdapter;

intent = AndroidInterface.getNfcIntent(5); // 5 secs timeout
if(intent != null) {
  tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
else {
  print("No Tag found!");

If the result is TAG: Tech [,] writing NDEF messages will not work!

The Possible Fix
As mentioned above I have no expirience with NFC, so I tried to find a solution that worked without having to know NFC or the Mifare tags in detail.

I searched the web and found some Mifare Classic 1K dumps at the nfc-tools site.
After downloading a dump I tried to write it to the tag. Interesting enough it seemd to work :)

After writing the dump, the above script reported:
TAG: Tech [,,]

So here are the step by step instructions:
  1. Download the dump file from the nfc-tools site: mfc_1k__url_nfc-tools.mfd
  2. Save the dump file to the /sdcard of your android device.
  3. Start PAW and open the BeanShell console.
  4. Copy/paste the following script into the console:
    Mifare Classic - Write dump
    import android.nfc.NfcAdapter;
    import android.nfc.NdefRecord;
    import android.nfc.NdefMessage;
    import android.os.Bundle;
    intent = AndroidInterface.getNfcIntent(5); // 5 secs timeout
    if(intent != null) {
      tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
      if(tag != null) {
          nfc = MifareClassic.get(tag);
        print("Is connected: " + nfc.isConnected());
         fis = new FileInputStream("/sdcard/mfc_1k__url_nfc-tools.mfd");
         b = new byte[16];
         errors = 0;
        sectors = nfc.getSectorCount();
        blocksPerSector = nfc.getBlockCountInSector(0);
        for(sector=0; sector<sectors; sector++) {
          print("Sector " + sector);
          for(block=0; block < blocksPerSector; block++) {
            logicBlock = nfc.sectorToBlock(sector) + block;
            $$.print("  Block: " + block + " ... ");
            if(sector == 0 && block == 0) {
               print("Manufacturer block ... skipped");
            try {
              nfc.authenticateSectorWithKeyA(sector, MifareClassic.KEY_DEFAULT);
              nfc.writeBlock(logicBlock, b);
            catch(e) {
          print("Errors: " + errors);
          print("Dump written!");
       else {
          print("Tag not supported!");
    else {
      print("No Tag found!");
  5. Start the script and as soon as the PAW app is in foreground, place the tag at the back of the phone and leaf it there until the script is finished.
After that the tag is hopefully working.

Good luck and happy hacking :)

Ndef.getMaxSize() returns only 92 bytes that can be written to a NDEF message. I don't think that's normal :(

You can check this yourself with the following code:
import android.nfc.NfcAdapter;
intent = AndroidInterface.getNfcIntent(5); // 5 secs timeout
if(intent != null) {
  tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
  print("Max NDEF message size: " + Ndef.get(tag).getMaxSize() + " bytes");
else {
  print("No Tag found!");

Update 2:
The latest NFC TagWriter by NXP is able to format unformatted tags and fixes the problem.
Here is the Android Market link: NFC TagWriter by NXP

Thursday, December 1, 2011

PirateBox on Android

A while ago psundegroud created the thread [TUT]Roll Your Own PirateBox! PirateBoxMobile. At that time my only rooted device was an old Samsung Galaxy I7500 running Android 1.6. We managed to get this working. The two main issues were that WiFi Tether was needed, which didn't run on all Android devices and that only Ad-Hoc mode was available. The missing Infrastructure mode prevented most Androids from seeing the PirateBox hotspot.

Note: This post is somewhat outdated. The current state of the PirateBox can be found here: PirateBox Reloaded

Meanwhile I have a rooted Notion Ink Adam running AdamComb v0.3. So I tried to get PirateBox running by using the built in tether app. Built in tethering uses Infrastructure mode, which solves above mentioned problem.

On my Adam this is really working fine and I hope that it will also run on other Android units.
I'll divide the post in two parts. The first part describes the technical details, so if someone has problems in getting this to work this might be helpful for further testing.

Along with setting up the scripts I have also written a plugin for PAW which should make setup really easy.
If you are not interested in the technical details you can right jump to the Installing the Plugin section.

Techical Details

Setting up the PirateBox during boot is done by PAW startup scripts.

The main tasks of these scripts are:
  • Killing dnsmasq and restarting it with changed parameters, so that DNS requests always respond with the IP of the Android device.
  • Configuring iptables so that requests to port 80 are redirected to the port PAW is listening on, because PAW can not operate on privileged ports.
  • Change the PAW configuration to use the PirateBox Handler, which ensures that all unknown request are forwarded to the base URL (

The startup scripts are located in the subfolders 0 and 1 of the directory /sdcard/paw/etc/init. These folders represent PAW runlevels. Runlevel 0 is before the server starts and after server shutdown and 1 is after server start and before the server shuts down. Scripts beginning with S_ will be called on startup and scripts starting with K_ will be run at shutdown.

So here is a short summary what these scripts are doing.

  • Checks if tethering is running. If not none of the steps below will be performed.
  • Kills the "original" dnsmasq process and starts a new one.
  • Executes iptables commands to get port redirection working.
  • Replaces the original PAW configuration with the PirateBox configuration.

  • Checks if tethering is running. If not none of the steps below will be performed.
  • Restores the original PAW configuration.
  • Displays a PirateBox notification.
  • Sets the max upload limit to 200MB.

  • Clears the PirateBox notification.
  • Kills dnsmasq process.
  • Stops tetherig and restarts WiFi.

  • Removes iptables rules for port redirection.

If you run into problems have a look at these scripts and try to run the commands inside the scripts individually.

Installing the Plugin

PAW Plug-in Menu
Installing the plugin is easy. I've put it on the PAW plugin page, so you'll find it within the PAW web application or you can direct download it from the PAW Plugin Page.
After download extract the ZIP file to the /sdcard/paw/html/app/plugins directory of your Android device.
Now after re-entering the PAW web application, the PirateBox plugin should be visible in the Plugins menu.

If the plugin setup screen shows a warning in red, the installation is likely to fail, because some prerequisites are missing.
If no warnings are displayed, press the Install button. You can also try to setup a PirateBox Access Point (AP) automatically. I'm not sure, if this is working on all devices. If it's not working, please create an AP manually.
To uninstall the plugin, press the Uninstall button.

PirateBox Plugin

It is important to note, that PirateBox will only be started if tethering is active before PAW starts up.
Otherwise the normal PAW configuration will be applied. So you can choose between these two configurations.

I hope that's not just working on my Adam but on many other devices as well.

Here are some screenshots from my setup...

PirateBox Startup

Connected to PirateBox

PirateBox on Nexus One
PirateBox in Chromium


Here is a video that shows the PirateBox in action...


Since version 0.3 of the plugin, PirateBox is also working on rooted Galaxy Nexus devices running Ice Cream Sandwich.
Here is a video...