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POCreate an access point with the Nexus 7
 

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  1. POCreate an access point with the Nexus 7
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    <h2>What's the aim?</h2> <p>Create an Access Point with an Android device (Nexus 7 in my case). The final purpose is to connect a WiFly card to this created network and exchange data between these devices. </p> <h2>Hardware:</h2> <ul> <li>Nexus 7 with the Android version 4.2.2 <strong>rooted</strong> with the ROM CyanogenMod 10.1</li> <li>WiFly card: Arduino shield with the same layout as Zigbee cards that use Wifi (<a href="https://www.sparkfun.com/products/10822" rel="nofollow noreferrer">the product</a>)</li> </ul> <h2>Software:</h2> <p>I understood that the Android version 4.2.2 does not allow to create an Access Point (the service is disabled programmatically). This is why I rooted my device with the ROM from CyanogenMod. This ROM enable this service. </p> <p>Google has hidden some methods from the class <code>WifiManager</code>. Specifically, the method <code>setWifiApEnabled</code>. This is why I use reflection to call methods on the code below.</p> <p><em>The source code is massive!</em> Focus on the method <code>createAccessPoint()</code>. I chose to put the whole source code to help people that want to know how I did all of this. </p> <pre class="lang-java prettyprint-override"><code>public class TestAccessPoint extends Activity { static final String TAG = "AP_TEST"; static final String SSID = "\"Awesome Access Point\""; static final String PSK = "\"helloworld\""; String numberOfClientsConnected; String wifiApEnable; String wifiApState; WifiConfiguration wifiApConfig; WifiManager wifiManager; WifiConfiguration wifiConfiguration; BroadcastReceiver receiver; BroadcastReceiver receiverWifiDisabled; TextView textView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.accesspoint_test); textView = (TextView) findViewById(R.id.textView); wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE); wifiConfiguration = new WifiConfiguration(); if(wifiManager.isWifiEnabled()) { createAccessPoint(); } else { Log.d(TAG, "Set wifi Enable"); wifiManager.setWifiEnabled(true); receiverWifiDisabled = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { int wifiState = intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE, WifiManager.WIFI_STATE_UNKNOWN); if ( wifiState == WifiManager.WIFI_STATE_ENABLED ) { Log.d(TAG, "Wifi enable"); createAccessPoint(); } } }; registerReceiver(receiverWifiDisabled, new IntentFilter(WifiManager.WIFI_STATE_CHANGED_ACTION)); } final Handler mHandler = new Handler() { public void handleMessage(Message msg) { switch (msg.what) { case 1: textView.setText( wifiApEnable + "\n" + wifiApState + "\n" + "Nb of clients connected: " + numberOfClientsConnected + "\n" + "Wifi AP configuration: " + "\n" + wifiApConfig.toString() + "\n" + "WifiManager connection info: " + "\n" + wifiManager.getConnectionInfo().toString() + "DHCP state: " + wifiManager.getDhcpInfo().toString() ); break; } } }; Thread thread = new Thread(new Runnable() { boolean alive = true; @Override public void run() { while(alive) { try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } numberOfClientsConnected = numberOfClientsConnected(); wifiApEnable = isWifiApEnabled(); wifiApState = getWifiApState(); wifiApConfig = getWifiApConfiguration(); mHandler.sendMessage(mHandler.obtainMessage(1)); } } }); thread.start(); } @Override public void onDestroy() { super.onDestroy(); if(receiver != null) { unregisterReceiver(receiver); } if(receiverWifiDisabled != null) { unregisterReceiver(receiverWifiDisabled); } } protected void createAccessPoint() { // Check if the Wifi configuration already exists List&lt;WifiConfiguration&gt; list = wifiManager.getConfiguredNetworks(); int networkID = -1; if(list != null){ for(WifiConfiguration conf : list) { Log.d(TAG, "Network ID: " + String.valueOf(conf.networkId) + " ; Network SSID: " + conf.SSID); if(conf.SSID.equals(SSID)) { Log.d(TAG, "SSID found"); networkID = conf.networkId; wifiConfiguration = conf; break; } } } else Log.d(TAG, "List of WifiConfiguration is null"); // If the configuration exists, remove it to recreate it from scratch if(networkID != -1) { wifiManager.removeNetwork(networkID); } // Create a new WiFi configuration wifiConfiguration.SSID = SSID; wifiConfiguration.preSharedKey = PSK; wifiConfiguration.hiddenSSID = false; wifiConfiguration.status = WifiConfiguration.Status.ENABLED; wifiConfiguration.allowedAuthAlgorithms.set(WifiConfiguration.AuthAlgorithm.OPEN); wifiConfiguration.allowedKeyManagement.set(WifiConfiguration.KeyMgmt.WPA_PSK); wifiConfiguration.allowedGroupCiphers.set(WifiConfiguration.GroupCipher.CCMP); wifiConfiguration.allowedGroupCiphers.set(WifiConfiguration.GroupCipher.TKIP); wifiConfiguration.allowedPairwiseCiphers.set(WifiConfiguration.PairwiseCipher.CCMP); wifiConfiguration.allowedPairwiseCiphers.set(WifiConfiguration.PairwiseCipher.TKIP); wifiConfiguration.allowedProtocols.set(WifiConfiguration.Protocol.RSN); // Catch Enumeration IpAssignment and ProxySettings from WifiConfiguration Enum ipAssignment = catchEnumIpAssignmentFromWifiConfiguration(); Enum proxySettings = catchEnumProxySettingsFromWifiConfiguration(); // Set IP address, gateway, DNS, etc try { Log.d(TAG, "Try to set IP, gateway and DNS"); setIpAssignment(ipAssignment, wifiConfiguration); Log.d(TAG, "IpAssignment: Ok"); setProxySettings(proxySettings, wifiConfiguration); Log.d(TAG, "ProxySettings: Ok"); setIpAddress(InetAddress.getByName("192.168.2.100"), 24, wifiConfiguration); Log.d(TAG, "IpAddress: Ok"); setGateway(InetAddress.getByName("192.168.2.1"), wifiConfiguration); Log.d(TAG, "Gateway: Ok"); setDNS(InetAddress.getByName("192.168.2.1"), wifiConfiguration); Log.d(TAG, "DNS: Ok"); } catch(Exception e) { e.printStackTrace(); } // Add this new configuration to the wpa_supplicant file networkID = wifiManager.addNetwork(wifiConfiguration); if(networkID != -1) Log.d(TAG, "Succeed to update the WiFi configuration: " + networkID); else Log.d(TAG, "Failed to update the WiFi configuration"); // Save the new configuration on the wpa_supplicant if(wifiManager.saveConfiguration()) Log.d(TAG, "Succeed to save the wpa_supplicant"); else Log.d(TAG, "Failed to save the wpa_supplicant"); // Set the Wifi disable to be able to start the Access Point Log.d(TAG, "Set wifi disable"); wifiManager.setWifiEnabled(false); receiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { int wifiState = intent.getIntExtra(WifiManager.EXTRA_WIFI_STATE, WifiManager.WIFI_STATE_UNKNOWN); if ( wifiState == WifiManager.WIFI_STATE_DISABLED ) { Log.d(TAG, "Wifi disabled"); // When the Wifi is disable // Create the Access Point with the WiFi configuration try { Method m = wifiManager.getClass().getMethod("setWifiApEnabled", WifiConfiguration.class, boolean.class); boolean succeed = (Boolean) m.invoke(wifiManager, wifiConfiguration, true); if(succeed) Log.d(TAG, "Succeed to set wifi AP"); else Log.d(TAG, "A problem occured while setting the wifi AP"); } catch (Exception e) { Log.e(TAG, "Failed to set wifi AP", e); } } } }; registerReceiver(receiver, new IntentFilter(WifiManager.WIFI_STATE_CHANGED_ACTION)); } protected String getWifiApState() { try { Method m3 = wifiManager.getClass().getMethod("getWifiApState"); return "WiFi Ap State: " + String.valueOf(m3.invoke(wifiManager)); } catch (NoSuchMethodException e1) { e1.printStackTrace(); } catch (IllegalArgumentException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } return null; } protected WifiConfiguration getWifiApConfiguration() { WifiConfiguration wifiConfiguration = null; try { Method m4 = wifiManager.getClass().getMethod("getWifiApConfiguration"); wifiConfiguration = (WifiConfiguration) m4.invoke(wifiManager); } catch (Exception e) { e.printStackTrace(); } return wifiConfiguration; } protected String isWifiApEnabled() { try { Method m = wifiManager.getClass().getMethod("isWifiApEnabled"); if((Boolean) m.invoke(wifiManager)) return "WiFiAP enabled"; else return "WiFiAP not enabled"; } catch (Exception e) { e.printStackTrace(); } return null; } protected String numberOfClientsConnected() { int macCount = 0; BufferedReader br = null; try { br = new BufferedReader(new FileReader("/proc/net/arp")); String line; while ((line = br.readLine()) != null) { String[] splitted = line.split(" +"); if (splitted != null &amp;&amp; splitted.length &gt;= 4) { String mac = splitted[3]; if (mac.matches("..:..:..:..:..:..")) { macCount++; } } } } catch (Exception e) { e.printStackTrace(); } finally { try { br.close(); } catch (IOException e) { e.printStackTrace(); } } return String.valueOf(macCount); } @SuppressWarnings({ "unchecked", "rawtypes" }) protected Enum catchEnumIpAssignmentFromWifiConfiguration() { Enum DHCP = null; try { Class&lt;Enum&gt; enumIpAssignment = (Class&lt;Enum&gt;) Class.forName("android.net.wifi.WifiConfiguration$IpAssignment"); DHCP = Enum.valueOf(enumIpAssignment, "DHCP"); } catch (ClassNotFoundException e) { e.printStackTrace(); } return DHCP; } @SuppressWarnings({ "unchecked", "rawtypes" }) protected Enum catchEnumProxySettingsFromWifiConfiguration() { Enum ProxySet = null; try { Class&lt;Enum&gt; enumProxySettings = (Class&lt;Enum&gt;) Class.forName("android.net.wifi.WifiConfiguration$ProxySettings"); ProxySet = Enum.valueOf(enumProxySettings, "NONE"); } catch (ClassNotFoundException e) { e.printStackTrace(); } return ProxySet; } public static void setIpAssignment(Object assign , WifiConfiguration wifiConf) throws SecurityException, IllegalArgumentException, NoSuchFieldException, IllegalAccessException { setEnumField(wifiConf, assign, "ipAssignment"); } public static void setProxySettings(Object assign , WifiConfiguration wifiConf) throws SecurityException, IllegalArgumentException, NoSuchFieldException, IllegalAccessException { setEnumField(wifiConf, assign, "proxySettings"); } @SuppressWarnings({ "rawtypes", "unchecked" }) public static void setIpAddress(InetAddress addr, int prefixLength, WifiConfiguration wifiConf) throws SecurityException, IllegalArgumentException, NoSuchFieldException, IllegalAccessException, NoSuchMethodException, ClassNotFoundException, InstantiationException, InvocationTargetException { Object linkProperties = getField(wifiConf, "linkProperties"); if(linkProperties == null) return; Class laClass = Class.forName("android.net.LinkAddress"); Constructor laConstructor = laClass.getConstructor(new Class[]{InetAddress.class, int.class}); Object linkAddress = laConstructor.newInstance(addr, prefixLength); ArrayList mLinkAddresses = (ArrayList)getDeclaredField(linkProperties, "mLinkAddresses"); mLinkAddresses.clear(); mLinkAddresses.add(linkAddress); } @SuppressWarnings({ "rawtypes", "unchecked" }) public static void setGateway(InetAddress gateway, WifiConfiguration wifiConf) throws SecurityException, IllegalArgumentException, NoSuchFieldException, IllegalAccessException, ClassNotFoundException, NoSuchMethodException, InstantiationException, InvocationTargetException { Object linkProperties = getField(wifiConf, "linkProperties"); if(linkProperties == null)return; Class routeInfoClass = Class.forName("android.net.RouteInfo"); Constructor routeInfoConstructor = routeInfoClass.getConstructor(new Class[]{InetAddress.class}); Object routeInfo = routeInfoConstructor.newInstance(gateway); ArrayList mRoutes = (ArrayList)getDeclaredField(linkProperties, "mRoutes"); mRoutes.clear(); mRoutes.add(routeInfo); } @SuppressWarnings("unchecked") public static void setDNS(InetAddress dns, WifiConfiguration wifiConf) throws SecurityException, IllegalArgumentException, NoSuchFieldException, IllegalAccessException { Object linkProperties = getField(wifiConf, "linkProperties"); if(linkProperties == null)return; ArrayList&lt;InetAddress&gt; mDnses = (ArrayList&lt;InetAddress&gt;)getDeclaredField(linkProperties, "mDnses"); mDnses.clear(); mDnses.add(dns); } public static Object getField(Object obj, String name) throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException { Field f = obj.getClass().getField(name); Object out = f.get(obj); return out; } public static Object getDeclaredField(Object obj, String name) throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException { Field f = obj.getClass().getDeclaredField(name); f.setAccessible(true); Object out = f.get(obj); return out; } public static void setEnumField(Object obj, Object value, String name) throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException { Field f = obj.getClass().getField(name); f.set(obj, value); } } </code></pre> <p>This code works fine on my Nexus 7. It creates an Access Point. My laptop see the network link this: <img src="https://i.stack.imgur.com/QcC4c.png" alt="enter image description here"></p> <p>It asks me to enter the WPA key. I need to write it wrapped with quotes whether it does not work (<code>"helloworld"</code>).</p> <p>After that, my laptop is connected to the network but with the software <a href="http://www.xirrus.com/Products/Wi-Fi-Inspector.aspx" rel="nofollow noreferrer">Xirrus</a> I realized that the DHCP module doesn't give any IP address. </p> <h2>Logs:</h2> <p>I get two interesting logs. This one is when I start the application: </p> <pre><code>E/hostapd(): Configuration file: /data/misc/wifi/hostapd.conf E/hostapd(): HT (IEEE 802.11n) in 11b mode is not allowed, disabling HT capabilites I/hostapd(): rfkill: Cannot open RFKILL control device W/hostapd(): wlan0: Could not connect to kernel driver E/hostapd(): Using interface wlan0 with hwaddr 02:1a:11:fd:32:58 and ssid "\"Awesome Access Point\"" E/hostapd(): random: Cannot read from /dev/random: Try again I/hostapd(): random: Only 0/20 bytes of strong random data available from /dev/random I/hostapd(): random: Allow operation to proceed based on internal entropy </code></pre> <p>And this one is when I connect and disconnect my laptop from/to the Access Point: </p> <pre><code>I/hostapd(): wlan0: AP-STA-DISCONNECTED 00:27:10:ca:f0:80 I/hostapd(): wlan0: AP-STA-CONNECTED 00:27:10:ca:f0:80 </code></pre> <h2>Questions:</h2> <ul> <li>If you think that I'm doing the wrong way, could you tell me a better way? </li> <li>Do you know why I didn't get IP address from the DHCP module? </li> <li>Do you know I could get more information/logs from the DHCP module?</li> </ul> <p>Thank you for your support.</p>
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    1. COHave you had any success with this project?
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    2. COUnfortunately not really. I decided to change the project structure to make it easier to develop. Now I generate the Wifi from my WiFly card and my Nexus 7 connects to this network thanks to an Android Scala application which I wrote.
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      1. USDavid Guyon
    3. COSome notes for others pursuing this: My research so far has led me to that there is no IPV4LL link local address being generated. The android dhcpcd client daemon *should* generate an IPV4LL by default, but doesn't. I tried installing BusyBox and using the zcip (zero configuration ip) utility to generate a link local IPV4LL but get an error regarding wlan0 permission access denied even though it is run as root.
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