Develop Reference

How to connect to Bluetooth SPP using dot42?

After reading the dot42 comments and trolling Java examples I managed to setup a Bluetooth connection but fail to open the connection. I cannot determine the problem. I followed the docs step by step.
My target device is a HTC Explorer running on 2.3 Gingerbread. Here is my code.
//Target 2.3 (Gingerbread)
[assembly: Application("dot42Application1")]
[assembly: UsesPermission(Android.Manifest.Permission.BLUETOOTH)]
[assembly: UsesPermission(Android.Manifest.Permission.BLUETOOTH_ADMIN)]
namespace dot42Application1
{
[Activity]
public class MainActivity : Activity
{
private TextView txStatus;
protected override void OnCreate(Bundle savedInstance)
{
base.OnCreate(savedInstance);
SetContentView(R.Layouts.MainLayout);
// Find UI controls
txStatus = FindViewById<TextView>(R.Ids.txStatus);
Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
var bt = BluetoothAdapter.GetDefaultAdapter();
if (bt != null) //If device has not Bluetooth this will be null
{
if (bt.IsEnabled()) //Is Bluetooth device enabled?
{
var BT_My_Addr = bt.Address; //Get the devices MAC
var BT_Bonded = bt.GetBondedDevices().ToList(); //Get a list of bonded devices- I bonded to a BT2TTL Board earlier.
txStatus.Text = BT_My_Addr + System.Environment.NewLine; //Shows my MAC on screen.
string BT_Remote_Address = string.Empty;
foreach (var BTDevice in BT_Bonded) //Just searchging for string in bonded list
{
if (BTDevice.Name.Contains("linvor"))
{
BT_Remote_Address = BTDevice.Address;
}
}
//Gets remote device
var BT_Remote_Device = bt.GetRemoteDevice(BT_Remote_Address);
//Create a RFCOMM Socket to remote device using popular UUID ofr BT Serial boards
var BTsocket = BT_Remote_Device.CreateInsecureRfcommSocketToServiceRecord(Java.Util.UUID.FromString("00001101-0000-1000-8000-00805F9B34FB"));
//Call anyway to make sure there is no discvoerry in the backgorund. It slows stuff down.
bt.CancelDiscovery();
//Exception here? Dont know why :(
BTsocket.Connect();
//Suppsoed to dump 0 to 99999 to my listening serial device but I never get this far.
var BT_Out = BTsocket.GetOutputStream();
for (int i = 0; i < 99999; i++)
{
BT_Out.Write(Encoding.ASCII.GetBytes(i.ToString()));
}
}
else
{
txStatus.Text = "Bluetooth is disabled :(";
}
}
}
}
And this is what it shows after the socket creation
and the error...
What am I doing wrong? :(

I seem to have solved the problem by analysing various code snippets on the internet. I think the problem was trying to do everything in the OnCreate method. The steps I followed are the following:
Created a button on the main view (MainActivity.xml) and attached a onClick method.
Moved all the code OUT of the OnCreate method. (I think this allows the application to fully initialise.) Created an event handler for the button with two methods.
The two methods are the same as the code I posted in my original question. Just they are separated out and called when the user clicks the button.
findBT() Gets the default adapter. Checks if Bluetooth is enabled if not does the intent filter. Or if it is it will cycle through the bonded list and match a device name and store the BluetoohDevice in a variable. This is another thing that is different from my code. I do not use GetRemoteDevice I just assign the device from the BondedList to my global variable.
openBT() creates the RFCOMM socket (this did not work with unsecure - it threw an exception but using the secure method worked!)
You have to pair to the remote device using the Androids Bluetooth control panel. This code will not scan or connect to devices that are not paired. It will just throw null exceptions.
Also I left the target SDK 2.3.x but I am using the 4.x API.
-Disclosure. I am not a seasoned Android developer and just learning about the life cycle of Java applications in the Android context. I hope this can help other C# developers trying to do the same.

Can I turn on WiFi-Direct from code? on API-16 (Android 4.2.2)

I am developing an application with NFC and wifi direct. I get the MAC address using NFC and the Wifi Direct to transfer data. I call discoverpeers() and could get success. But there is no callback WIFI_P2P_PEERS_CHANGED_ACTION, the callback comes only when I go to settings and the select wifidirect.
This was discussed in the other question
Can I turn on WiFi-Direct from code? on Android API-14 (ICS)
"I'd like to add that WiFi direct on JB and above (at least on AOSP) is not active all the time - it only appears to be. If you look at listeners for WiFi direct, it turns itself off after some time. It turns itself back on if you open the wifi direct menu, however. You might have to have the host do a peer search or initialize itself in order to be able to be found. Likely a battery saving trick. I have also found that it's blocking, since as it accepts a connection, the entire system will lock up and fail to connect sometimes. (The system invitation) – Mgamerz "
Can anyone suggest the solution for the problem WIFI_P2P_PEERS_CHANGED_ACTION callback is not got and can get only when manually go to settings->wifi->tap on wifidirect
I used two devices Samsung galaxy nexus and nexus 7 both running on 4.2.2

There is no available API to enable wifiP2P but you can invoke method "enableP2p" from android settings 4.0.1
WifiP2pManager manager = (WifiP2pManager) getActivity().getSystemService(Context.WIFI_P2P_SERVICE);
Channel channel = manager.initialize(getActivity(), getActivity().getMainLooper(), null);
try {
Method method1 = manager.getClass().getMethod("enableP2p", Channel.class);
method1.invoke(manager, channel);
//Toast.makeText(getActivity(), "method found",
// Toast.LENGTH_SHORT).show();
} catch (Exception e) {
//Toast.makeText(getActivity(), "method did not found",
// Toast.LENGTH_SHORT).show();
}
To disable wifiP2P use this method
Method method1 = manager.getClass().getMethod("disableP2p", Channel.class);

Not from code. The user has to. That's why the demo has the link to wifi settings in the action bar.
When you call manager.discoverPeers(channel, new WifiP2pManager.ActionListener()
define onFailure and look at the reasonCode. If it's 0, then either the Wifi or WiFi direct is off.
If you look at the WiFi Direct demo app, the WifiDirectBroadcast Reciever, this piece of code looks at whether p2p is enabled specifically
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION.equals(action)) {
// UI update to indicate wifi p2p status.
int state = intent.getIntExtra(WifiP2pManager.EXTRA_WIFI_STATE, -1);
if (state == WifiP2pManager.WIFI_P2P_STATE_ENABLED) {
// Wifi Direct mode is enabled
activity.setIsWifiP2pEnabled(true);
} else {
activity.setIsWifiP2pEnabled(false);
activity.resetData();
}
Then when discover peers is called it looks at the variable set by setIsWifiP2pEnabled

thanks user3093354. to continue with your solution, in order to disable the p2p you have to invoke:
Method method1 = manager.getClass().getMethod("disableP2p", Channel.class);

//Try this it may be help you
WifiManager wifiManager = (WifiManager)this.getSystemService(this.WIFI_SERVICE);
wifiManager.setWifiEnabled(true); //True - to enable WIFI connectivity .
//False -disable WIFI connectivity.
//add this permissions in Manifest file :
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>

You can load the wifi driver from a command prompt with the desired concurrency level if you are rooted:
/system/bin/insmod /system/lib/modules/wlan.ko con_mode=3
These are the values:
typedef enum
{
VOS_STA_MODE=0,
VOS_STA_SAP_MODE=1,
VOS_P2P_CLIENT_MODE,
VOS_P2P_GO_MODE,
VOS_MONITOR_MODE,
VOS_FTM_MODE = 5,
VOS_IBSS_MODE,
VOS_P2P_DEVICE_MODE,
VOS_MAX_NO_OF_MODE
} tVOS_CON_MODE;
This is for an Atheros card.

Android DHCP enabled disabled check

I wanted to know if there is any way to check programmatically in android phone whether DHCP is enabled or disabled. (Assuming its possible to disable DHCP through some way or dhcpd is not running)

You can do the following to know if Android is currently using static IP adresses or DHCP attributed ones :
try {
if ( Settings.System.getInt(getContentResolver(),
Settings.System.WIFI_USE_STATIC_IP) == 0 )
/* Static ip addresses mode is not enabled */
;
} catch (SettingNotFoundException e) {
/* Do something smart here */
}
However, note that this method seems now deprecated and that it does not work across all devices (AVD for example).

Android - Detect if Wifi Requires Browser Login

My university has an open wifi access point, however it requires you to enter your e-mail before it allows you to use the web. My problem is that the Wifi is stupid in that it seems to drop my connection and force me to enter my e-mail again every 10 minutes.
I wanted to create my own app that I can use to automatically do this step for me, but I cannot seem to find any documentation for a nice and easy way to detect if a Wifi access point has a browser login page. Is there a way in Android to get this information, or is it just to see if my connection to something is always redirected to 1.1.1.1?

See the "Handling Network Sign-On" section of the HttpUrlConnection documentation:
Some Wi-Fi networks block Internet access until the user clicks through a sign-on page. Such sign-on pages are typically presented by using HTTP redirects. You can use getURL() to test if your connection has been unexpectedly redirected. This check is not valid until after the response headers have been received, which you can trigger by calling getHeaderFields() or getInputStream().
They have a snippet of sample code there. Whether this will cover your particular WiFi AP, I can't say, but it is worth a shot.

Ping an external IP address (like google.com) to see if it responds.
try {
Runtime runtime = Runtime.getRuntime();
Process proc = runtime.exec("ping -c 1 " + "google.com");
proc.waitFor();
int exitCode = proc.exitValue();
if(exitCode == 0) {
Log.d("Ping", "Ping successful!";
} else {
Log.d("Ping", "Ping unsuccessful.");
}
}
catch (IOException e) {}
catch (InterruptedException e) {}
The only downside is this would also indicate that a web login is required when there is simply no internet connectivity on the WiFi access point.
#CommonsWare I believe this is a better answer than opening a UrlConnection and checking the host, since the host doesn't always change even when displaying the redirect page. For example, I tested on a Belkin router and it leaves whatever you typed in the browser as is, but still displays its own page. urlConnection.getUrl().getHost() returns what it should because of this.

I think #FlyWheel is on the right path, but I would use http://clients1.google.com/generate_204 and if you don't get a 204, you know you are behind a captive portal. You can run this in a loop until you do get a 204 in which case you know you are not behind a captive portal anymore.
#FlyWheel wrote: The only downside is this would also indicate that a web login is required when there is simply no internet connectivity on the WiFi access point.
You can solve this by registering a receiver to android.net.conn.CONNECTIVITY_CHANGE. You can check if Wifi is ON and is connected by looking at the Supplicant State of the connection.
Here is a snippet, but I didn't run it:
WifiManager wm = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
WifiInfo wifiInfo = wm.getConnectionInfo();
SupplicantState suppState = wifiInfo.getSupplicantState();
if (wm.isWifiEnabled()) {
if (suppState == SupplicantState.COMPLETED){
// TODO - while loop checking generate_204 (FlyWheels code)Using intent service.
}
}
I can't remember if the SupplicantState is COMPLETED or ASSOCIATED, you will have to check that. You should use an IntentService for checking the generate_204 since broadcast receivers have a short lifetime.

I used the following code using google's 204 endpoint.
private boolean networkAvailable() {
ConnectivityManager mManager = (ConnectivityManager) getApplicationContext().getSystemService(Context.CONNECTIVITY_SERVICE);
if(mManager != null) {
NetworkInfo activeNetwork = mManager.getActiveNetworkInfo();
if(activeNetwork== null || !activeNetwork.isConnectedOrConnecting()){
return false;
}
}
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url("http://clients1.google.com/generate_204")
.build();
try {
Response response = client.newCall(request).execute();
if(response.code() != 204)
return false; // meaning it either responded with a captive html page or did a redirection to captive portal.
return true;
} catch (IOException e) {
return true;
}
}
Many applications including Google Chrome use http://clients1.google.com/generate_204 to verify that the the connection is not locked under captive portal.

The issue might rather be - today at least - that newer Android versions (5.1+?) keep the 3G/4G connection up and running until the wifi login actually leads to a fully functional wifi connection.
I haven't tried it, but maybe with the enum value CAPTIVE_PORTAL_CHECK of NetworkInfos DetailedState one can try to detect such a mode properly?

BUG or Normal Behavior on Android MAC-Address?

I am trying to get the MAC address, BSSID and LINK_speed of the Wifi. I notice that all three show up with values even when Wifi is turned off. I turn the phone off and then on again but do not turn wifi on. The app crashes on any interrogation of the three items and I cant try/catch the errors. If I turn wifi on then off I can interrogate the items and app runs fine. Its like BSSID and LINKSPEED are really 'LAST'BSSID and 'LAST'LINKSPEED. Is being blind to the MAC address after power on but not turning wifi on normal behavior? And is there a way to trap the error to keep from force close of the app?
WifiManager wifi;
wifi = (WifiManager) this.getSystemService(Context.WIFI_SERVICE);
WifiInfo wifiInfo = wifi.getConnectionInfo();
int ipAddress = wifiInfo.getIpAddress();
ipAddress = wifiInfo.getIpAddress();
//above work no matter whether wifi on or off before
String BSSID=wifiInfo.getBSSID(); //<<<<< ERRORS FORCE CLOSE IF NOT EVER CONNECTED
int WifiLinkSpeed=wifiInfo.getLinkSpeed(); printi("link speed",WifiLinkSpeed);
String MacAddress=wifiInfo.getMacAddress(); Log.e("MAC address",MacAddress);
//All three of these FORCE close if WIFI has never been turn on

Try this,
WifiManager wifiManager = (WifiManager) Settings.cntxt.getSystemService(Context.WIFI_SERVICE);
WifiInfo wifiInfo = wifiManager.getConnectionInfo();
strMacAddr = wifiInfo.getMacAddress();
if(strMacAddr==null) {
strMacAddr = "Unknown MAC";
}

Although you did say you tried try/catch... which errors/exceptions are you catching? Evidently not the right one(s).
It's been a while since I did any Android programming, but that's the crux of the matter... figuring out which exception is firing when you try those functions.
try {
// don't declare variables inside block, you'll limit scope
BSSID=wifiInfo.getBSSID(); //<<<<< ERRORS FORCE CLOSE IF NOT EVER CONNECTED
WifiLinkSpeed=wifiInfo.getLinkSpeed(); printi("link speed",WifiLinkSpeed);
MacAddress=wifiInfo.getMacAddress(); Log.e("MAC address",MacAddress);
//All three of these FORCE close if WIFI has never been turn on
}
catch { /* something bad happened, handle it */ }
// continue on since all is good in the world today...