Develop Reference

Android call method but don't work on wifi but work on gprs

we work with xamarin android and visual studio 2015.
we have an app who works since several months fine :)
This app when it starts call a webservice for to retrieve some data in json format.
All work fine, but last week we have a problem and we are COMPLETY lost about it !
Since last week, for one device when it call the web service we receive this error in the catch exception :
unable to read data from the transport connection Connection reset by peer ...
Here is it the method on the device who call the WS:
public override HttpResult ExecuteGet(Uri target)
{
var client = new HttpClient();
client.MaxResponseContentBufferSize = 25600000;
try
{
var response = client.GetAsync(target).Result;
if (response.IsSuccessStatusCode)
{
var content = response.Content.ReadAsStringAsync().Result;
return new HttpResult(content, null, null);
}
return new HttpResult(null, " ERROR MESSAGE ", response.StatusCode.ToString());
}
catch (Exception e)
{
return new HttpResult(null, " ERROR MESSAGE", e.Message);
}
}
well, now with the same device if we stop the wifi and call the webservice in GPRS that work.
Also we have two wifi, we also have noticed if the device connect on the second wifi and try to call the web service => that's work !
After talk with some colleague, they tell me to look to update my android version of the device , or wifi app on the device but for me the first thing we need to do will be to compare wifi 1 and wifi 2.
My question is, how i can compare two wifi ?
All suggestion are welcome because we search and we find nothing ...
Thanks for all guys that's really great to share your knowledge ...

How to get my own endpointId with Nearby Connections?

With Nearby Connections, each device has an endpointId, something similar to zkHk.
Getting the endpointId of others is trivial since it is returned by the API when scanning or connecting to other devices.
I must miss something, but I cannot find a way to get my own endpointId (apart implementing a mechanism where a connected peer echoes my id). It can be useful for some protocols where I want to follow what is sent to who.
The only thing I found is getLocalEndpointName but it returns my name, not my id. Even though it seems the C++ version of Nearby have it!
Do you have some ideas for Java/Kotlin? I specifically seek to get the endpointId, and not use alternatives like using a kind of GUID in the localendpoint name as a replacement.
Edit: Some example of usage
1) For instance, it can be interesting to implement some network mesh protocols. Several devices are interconnected making a global network, and each device add its endpointId in the incoming payload before sending it again, so others can check if they should send the payload to a device that already has it.
2) I may also want to specifically send a packet from device A to C through B acting as a relay, and add some "from: A" and "to: C" field in the payload so the network would know how to route the data and avoid some retransmission cycles. It is simpler to do that with endpointId since each device has a list of endpointId to which it is connected.
3) It can also be interesting for debug purpose. If I do some tests with a phone connected to several others (e.g. star network), it is easier to know from which phone a new piece of data is coming, all the more if I want to use name for another purpose.
Note: all of that could be done differently (e.g. use some unique identifier for the "name" of the devices and check that instead of the endpointId) but it seems a little cumbersome. All the more since endpointId guarantee a kind of unicity, whereas I must enforce it for the name. Moreover there isn't lots of information I can have on another device before exchanging data (only endpointId and name), so I feel I remove my last metadata slot if I use name as a substitute for endpointId.

As of today, you can't get your own endpoint id. We didn't see a reason you'd need it. Can you give a more detailed example of an algorithm where you need to know your own id?

i think you want to get your endpointId and sent its to other devices to know you again ?
if yes
let's think like that :
other devices will get your EndpointID and save it every time you connect to them
1)you have an Arrylist<EndPointObject> listOfUsers where EndPointObject it's an Object contain informations about Connected Endpoint Device (you create this class).
we w'ill use this Arry list to save recieved Endpoint informations
2)you need to make EndPointObject class Serializable by implements Serializable,you are doing that to make it able to be converted to Byte[] and send it in payload
public class EndPointObject implements Serializable
{
String endpointId ;
.
.
.
}
3)this is the Converting class add it to your project
public class SerializeHelperForPayLoad {
public static byte[] serialize(Object object) throws IOException {
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);
// transform object to stream and then to a byte array
objectOutputStream.writeObject(object);
objectOutputStream.flush();
objectOutputStream.close();
return byteArrayOutputStream.toByteArray();
}
public static Object deserialize(byte[] bytes) throws IOException, ClassNotFoundException{
ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes);
ObjectInputStream objectInputStream = new ObjectInputStream(byteArrayInputStream);
return objectInputStream.readObject();
}
}
4) now the strategy is every time you connect to an endpoint Device you will exchange yours EndpointObject informations,so in payloadcallback
PayloadCallback mPayloadCallback =
new PayloadCallback() {
#Override
public void onPayloadReceived(String endpointId, Payload payload) {
if (payload.getType() == Payload.Type.BYTES) {
try{
onDataReceived(endpointId, SerializeHelperForPayLoad.deserialize(payload.asBytes()));
} catch (IOException | ClassNotFoundException e) { e.getMessage(); }
}
}
// onData recieved void
void onDataReceived(String endpointId, Object object) {
// do something with your Object
EndPointObject recieved_user_info = new EndPointObject();
if (object.getClass() == EndPointObject.class){
//casting
recieved_user_info = (EndPointObject) object;
//now add his end pointid to his information
recieved_user_info.setEndpointId(endpointId);
listOfUsers.add(recieved_user_info);
}
}
i'm very new in nearby technology ,but i hope that's helpful ,
by this way you can ask other end endpoint to send you your own endpointid every time

dronekit-android API addMavlinkObserver causes system crash

I am using dronekit-android packages that can successfully connect to PX4 board. However, I try to receive the mavlink message in a while 1 thread, the receive API addMavlinkObserver causes the system crash.
After the drone is connected, I simply call this function upon pressing a button and it crashes.
this.drone.addMavlinkObserver(new MavlinkObserver() {
#Override
public void onMavlinkMessageReceived(MavlinkMessageWrapper mavlinkMessageWrapper) {
//Log.d("Received Mavlinks:", mavlinkMessageWrapper.getMavLinkMessage().toString());
Toast.makeText(getApplicationContext(), "MAV receive " + mavlinkMessageWrapper.getMavLinkMessage().toString(),Toast.L‌​ENGTH_LONG).show();
}
})
Does anyone have any idea?

Detecting toast messages

I don't think this is possible, as I haven't found anything in the SDK documentation (yet).
But I could do with knowing if its possible to write an application which logs Toast messages. Logging which application showed it and what the message displayed contained.
This is an entirely personal endeavour to create an app which can detect the toast messages. Because something on my phone is creating a toast saying "Sending..." about once per day, and for the life of me I can't track down the offending application (Service class). I thought it might be GMail or Evernote, but there toast messages for sending are slightly different. I'm going for building an app because 1) I don't know if LogCat would show anything, and 2) I don't want to keep my personal/dev phone plugged in to a PC all the time (as the "Sending..." message occurs so infrequently).

It's possible to catch Messages/Notifications with an Accessibility Service, have a look at that.
You can extend the class AccessibilityService and override the method onAccessibilityEvent() to implement something like this:
public void onAccessibilityEvent(AccessibilityEvent event) {
if (event.getEventType() != AccessibilityEvent.TYPE_NOTIFICATION_STATE_CHANGED)
return; // event is not a notification
String sourcePackageName = (String) event.getPackageName();
Parcelable parcelable = event.getParcelableData();
if (parcelable instanceof Notification) {
// Statusbar Notification
}
else {
// something else, e.g. a Toast message
String log = "Message: " + event.getText().get(0)
+ " [Source: " + sourcePackageName + "]";
// write `log` to file...
}
}
Note: This didn't work for me on Android 2.2 as it doesn't seem to catch Toasts, but it worked on Android 4.0+.

How to auto-accept Wi-Fi Direct connection requests in Android

I have 2 Android devices using WiFi Direct. On one device I can get information about the other device using the WifiP2pManager class, and request a connection to the other device. However when I request a connection, the other device pops up a little window and asks the user if they want to accept the connection request.
Is it possible to auto-accept these connection requests? I.E to be able to connect to the other device without user confirmation?

It can be easily done with the help of Xposed framework. You just need to replace the single method inside one of android java classes (see the link from snihalani's answer). But of course to use Xposed your device must be rooted. The main idea can be expressed in the following code (using Xposed)
#Override
public void handleLoadPackage(LoadPackageParam lpparam) {
try {
Class<?> wifiP2pService = Class.forName("android.net.wifi.p2p.WifiP2pService", false, lpparam.classLoader);
for (Class<?> c : wifiP2pService.getDeclaredClasses()) {
//XposedBridge.log("inner class " + c.getSimpleName());
if ("P2pStateMachine".equals(c.getSimpleName())) {
XposedBridge.log("Class " + c.getName() + " found");
Method notifyInvitationReceived = c.getDeclaredMethod("notifyInvitationReceived");
final Method sendMessage = c.getMethod("sendMessage", int.class);
XposedBridge.hookMethod(notifyInvitationReceived, new XC_MethodReplacement() {
#Override
protected Object replaceHookedMethod(MethodHookParam param) throws Throwable {
final int PEER_CONNECTION_USER_ACCEPT = 0x00023000 + 2;
sendMessage.invoke(param.thisObject, PEER_CONNECTION_USER_ACCEPT);
return null;
}
});
break;
}
}
} catch (Throwable t) {
XposedBridge.log(t);
}
}
I tested it on SGS4 stock 4.2.2 ROM and it worked.
I guess the same could be done with the help of Substrate for android.

From my current understanding of the API, You cannot really accept connections automatically without user's intervention. You can initiate a connection, that doesn't require user intervention. If both of your devices are mobile devices, you will have to accept connection request on one end.
I have put this as a feature request in android project hosting.
You can monitor their response here: https://code.google.com/p/android/issues/detail?id=30880

Based on the comments, do you really need to connect to the devices if you just want to track and log the vehicles around you ?
I don't know the scope of the project, but you could simply use the WifiP2pDeviceList that you get when you request the peers in the WifiP2pManager. You could get the list of the devices (~= vehicles) around you and could log this.
Connection is useful if you want to send more detailed information I guess.

If you can modify the framework, you can ignore the accept window and direct send the "PEER_CONNECTION_USER_ACCEPT".
Base on Android 5.0, "frameworks/opt/net/wifi/service/java/com/android/server/wifi/p2p/WifiP2pServiceImpl.java".
You must find the "notifyInvitationReceived", and modify to ...
private void notifyInvitationReceived() {
/*Direct sends the accept message.*/
sendMessage(PEER_CONNECTION_USER_ACCEPT);
/*
... old code
*/
}