I'm looking at trying to implement a VPNService on Android for packet filtering and reporting and I have initially been looking at this project:
https://github.com/hexene/LocalVPN
As well as this I have been looking at Google's ToyVpn as a basis to understand what I can and can't do with a VPNService. The only issue with both is that start a non-blocking VPN when building the VPNService and then poll the file descrptor and then wait something like 100ms. Both have comments suggesting that this is not the way to do it. I'm assuming they run a non-blocking VPN because a blocking VPN is much more complicated?
I also assumed (wrongly) that adding the line
builder.setBlocking(true);
would fix things, but instead whilst the VPN service seems to do something, it doesn't seem to do anything useful because if you connect to it and open a browser session everything times out. It's almost as if adding this line causes packets to be dropped.
The aim is to get this as a blocking VPN so that I can eliminate the need for polling the file descriptor which I am sure is bad for battery life.
Just for anyone seeing this and having the same issue, this is a question that misses the mark. Turns out turning blocking on was OK, it's just that the polling loop was not setup to be blocking which causes deadlock.
Related
I am trying to build an NFC enabled application that transmits data to another device via Android Beam (pushing a NDEFMessage).
While I know there is a success callback void onNdefPushComplete(NfcEvent event), I can't find a failure callback, which would be really useful.
I tried to think of other way to sort of guess whether the transfer happened, if it succeeded or failed but cannot really find anything satisfying. Even a dirty timer would not work since I cannot know for sure when and even if the user actually starts the beam.
I feel pretty much bound by the API since the OS is handling most of the functionality and the application is only providing the message to send.
Any suggestions, something I might have missed? I'd rather avoid rooting the device if possible, but if it cannot be accomplished without tinkering with the core NFC code, then so be it.
Cheers
No, there is no such callback. Or a notification or anything that would give you a clue that things didn't worked.
Unfortunately.
In general the Android Beam API has not been designed with error handling in mind.
I have created a webserivce using C# on .NET and I'm consuming the same in an android application. At times while testing I notice that the web service is annoyingly slow and does not show results for minutes altogether. I don't want to put my user through this behavior of the application.
I am basically looking for a way such that the communication between the application and the web service can become faster.
PS: I am using asynctask function already to provide a separate thread while calling the web service. STILL it takes minutes at times to extract results from it.
Any help is appreciated!:]
I can't tell if you're saying the web service is slow or if it's just slow to be consumed on an Android device.
If the web service is slow on all devices I'd suggest first eliminating the possibility that it's just the speed of the web connection you're testing on. Obviously there isn't much that can be done about that. If the service is simply slow to respond I'd recommend running some profilers to determine where the slowdown is. If it can't be made more efficient perhaps this is a task better suited to be first requested and placed in a queue. When the task is complete alert the device that the data is ready.
If the Android device is slow I'd also recommend some profiling to determine what's eating up the processor.
Sorry if I'm stating the obvious here but these are the only options I can think of.
I have having problems with a WSDL/SOAP service call in an app I have built in flash builder for mobile. I have connected to the service using flash builders built in data/services functionality.
For the most part, the service call works perfectly but once in a while it will cause the app to crash - on my android device it completely locks up (spinning animation stops) and then Android informs me that the app is not responding and asks if I want to close it.
The crash appears to occur quite frequently but not with any pattern. One time it happened on my third attempt, another time it took approximately 30, a couple of times I could not get it to happen and most times it occurs somewhere in between.
It appears that the crash happens after a service call is made but before any response is received. Neither the success or the fault listeners are ever fired. I am very confident that I am sending exactly the same variables to the service every time.
I have used web service calls in other apps without trouble so I have to assume there is something in this particular build that is causing problems but I can't seem to find anything.
Any thoughts on possible causes, things to test or even a solution would be hugely appreciated.
Thank you,
Jamie
Your question lacks essential details, so now I can suggest you to setup Charles proxy and monitor you requests trough it.
If you send too many requests simultaneously, you shall not be confident in fault/result events as air runtime has limitations (in any case, it is a good practice to handle request timeout).
I'm currently trying to assess whether a project can be realised for Android. One major problem I see it that, since it's a P2P client, we'd have to keep a considerable amount of connections open when running. Now the connections do not transfer large amounts of data, it's more of a messaging system, so having a thread for each connection creates a useless overhead if we're reading a single message of 64 bytes every now and then.
So I was wondering whether there is support for non blocking IO such as select() or poll() on Linux.
Any suggestion?
Check out java.nio Sockets, Selectors, and Channels. Some links:
Android: Unbuffered IO
http://developer.android.com/reference/java/nio/channels/ServerSocketChannel.html
http://developer.android.com/reference/java/nio/channels/SocketChannel.html
http://www.developer.com/java/article.php/3837316/Non-Blocking-IO-Made-Possible-in-Java.htm
Or, maybe I didn't read your question right.
Of course. Once your application declares uses internet permission, you can do all normal linux networking things normally available to a non-root user in C using the NDK, and any of them from java that someone (possibly you if no one beat you too it) has bothered to write support for.
Well, one exception: your mobile provider probably won't permit incoming connections, and neither will most wifi routers unless you specially set them up to. But those are infrastructure issues rather than issues with android itself.
You will probably also need to come up with some combination of an Activity to provide the foreground UI and a Service to continue the actual transfers in the background with just a status bar icon showing.
All,
I'm developing an Android application that connects to other hardware on start up via TCP (over WiFi) . I'm pretty happy with the software that handles the connection -- it does a good job of establishing the socket connection as well as handling things when the connection is unexpectedly lost.
Unfortunately, my application currently just displays a blank, empty screen until the connection is established, and I expect that this sort of thing may produce unwarranted worry on the part of my users.
I can't figure out how to put up a start-up message informing the user that I have a towel and that there's no need to panic. Can anybody point me to a method for accomplishing this? I'll be happy with just about anything that's legible, whether graphical or textual.
Thanks,
R.
Whatever you choose, you need to get the startup screen displayed and more importantly start responding to UI events before the TCP connection is made - ie, you shouldn't do the TCP connection attempt on the UI thread, as if it takes longer than expected you may get an application not responding error.
Do the networking in AsyncTask (another thread, so it won't block the UI). Then you can display all kinds of progress indicators in the UI.
You could use a ProgressDialog. http://developer.android.com/reference/android/app/ProgressDialog.html