Android :: Way To Write Async Socket With Phone?
Jul 14, 2009
I am developing a program that needs async socket. I am new to Android and Java. As I can see in the document, to write network program, I got Socket and SocketChannel, but it seems they are all sync socket, it means, I need an extra thread to call blocking read, write... and etc. Here comes the problem, my program is a chat room, the communicate is not linear, I have no idea when the server will send a message to me, if I read in that thread to wait message from server, but the user want to send message to server, the reading function blocked forever, if there is no incoming data, then the pending outgoing message will not be sent. That's why I need async socket. So my question is: How to write async socket under Android environment?
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Jun 29, 2010
We have a simple client server architecture between our mobile device and our server both written in Java. An extremely simple ServerSocket and Socket implementation. However one problem is that when the client terminates abruptly (without closing the socket properly) the server does not know that it is disconnected. Furthermore, the server can continue to write to this socket without getting any exceptions. Why? According to documentation Java sockets should throw exceptions if you try to write to a socket that is not reachable on the other end!
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Nov 12, 2009
Essentially Im trying to get many many java clients connect to a socket on my ColdFusion server (Using the Socket Gateway). However before i even start to code this, Im a little confused about sockets and their performance. First of all, are sockets meant for many(1000+) clients connecting to one socket (say port 2202) on one server? How is the performance if all there waiting for is basically a ping, or something such that when these clients receive this "ping" they can go get some new data.
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Jul 15, 2010
I am writing an Android app that should exchange data to a server over Bluetooth, with the server side on a PC running Ubuntu, using the bluez library, in C (or C++).
My Android app fails (IOException) when I try to connect to my server socket on the PC.
Here is essentially what I in the java code (in Android, full eclipse project here: http://dl.dropbox.com/u/2968234/ThinBTClient.zip)
CODE:...........
This throws IOException after a timeout of 10seconds or so.
On the server side (in Ubuntu 8.10), I basically set up a Bluetooth server socket, along the lines described in the example bluez/sdp-register.c
Down below is my C++ program. To compile it do
g++ -I/usr/include/glib-2.0/ -I/usr/lib/glib-2.0/include -o bt_server bt_server.cpp -lbluetooth
I can do the reverse succesfully, i.e. create a server socket in Android and connect from Linux, however this is not what I want to do!
I think either the problem has to do with my config of Ubuntu.
CODE:................
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Mar 17, 2010
I noticed that if the Android phone is listening on a ServerSocket on the 3G network, and is then put to sleep with the power button, it no longer listens for incoming connections. The incoming TCP connection does not wake up the phone. Is this there a way to enable waking up a sleeping phone on incoming Server Socket connections, the way that incoming data on a regular Socket does?
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Oct 27, 2010
In my android application i am trying to run a application using GPRS connection and not WIFI.When tried to run in wifi the app runs fine.The browser works fine with the APN settings set but when trying to connect to server using my application it gives me socket exception.I am using the below permissions in manifest file.
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses- permission>
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"></uses-permission>
<uses-permission android:name= "android.permission.CHANGE_NETWORK_STATE"></uses-permission>
<uses-permission android:name= "android.permission.WRITE_APN_SETTINGS" ></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" ></uses-permission>
I am receiving Socket not connected exception.Is there any other permission which i need to add for using GPRS connection other than WIFI.
10-27 18:26:19.689: WARN/CalSyncSvc(166): com.motorola.blur.service.email.protocol.activesync.ASException: Problem executing HTTP POST
10-27 18:26:19.689: WARN/CalSyncSvc(166): at com.motorola.blur.service.email.protocol.activesync.ActiveSyncMgr.sendRequest(Unknown Source)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at com.motorola.blur.service.email.protocol.activesync.ActiveSyncMgr.sendXMLCommandNoProvisoning(Unknown Source)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at com.motorola.blur.service.email.protocol.activesync.ActiveSyncMgr.sendXMLCommand0(Unknown Source)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at com.motorola.blur.service.email.protocol.activesync.ActiveSyncMgr.sendXMLCommand(Unknown Source)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at com.motorola.blur.service.email.protocol.activesync.ActiveSyncMgr.sendFolderSyncCommand(Unknown Source)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at com.motorola.blur.service.email.protocol.activesync.ProviderAPI.sendFolderSync(Unknown Source)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at com.motorola.blur.service.email.protocol.activesync.ProviderAPI.updateMapFromFolderSync(Unknown Source)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at com.motorola.blur.service.email.protocol.activesync.ProviderAPI.updateFromFolderSync(Unknown Source)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at com.motorola.blur.calendar.sync.activesync.SyncService.syncAccount(Unknown Source)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at com.motorola.blur.calendar.sync.activesync.SyncService$QueueEntry.run(Unknown Source)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:416)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:256)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at java.util.concurrent.FutureTask.run(FutureTask.java:122)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:648)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:673)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at java.lang.Thread.run(Thread.java:1058)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at com.motorola.blur.util.concurrent.BlurThreadFactory$BlurPooledThread.run(Unknown Source)
10-27 18:26:19.689: WARN/CalSyncSvc(166): Caused by: java.net.SocketTimeoutException: Socket is not connected
10-27 18:26:19.689: WARN/CalSyncSvc(166): at org.apache.harmony.luni.platform.OSNetworkSystem.connectStreamWithTimeoutSocketImpl(Native Method)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at org.apache.harmony.luni.platform.OSNetworkSystem.connectStreamWithTimeoutSocket(OSNetworkSystem.java:140)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at org.apache.harmony.luni.net.PlainSocketImpl.connect(PlainSocketImpl.java:229)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at org.apache.harmony.luni.net.PlainSocketImpl.connect(PlainSocketImpl.java:521)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at java.net.Socket.connect(Socket.java:1019)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at org.apache.http.conn.ssl.SSLSocketFactory.connectSocket(SSLSocketFactory.java:317)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:129)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:348)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
10-27 18:26:19.689: WARN/CalSyncSvc(166): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
10-27 18:26:19.689: WARN/CalSyncSvc(166): ... 17 more
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Feb 23, 2010
Im using a web service, so I want to use an async thread for the HTTP authentication request and another thread later to make additional service requests while my main thread runs.Would like to see a good example of how to do this and how to show busy messages somehow in main app. How does the main app know when the thread finished? And what if my thread encounters exceptions, how do I deal with that?HTTP requests are sent later, use the same cookies setup up by the first auth request, so will the later requests pick up the same cookies and just work?
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Nov 22, 2010
I just have a concern about AsycnTask. If i have one activity which starts a async task. Now that activity goes in background and new activity gets opened & visible to us.
So the async task opened by previous activity stops or it still keeps going in background or it pauses or stops ?
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Dec 21, 2009
In the documentation, I read that it is not possible for executing 2 Async Tasks. If execute is called again, it should throw an exception.
The following is given under the heading of "Threading Rules", and i quote:
"The task can be executed only once (an exception will be thrown if a second execution is attempted.)"
I wish to understand the meaning of this statement.
Does this mean, that if i try and execute the same task twice (concurrently) when the first execution of the task was still going on...an exception will be thrown ? Will i need to wait for the completion of the first task, before i spawn a second task ?
A possible use case:
The user wishes to download a set of files. He clicks on the download button by providing the URL. When the first download is still going on, he wishes to download another file and provides another URL. Both these user actions are serviced by a DownloadTask, that extends the AysncTask.
If i wish to change this default behavior, is there a configuration option?
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Jun 4, 2010
How do you create unit tests for an Android activity that starts async tasks in onCreate? I would like to test the result of these tasks.
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Jul 28, 2010
I've got the URL of a .png image, that needs to be downloaded and set as a source of an ImageView. I'm a beginner so far, so there are a few things I don't understand:
1) Where do I store the file?
2) How do I set it to the ImageView in java code?
3) How to correctly override the AsyncTask methods?
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Jul 16, 2010
What is the difference between Service, Async Task & Thread. If i am not wrong all of them are used to do some stuff in background. So, how to decide which to use and when?
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Jun 12, 2010
I read somewhere (and have observed) that starting threads is slow. I always assumed that AsyncTask created and reused a single thread because it required being started inside the UI thread.The following (anonymized) code is called from a ListAdapter's getView method to load images asynchronously. It works well until the user moves the list quickly, and then it becomes "janky".final File imageFile = new File(getCacheDir().getPath() + "/img/" + p.image);image.setVisibility(View.GONE);view.findViewById(R.id.imageLoading).setVisibility(View.VISIBLE);
(new AsyncTask<Void, Void, Bitmap>() {
@Override
protected Bitmap doInBackground(Void... params) {
try {Bitmap image;
if (!imageFile.exists() || imageFile.length() == 0) {
image = BitmapFactory.decodeStream(new URL(
"http://example.com/images/"
+ p.image).openStream());
image.compress(Bitmap.CompressFormat.JPEG, 85,
new FileOutputStream(imageFile));
image.recycle();
}image = BitmapFactory.decodeFile(imageFile.getPath(),
bitmapOptions);
return image;
} catch (MalformedURLException ex) {
// TODO Auto-generated catch block
ex.printStackTrace();
return null;
} catch (IOException ex) {
// TODO Auto-generated catch block
ex.printStackTrace();
return null;
@Override
protected void onPostExecute(Bitmap image) {
if (view.getTag() != p) // The view was recycled.
return;
view.findViewById(R.id.imageLoading).setVisibility(
View.GONE);
view.findViewById(R.id.image)
.setVisibility(View.VISIBLE);
((ImageView) view.findViewById(R.id.image))
.setImageBitmap(image);
}}).execute();I'm thinking that a queue-based method would work better, but I'm wondering if there is one or if I should attempt to create my own implementation.
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Nov 11, 2009
I have the following code...
CODE:.................
My mClient get method is a simple HttpClient execute with an output buffer to read the input stream, so it's very trivial. Everytime I execute this task UnknownHostException will be triggered which will in turn call onTaskError on my currect Activity, but I still get a RuntimeException, but I don't see why. Maybe it's because it's late and i've done about 12 hours of writing code so it's something simple I just can't see?
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Nov 2, 2010
In my android application i am using a loading screen,processed by Async task.In do in background of this task i would like to display a alert whenever an upgraded version exist in the server.
Could you please let me know if there is any way that i can do it in android.
The code is.
CODE:.................
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Sep 30, 2010
I want to write game for Android and I need to use inside AI phone slope in some way ( in degree or any other measure). Can anybody tell me how to do that(link or code sample) ?
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Oct 10, 2010
I have been searching for an answer for this for some time now. I have an async task that downloads the database needed for my app, while this is downloading my app cant do anything as all the data it references is in this file, i have the app waiting for the file to be downloaded but i am attempting to show a progress dialog so the user knows something is happening while they wait for this to happen.however nothing shows up i have also tried directly calling ProgressDialog.show in the pre execute and moving this to the calling activity with no luck.
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Mar 5, 2010
I have a simple app and I'm using the AsyncTask to test out a background process, for clearness purposes I've opted to put my AsyncTask in a separate class rather than in an inner class, which where my problems begin, this is my AsyncTask. Code...
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Apr 24, 2010
I've got an Android activity which grabs an RSS feed from a URL, and uses the SAX parser to stick each item from the XML into an array. This all works fine but, as expected, takes a bit of time, so I want to use AsyncActivity to do it in the background. The line items = parser.getItems() works fine - items being the arraylist containing each item from the XML. The problem I'm facing is that on starting the activity, the ProgressDialog which i create in onPreExecute() isn't displayed until after the doInBackground() method has finished. i.e. I get a black screen, a long pause, then a completely populated list with the items in. Why is this happening? Why isn't the UI drawing, the ProgressDialog showing, the parser getting the items and incrementally adding them to the list, then the ProgressDialog dismissing?
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Jul 30, 2013
I have read quite a good books & blogs about the Background work process in Android and updating the UI.
I have learned few way like using a Service with Intent, Using AsynTask, Using a Bind Service with a Intent and so..
What is the rule of thumb using this, i mean when to use what?
I am just learning to code in JAVA & Android.
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Nov 20, 2010
Please tell that In which topics of Java, One should already be an expert, in order to write Android Applications?
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Oct 20, 2010
I am just getting into android development, can anyone guide me how I can write an mp3 player?
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Nov 9, 2010
I am writing an application which requires screen saver. when the application runs in foreground and no body touch it for a while, it will automatically launch screen saver.
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Aug 26, 2009
I have written an android app that needs the GPS capabilities of the phone. If GPS is activated everything works fine, but if it is not i get an error. So my question: Is it possible to write code that is activating GPS on the phone? I found a forum post that it is not possible because of security reasons. Is this true?
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May 15, 2009
In logger_event structure, it exists msg[] as payload's message. Just I'm curious that how to write the payload's message in Android.
The reason is that I want to change the specific part of the msg array, for example msg[0] do always 05 when the msg exists.
If you know anythig about this question, plz help me.
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Nov 18, 2009
Is it possible to write the code/compile Android application on one machine and debug it remotely on the emulator launched on another? I'm sick and tired of the emulator constantly eating half of my laptop's processor.
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Feb 7, 2010
I am very new to android. The Eclipse and the Emulator is running and I have bought an device already. I want to write a little UPnP- Discover-Application first. I used CyberLinkForJava under Java some years ago. I read on this list (2010/1/29) that this framework can be used under android too. Like mentioned in the post from skonno I downloaded the code via svn from sourceforge and copied the trunk/cyberlink/upnp-stack/src/main/ java section into the source folder of my android project. Then I`d got errors in XercesParse.java and kXML2Parser.java. If I delete this classes it runs without errors. But the code from the cyberlink documentation. Code...
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Aug 23, 2010
I am downloading some images from website using xmlrpc now i want write the url of those images into xml files how to add data to exiting xml file in android
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Apr 5, 2010
I want to figure out how to detect when the phone wakes up from being in the black screen mode and write a handler for that event. Is that possible? It seems like this would be something a Broadcast Receiver should handle? Or is there a better or more proper way?
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Jan 7, 2010
I am a Java professional. Now I'd like to write an application for the Android platform.
What is the initial step I need to take?
How does my Java programming experience help in this case?
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