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  • Reading data from a socket

    - by Bobby
    I am having issues reading data from a socket. Supposedly, there is a server socket that is waiting for clients to connect. When I write a client to connect() to the server socket/port, it appears that I am connected. But when I try to read() data that the server is supposedly writing on the socket, the read() function hangs until the server app is stopped. Why would a read() call ever hang if the socket is connected? I believe that I am not ever really connected to the socket/port but I can't prove it, b/c the connect() call did not return an error. The read() call is not returning an error either, it is just never returning at all.

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  • An existing connection was forcibly closed by the remote host

    - by peter
    I am working with a commercial application which is throwing a SocketException with the message, An existing connection was forcibly closed by the remote host This happens with a socket connection between client and server. The connection is alive and well, and heaps of data is being transferred, but it then becomes disconnected out of nowhere. Has anybody seen this before? What could the causes be? I can kind of guess a few causes, but also is there any way to add more into this code to work out what the cause could be? Any comments / ideas are welcome. Thanks.

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  • Syncronizing mobile phone contacts with contacts from social networks

    - by Pentium10
    I retrieve a JSON list of contacts from a social network site. It contains firstname, lastname, displayname, data1, data2, etc... What is the efficient way to quickly lookup my local phone contacts database and "match" them based on their name. Since there are firstname, lastname and displayname this can vary. What do you think, how can the best match be achieved? Also how do I make sure I don't parse for each JSON item the whole database I want to avoide having JSON_COUNT x MOBILE COUNT steps.

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  • How frequently IP packets are fragmented at the source host?

    - by Methos
    I know that if IP payload MTU then routers usually fragment the IP packet. Finally all the fragmented packets are assembled at the destination using the fields IP-ID, IP fragment offsets and fragmentation flags. Max length of IP payload is 64K. Thus its very plausible for L4 to hand over payload which is 64K. If the L2 protocol is Ethernet, which often is the case, then the MTU will be about 1600 bytes. Hence IP packet will be fragmented at the source host itself. However, a quick search about IP implementation in Linux tells me that in recent kernels, L4 protocols are fragment friendly i.e. they try to save the fragmentation work for IP by handing over buffers of size which is close to MTU. Considering these two facts, I am wondering about how frequently does the IP packet gets fragmented at the source host itself. Does it occur sometimes/rarely/never? Does anyone know if there are exceptions to the rule of fragmentation in linux kernel (i.e. are there situations where L4 protocols are not fragment friendly)? How is this handled in other common OSes like windows? In general how frequently IP packets are fragmented?

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  • How to do a true Java ping?

    - by stjowa
    I have a device on a network that I am attempting to ping through my Java program. Through my windows command prompt, I can ping the device address fine and do a tracert on the address fine. Online, I have seen that in order to do a ping through Java you have to do the following: InetAddress.getByName(address).isReachable(timeout); But, when I use this code on my device address, it always returns false in my program. I am using the correct IPv4 address with a good timeout value. Also, if I use a localhost address, it works fine. Why can I ping the device through cmd, but not through my program? I have heard in various places that this is not a true ping. Is there a better way to emulate a ping in Java? Thanks

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  • Android, NetworkInfo.getTypeName(), NullpointerException

    - by moppel
    I have an activity which shows some List entries. When I click on a list item my app checks which connection type is available ("WIF" or "MOBILE"), through NetworkInfo.getTypeName(). As soon as I call this method I get a NullpointerException. Why? I tested this on the emulator, cause my phone is currently not available (it's broken...). I assume this is the problem? This is the only explanation that I have, if that's not the case I have no idea why this would be null. Here's some code snippet: public class VideoList extends ListActivity{ ... public void onCreate(Bundle bundle){ final ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); ... listview.setOnItemClickListener(new OnItemClickListener(){ public void onItemClick(AdapterView<?> parent, View view, int position, long id) { ... NetworkInfo ni = cm.getActiveNetworkInfo(); String connex = ni.getTypeName(); //Nullpointer exception here if(connex.equals("WIFI")doSomething(); } }); } }

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  • android upload progressbarr not working

    - by pieter
    I'm a beginner in Android programming and I was tryinh to upload an image to a server. I found some code here on stackoverflow, I adjusted it and it still doesn't work. The problem is my image still won't upload. edit I solved the problem, I had no rights on the folder on the server. Now I have a new problem. the progresbarr doesn't work. it keeps saying 0 % transmitted does anyone sees an error in my code? import android.app.Activity; import android.app.AlertDialog; import android.app.Dialog; import android.app.ProgressDialog; import android.content.Context; import android.content.DialogInterface; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.location.Location; import android.location.LocationListener; import android.location.LocationManager; import android.os.AsyncTask; import android.os.Bundle; import android.util.Log; import android.view.View; import android.view.Window; import android.widget.Button; import android.widget.ImageView; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.net.HttpURLConnection; import java.net.URL; public class PreviewActivity extends Activity { /** The captured image file. Get it's path from the starting intent */ private File mImage; public static final String EXTRA_IMAGE_PATH = "extraImagePath" /** Log tag */ private static final String TAG = "DFH"; /** Progress dialog id */ private static final int UPLOAD_PROGRESS_DIALOG = 0; private static final int UPLOAD_ERROR_DIALOG = 1; private static final int UPLOAD_SUCCESS_DIALOG = 2; /** Handler to confirm button */ private Button mConfirm; /** Handler to cancel button */ private Button mCancel; /** Uploading progress dialog */ private ProgressDialog mDialog; /** * Called when the activity is created * * We load the captured image, and register button callbacks */ @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS); setContentView(R.layout.preview); setResult(RESULT_CANCELED); // Import image Bundle extras = getIntent().getExtras(); String imagePath = extras.getString(FotoActivity.EXTRA_IMAGE_PATH); Log.d("DFHprev", imagePath); mImage = new File(imagePath); if (mImage.exists()) { setResult(RESULT_OK); loadImage(mImage); } registerButtonCallbacks(); } @Override protected void onPause() { super.onPause(); } /** * Register callbacks for ui buttons */ protected void registerButtonCallbacks() { // Cancel button callback mCancel = (Button) findViewById(R.id.preview_send_cancel); mCancel.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { PreviewActivity.this.finish(); } }); // Confirm button callback mConfirm = (Button) findViewById(R.id.preview_send_confirm); mConfirm.setEnabled(true); mConfirm.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { new UploadImageTask().execute(mImage); } }); } /** * Initialize the dialogs */ @Override protected Dialog onCreateDialog(int id) { switch(id) { case UPLOAD_PROGRESS_DIALOG: mDialog = new ProgressDialog(this); mDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL); mDialog.setCancelable(false); mDialog.setTitle(getString(R.string.progress_dialog_title_connecting)); return mDialog; case UPLOAD_ERROR_DIALOG: AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setTitle(R.string.upload_error_title) .setIcon(android.R.drawable.ic_dialog_alert) .setMessage(R.string.upload_error_message) .setCancelable(false) .setPositiveButton(getString(R.string.retry), new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { PreviewActivity.this.finish(); } }); return builder.create(); case UPLOAD_SUCCESS_DIALOG: AlertDialog.Builder success = new AlertDialog.Builder(this); success.setTitle(R.string.upload_success_title) .setIcon(android.R.drawable.ic_dialog_info) .setMessage(R.string.upload_success_message) .setCancelable(false) .setPositiveButton(getString(R.string.success), new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { PreviewActivity.this.finish(); } }); return success.create(); default: return null; } } /** * Prepare the progress dialog */ @Override protected void onPrepareDialog(int id, Dialog dialog) { switch(id) { case UPLOAD_PROGRESS_DIALOG: mDialog.setProgress(0); mDialog.setTitle(getString(R.string.progress_dialog_title_connecting)); } } /** * Load the image file into the imageView * * @param image */ protected void loadImage(File image) { Bitmap bm = BitmapFactory.decodeFile(image.getPath()); ImageView view = (ImageView) findViewById(R.id.preview_image); view.setImageBitmap(bm); } /** * Asynchronous task to upload file to server */ class UploadImageTask extends AsyncTask<File, Integer, Boolean> { /** Upload file to this url */ private static final String UPLOAD_URL = "http://www.xxxx.x/xxxx/fotos"; /** Send the file with this form name */ private static final String FIELD_FILE = "file"; /** * Prepare activity before upload */ @Override protected void onPreExecute() { super.onPreExecute(); setProgressBarIndeterminateVisibility(true); mConfirm.setEnabled(false); mCancel.setEnabled(false); showDialog(UPLOAD_PROGRESS_DIALOG); } /** * Clean app state after upload is completed */ @Override protected void onPostExecute(Boolean result) { super.onPostExecute(result); setProgressBarIndeterminateVisibility(false); mConfirm.setEnabled(true); mDialog.dismiss(); if (result) { showDialog(UPLOAD_SUCCESS_DIALOG); } else { showDialog(UPLOAD_ERROR_DIALOG); } } @Override protected Boolean doInBackground(File... image) { return doFileUpload(image[0], "UPLOAD_URL"); } @Override protected void onProgressUpdate(Integer... values) { super.onProgressUpdate(values); if (values[0] == 0) { mDialog.setTitle(getString(R.string.progress_dialog_title_uploading)); } mDialog.setProgress(values[0]); } private boolean doFileUpload(File file, String uploadUrl) { HttpURLConnection connection = null; DataOutputStream outputStream = null; DataInputStream inputStream = null; String pathToOurFile = file.getPath(); String urlServer = "http://www.xxxx.x/xxxx/upload.php"; String lineEnd = "\r\n"; String twoHyphens = "--"; String boundary = "*****"; // log pathtoourfile Log.d("DFHinUpl", pathToOurFile); int bytesRead, bytesAvailable, bufferSize; byte[] buffer; int maxBufferSize = 1*1024*1024; int sentBytes = 0; long fileSize = file.length(); // log filesize String files= String.valueOf(fileSize); String buffers= String.valueOf(maxBufferSize); Log.d("fotosize",files); Log.d("buffers",buffers); try { FileInputStream fileInputStream = new FileInputStream(new File(pathToOurFile) ); URL url = new URL(urlServer); connection = (HttpURLConnection) url.openConnection(); // Allow Inputs & Outputs connection.setDoInput(true); connection.setDoOutput(true); connection.setUseCaches(false); // Enable POST method connection.setRequestMethod("POST"); connection.setRequestProperty("Connection", "Keep-Alive"); connection.setRequestProperty("Content-Type", "multipart/form-data;boundary="+boundary); outputStream = new DataOutputStream( connection.getOutputStream() ); outputStream.writeBytes(twoHyphens + boundary + lineEnd); outputStream.writeBytes("Content-Disposition: form-data; name=\"uploadedfile\";filename=\"" + pathToOurFile +"\"" + lineEnd); outputStream.writeBytes(lineEnd); bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); buffer = new byte[bufferSize]; // Read file bytesRead = fileInputStream.read(buffer, 0, bufferSize); while (bytesRead > 0) { outputStream.write(buffer, 0, bufferSize); bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); bytesRead = fileInputStream.read(buffer, 0, bufferSize); sentBytes += bufferSize; publishProgress((int)(sentBytes * 100 / fileSize)); bytesAvailable = fileInputStream.available(); bufferSize = Math.min(bytesAvailable, maxBufferSize); bytesRead = fileInputStream.read(buffer, 0, bufferSize); } outputStream.writeBytes(lineEnd); outputStream.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd); // Responses from the server (code and message) int serverResponseCode = connection.getResponseCode(); String serverResponseMessage = connection.getResponseMessage(); fileInputStream.close(); outputStream.flush(); outputStream.close(); try { int responseCode = connection.getResponseCode(); return responseCode == 200; } catch (IOException ioex) { Log.e("DFHUPLOAD", "Upload file failed: " + ioex.getMessage(), ioex); return false; } catch (Exception e) { Log.e("DFHUPLOAD", "Upload file failed: " + e.getMessage(), e); return false; } } catch (Exception ex) { String msg= ex.getMessage(); Log.d("DFHUPLOAD", msg); } return true; } } } the PHP code that handles this upload is following: <?php $date=getdate(); $urldate=$date['year'].$date['month'].$date['month'].$date['hours'].$date['minutes'].$date[ 'seconds']; $target_path = "./"; $target_path = $target_path . basename( $_FILES['uploadedfile']['name']) . $urldate; if(move_uploaded_file($_FILES['uploadedfile']['tmp_name'], $target_path)) { echo "The file ". basename( $_FILES['uploadedfile']['name']). " has been uploaded"; } else{ echo "There was an error uploading the file, please try again!"; } ?> would really appreciate it if someone could help me.

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  • WCF - (Custom) binary serialisation.

    - by Barguast
    I want to be able to query my database over the web, and I am wanting to use a WCF service to handle the requests and results. The problem is that due to the amount of data that can potentially be returned from these queries, I'm worried about how these results will be serialised over the network. For example, I can imagine the XML serialisation looking like: <Results> <Person Name="Adam" DateOfBirth="01/02/1985" /> <Person Name="Bob" DateOfBirth="04/07/1986" /> </Results> And the binary serialisation containing types names and other (unnecessary) metadata. Perhaps even the type name for each element in a collection? o_o Ideally, I'd like to perform the serialisation of certain 'DataContract'-s myself so I can make it super-compact. Does anyone know if this is possible, or of any articles which explain how to do custom serialisation with WCF? Thanks in advance

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  • API to Rank blog articles

    - by mnml
    I would like to know if there is any easy way to rank blog articles by counting how many times they have been retweeted / digg'ed / buzz'ed and if there is an existing api for it. The idea would be to keep important 'stories' at the top of the blog timeline.

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  • Too many open connections... Did I mess up something?

    - by Legend
    I am developing a plugin (for a Bittorrent client named Azureus programmed in Java) that lets me add peers into the current list from which it is downloading. Everything was working fine until yesterday when I started getting these weird errors: DEBUG::Thu Apr 15 10:45:40 CET 2010::org.gudy.azureus2.core3.peer.impl.control.PEPeerControlImpl::addPeer::795: Injected peer 90.35.126.126:33064 was not added - Too many connections DEBUG::Thu Apr 15 10:48:40 CET 2010::org.gudy.azureus2.core3.peer.impl.control.PEPeerControlImpl::addPeer::795: Injected peer 80.25.126.126:33064 was not added - Too many connections DEBUG::Thu Apr 15 10:52:40 CET 2010::org.gudy.azureus2.core3.peer.impl.control.PEPeerControlImpl::addPeer::795: Injected peer 90.35.126.126:33064 was not added - Too many connections I am thinking I messed up something with the TCP sockets. Does anyone know why this could be happening?

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  • Is Stream.Write thread-safe?

    - by Mike Spross
    I'm working on a client/server library for a legacy RPC implementation and was running into issues where the client would sometimes hang when waiting to a receive a response message to an RPC request message. It turns out the real problem was in my message framing code (I wasn't handling message boundaries correctly when reading data off the underlying NetworkStream), but it also made me suspicious of the code I was using to send data across the network, specifically in the case where the RPC server sends a large amount of data to a client as the result of a client RPC request. My send code uses a BinaryWriter to write a complete "message" to the underlying NetworkStream. The RPC protocol also implements a heartbeat algorithm, where the RPC server sends out PING messages every 15 seconds. The pings are sent out by a separate thread, so, at least in theory, a ping can be sent while the server is in the middle of streaming a large response back to a client. Suppose I have a Send method as follows, where stream is a NetworkStream: public void Send(Message message) { //Write the message to a temporary stream so we can send it all-at-once MemoryStream tempStream = new MemoryStream(); message.WriteToStream(tempStream); //Write the serialized message to the stream. //The BinaryWriter is a little redundant in this //simplified example, but here because //the production code uses it. byte[] data = tempStream.ToArray(); BinaryWriter bw = new BinaryWriter(stream); bw.Write(data, 0, data.Length); bw.Flush(); } So the question I have is, is the call to bw.Write (and by implication the call to the underlying Stream's Write method) atomic? That is, if a lengthy Write is still in progress on the sending thread, and the heartbeat thread kicks in and sends a PING message, will that thread block until the original Write call finishes, or do I have to add explicit synchronization to the Send method to prevent the two Send calls from clobbering the stream?

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  • Can Bonjour browse a service with a particular name?

    - by Roman
    Bonjour provides "DNSSD.browse(serviceType,callBackObject)" method which browses for services of a particular type. If a service of the given type is found, Bonjour call "callBackObject.serviceFound". If the service is lost, Bonjour calls "callBackObject.serviceLost". I alway considered "DNSSD.browse" as a method for monitoring a particular service. Bonjour monitors a particular service and calls necessary method if the service is found (available) or lost (not available). But than I realized that "DNSSD.browse" receives (as argument) a type of service (for example "http.tcp") and there can be several services of this type. So, its probably calls "serviceFound" and "serviceLost" if any service of the specified type is found or lost, respectively. But in my application I would like to browse just for one particular service. What is the best way to do it? I have two potential solutions: When I register a service, I give it a unique type. For example: "server1.http.tcp". I register services with unique names (not types) and ask Bonjour to browse for services with particular names. But I am not sure that Bonjour provide such possibility. Can it browse for services with specific names?

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  • How do you get the ethernet address using Java?

    - by Frank Krueger
    I would like to retrieve the ethernet address of the network interface that is used to access a particular website. How can this be done in Java? Solution Note that the accepted solution of getHardwareAddress is only available in Java 6. There does not seem to be a solution for Java 5 aside from executing i(f|p)confing.

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  • iPhone - How do I find the MAC address of the connected WiFi access point?

    - by Ciaran
    Without using the private APIs, is it possible to programatically determine the MAC address of the access point that the iPhone is connected to? I understand that this should be doable using the core BSD libraries, but we are new to this, so it would be great if someone can point us to some starter code. Note: we're trying to determine the MAC address of the remote device - not the MAC address of the iPhone.

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  • Compare Quagga to XORP

    - by Sargun Dhillon
    What do you think of Quagga compared to XORP as a dynamic software routing engine? What are the technical merits of each engine comparatively? Additionally, what do most people think of them from a programming view. Who has manipulated networks using these enginers? I was wondering from an OSPF, routing, BGP protocol user's perpspective.

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  • Programatically determining maximum transfer rate

    - by dauphic
    I have a problem that requires me to calculate the maximum upload and download available, then limit my program's usage to a percentage of it. However, I can't think of a good way to find the maximums. At the moment, the only solution I can come up with is transfering a few megabytes between the client and server, then measuring how ling the transfer took. This solution is very undesirable, however, because with 100,000 clients it could potentially result in too much of an increase to our server's bandwidth usage (which is already too high). Does anyone have any solutions to this problem?

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  • Accessing mapped network drive from ColdFusion

    - by Kip
    I am having a problem accessing a mapped drive in ColdFusion. I have \\server\files\sharing mapped to z:\. If I run this code, it says the directory exists for the full path but not for the mapped one: <cfscript> fullPath = "\\server\files\sharing\reports"; mappedPath = "z:\reports"; WriteOutput("fullPath exists: #DirectoryExists(fullPath)#<br/>"); //YES WriteOutput("mappedPath exists: #DirectoryExists(mappedPath)#"); //NO </cfscript> I have done some Googling and have found a few people with the same problem, but the solution was always to use the full path. Is there a reason ColdFusion wouldn't be able to see or access the mapped drive? And if so, are there any workarounds (maybe a system call to get the full path of the mapped drive)?

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  • Socket.Recieve Failing When Multithreaded

    - by Qua
    The following piece of code runs fine when parallelized to 4-5 threads, but starts to fail as the number of threads increase somewhere beyond 10 concurrentthreads int totalRecieved = 0; int recieved; StringBuilder contentSB = new StringBuilder(4000); while ((recieved = socket.Receive(buffer, SocketFlags.None)) > 0) { contentSB.Append(Encoding.ASCII.GetString(buffer, 0, recieved)); totalRecieved += recieved; } The Recieve method returns with zero bytes read, and if I continue calling the recieve method then I eventually get a 'An established connection was aborted by the software in your host machine'-exception. So I'm assuming that the host actually sent data and then closed the connection, but for some reason I never recieved it. I'm curious as to why this problem arises when there are a lot of threads. I'm thinking it must have something to do with the fact that each thread doesn't get as much execution time and therefore there are some idle time for the threads which causes this error. Just can't figure out why idle time would cause the socket not to recieve any data.

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  • Network Security and Encryption explained in laymen terms

    - by Ehrann Mehdan
    Although I might pretend very well that I known a thing about networks or security and it might help me pass an interview, or fix a bug, I don't really feel I'm fooling anyone. I'm looking for a laymen terms explanation of nowadays network security concepts and solutions. The information is scattered around and I didn't find a resource for "dummies" like me (e.g experienced Java developers that can speak the jargon but have no real clue what it means) Topics I have a weak notion about and want to understand better as a Java developer PGP Public / Private keys RSA / DES SSL and 2 way SSL (keystore / trustore) Protecting against Man in the middle fraud Digital Signature and Certificates Is there a resource out there that really explains it in a way that doesn't require a Cisco certificate / Linux lingo / know what is subnet masking or other plumbing skills?

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  • Using Boost.Asio to get "the whole packet"

    - by wowus
    I have a TCP client connecting to my server which is sending raw data packets. How, using Boost.Asio, can I get the "whole" packet every time (asynchronously, of course)? Assume these packets can be any size up to the full size of my memory. Basically, I want to avoid creating a statically sized buffer.

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