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  • Image Upload directly from client to remote server? Spring/Tomcat

    - by Prem
    Just wondering what the common solution is for this. We have two web servers that are load balanced and a separate server that holds our images. Our current process is that a user uploads an image directly to the web server (which ever they are connected to) and we enter a job into our DB. Another process checks for image jobs every few mins and copies the image from the web server up to the image server. The delay from when a user uploads to when its visible is not ideal. We could tighten the loop on how often we check for image jobs but ideally I would like to have user uploaded images to go directly to the image server rather than copying twice. How should this be done? Is there anything in spring to deal with this ? Seems like how most would deal with a CDN i would think? I want to limit the time it takes for an image that a user uploads is available on our site...

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  • Code only runs properly if debugging step-by-step

    - by Cornwell
    Hello, I'm making a webserver and I've come up with some very strange problems. My server was running as expected yesterday when I turned off my laptop, but today it only sends the http headers (I didn't change anything) When a user requests a file, if I send them using the following code, it works perfectly: while ((n = fread(data, 1, sizeof(data), file)) > 0) send(ts, data, n, 0); but if I change it to this, it only sends ~2% of the file. And that's not a random number, it actually only sends about 2% of the file. while ((n = fread(data, 1, sizeof(data), file)) > 0) web.Send(data); int WEB::Send(string data) { return send(TempSocket, data.c_str(), data.size(), 0); } changing string to char* doesn't solve the problem. I'm using visual studio2010. If I run my code step-by-step, I am able to solve problem #1, everything gets sent. And that is my main problem. I do not understand why it happens. Hopefully someone can explain it to me. Thanks in advance. EDIT: int APIENTRY WinMain( HINSTANCE hInstance, HINSTANCE hPrev, LPSTR lpCmd,int nShow) { SOCKET MainSocket=0; MSG msg; RedirectIOToConsole(); CreateThread(NULL, NULL, ListenThread, NULL, NULL, NULL); while (GetMessage(&msg, NULL, 0, 0)) { TranslateMessage(&msg); DispatchMessage(&msg); } WSACleanup(); closesocket(MainSocket); MainSocket = INVALID_SOCKET; return msg.wParam; } DWORD WINAPI ListenThread(LPVOID lparam) { SOCKET MainSocket; WSADATA wsaData; SOCKET tmpsock; struct sockaddr_in local, from; int fromlen=sizeof(from); WSAStartup(MAKEWORD(2, 2), &wsaData); local.sin_family=AF_INET; local.sin_addr.s_addr=INADDR_ANY; local.sin_port=htons(PORT); MainSocket=socket(AF_INET,SOCK_STREAM,0); if(MainSocket==INVALID_SOCKET) { return 0; } if(bind(MainSocket,(struct sockaddr*)&local,sizeof(local))!=0) { return 0; } if(listen(MainSocket,10)!=0) { return 0; } while(1) { tmpsock = accept(MainSocket,(struct sockaddr*)&from,&fromlen); CreateThread(NULL, NULL, SlaveThread, (LPVOID)tmpsock, NULL, NULL); } } DWORD WINAPI SlaveThread(LPVOID lparam) { SOCKET ts = (SOCKET)lparam;//temporary socket ...... char data[4096]; int n; unsigned long int length = statbuf.st_size; web.SendHeaders(200, "OK", format("Content-Disposition: attachment; filename=\"%s\"", FileName.c_str()).c_str(), web.GetMimeType(ReqPath.c_str()), length, statbuf.st_mtime); unsigned long int i=0,d=0; while ((n = fread(data, 1, sizeof(data), file)) > 0) { d+=send(ts, data, n, 0); i+=n; } printf("%i=%i=%i\n", length,i,d); fclose(file);

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  • Server-side access to Client Browser's Latitude/Longitude using Django.

    - by ZenGyro
    Hello, So i am writing a little app that compares a user's position against a database on web-based server written using Django and performs some functions with it. Accessing the browser's geolocation data (in supported browsers ) is fairly trivial using JavaScript. But what is the best way to allow the Django server to access the longitude and latitude variables? Is it best to wrap them up as a JSON object and send to the server via POST? Or is there some easier (Geo)Django-based way to access the Navigator.geolocation browser object. Please forgive a newbie a question like this, but my Google-Fuing only seems to find ways to insert variables into JavaScript via template tag, whereas I need it to work the other way! Any advice or code snippets greatly appreciated. Feel free to talk to me like I am an idiot.

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  • Multi-client C# ODBC (Sybase/Oracle/MSSQL) table access question.

    - by Hamish Grubijan
    I am working on a feature that would allow clients pick a unique identifier (ci_name). The code below is a generic version that gets expanded to the right sql depending on the vendor. Hopefully it makes sense. #include "sql.h" create table client_identification ( ci_id TYPE_ID IDENTITY, ci_name varchar(64) not null, constraint ci_pk primary key (ci_name) ); go CREATE_SEQUENCE(ci_id) There will be simple stored procedures for adding, retrieving, and deleting these user records. This will be used by several admins. This will not happen very frequently, but there is still a possibility that something will be added or deleted since the list was initially retrieved. I have not yet decided if I need to detect the case of a double delete, but the user name cannot be created twice - primary key constraint will object. I want to be able to detect this particular case and display something like: "you snooze - you loose." :) I would like to leverage the pk constraint instead of doing some extra sql gymnastics. So, how can I detect this case cleanly, so that it works in MS SQL 2008, Sybase, and Oracle? I hope to do better than catch a general ODBC exception and parse out the text and look for what Sybase, Oracle, and MSSQL would give me back. Oracle is a little different. We actually prepend these variables to the Oracle version of stored procedures because they are not available otherwise: Vret_val out number, Vtran_count in out number, Vmessage_count in out number, Thanks. General helpful tips and comments are welcome, except for naming convention ones ( I do not have a choice here, plus I mangled the actual names a bit).

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  • saving dataset in excel and allow user to download it in the client machine.

    - by Jebli
    Hi, I am developing an application where i want i am displaying a dataset in the datagrid view for the user.Now the user wants to download the data in the datagridview in an excel format.How can i do it ? 1) should i write the dataset in the excel and save it the server before the user download the file ? 2) Can i use a hyper link and set the path of the file that is saved in the server to the hyper link hRef property , so that the user can click and download the file ? I am using C# ASP.net 2.0 Please help !

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  • Splitting Code into Headers/Source files

    - by cam
    I took the following code from the examples page on Asio class tcp_connection : public boost::enable_shared_from_this<tcp_connection> { public: typedef boost::shared_ptr<tcp_connection> pointer; static pointer create(boost::asio::io_service& io_service) { return pointer(new tcp_connection(io_service)); } tcp::socket& socket() { return socket_; } void start() { message_ = make_daytime_string(); boost::asio::async_write(socket_, boost::asio::buffer(message_), boost::bind(&tcp_connection::handle_write, shared_from_this(), boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } private: tcp_connection(boost::asio::io_service& io_service) : socket_(io_service) { } void handle_write(const boost::system::error_code& /*error*/, size_t /*bytes_transferred*/) { } tcp::socket socket_; std::string message_; }; I'm relatively new to C++ (from a C# background), and from what I understand, most people would split this into header and source files (declaration/implementation, respectively). Is there any reason I can't just leave it in the header file if I'm going to use it across many source files? If so, are there any tools that will automatically convert it to declaration/implementation for me? Can someone show me what this would look like split into header/source file for an example (or just part of it, anyway)? I get confused around weird stuff like thistypedef boost::shared_ptr<tcp_connection> pointer; Do I include this in the header or the source? Same with tcp::socket& socket() I've read many tutorials, but this has always been something that has confused me about C++.

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  • alert to back office personnel on client side trigerring?

    - by ZX12R
    I am building a ruby on rails project. it is a portal. I have a situation as follows: the user browses around. Suddenly he gets a doubt. I want to keep a small text box and a button that says "call me". To clarify the doubt the user can enter his phone number in the "call me" box. now the back office personnel should get an alert or a notification about this. I tried implementing juggernaut, but became a nightmare since the site is in a shared host and i couldn't configure the port. Kindly suggest a solution.

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  • C++ MFC server app with sockets crashes and I cannot find the fault, help!

    - by usermeister
    My program has one dialog and two sockets. Both sockets are derived from CAsyncSocket, one is for listening, other is for receiving data from client. My program crashes when client tries to connect to server application and server needs to initialize receiving socket. This is my MFC dialog class. class CFileTransferServerDlg : public CDialog { ... ListeningSocket ListenSock; ReceivingSocket* RecvSock; void OnAccept(); // called when ListenSock gets connection attempt ... }; This is my derived socket class for receiving data that calls parent dialogs method when event is signaled. class ReceivingSocket : public CAsyncSocket { CFileTransferServerDlg* m_pDlg; // for accessing parent dialogs controls virtual void OnReceive(int nErrorCode); } ReceivingSocket::ReceivingSocket() { } This is dialogs function that handles incoming connection attempt when listening socket gets event notification. This is where the crash happens. void CFileTransferServerDlg::OnAccept() { RecvSock = new ReceivingSocket; /* CRASH */ } OR void CFileTransferServerDlg::OnAccept() { ReceivingSocket* tmpSock = new ReceivingSocket; tmpSock->SetParentDlg(this); CString message; if( ListenSock.Accept(*tmpSock) ) /* CRASH */ { message.LoadStringW(IDS_CLIENT_CONNECTED); m_txtStatus.SetWindowTextW(message); RecvSock = tmpSock; } } My program crashes when I try to create a socket for receiving file sent from client application. OnAccept starts when Listening socket signals incoming connection attempt, but my application then crashes. I've tried running it on another computer and connection attempt was succesful. What could be wrong? Error in debug mode: Unhandled exception at 0x009c30e1 in FileTransferServer.exe: 0xC0000005: Access violation reading location 0xccccce58.

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  • What prevents a user from adding controls to an ASP.NET page client side?

    - by Curtis White
    This goes back to my other question which I thought was sufficiently answers but upon reflect am not sure that it was (sorry). Backgrounder: I am generating a form dynamically. I am pulling from the database the controls. I must associate each control with a database ID which is not the user's session id. I do this currently by storing my ID in the ID for the web control with some other stuff to make it unique/clear what I am doing. On the post back, I iterate through all the controls on my web page checking for my special identifier, ie, MyGeneratedTextBox_ID_Unique. This process enables for 2 important steps, identifying the control was one I generated and also getting the ID for this input field. And, all of this works but I'm still concerned about the security of it. I do not see a security issue with showing the actual database ID's in this case, although agree it is not desirable. However, I am concerned of the following possibilities: If a user could add a nefarious control to my collection and use that for a SQL injection attack. More academic, but if a user could somehow store data for fields they do not have access too by changing the id's. I agree this is a "hack" of a way to do it. But my question is, is it a security risk and is there an 'easy' way to do it in a less hack way? I assume that only the controls that are created/instantiated on the page are added to the controls list.. thus all controls must be created server side and thus the security issue is address but just wanted to validate. Thanks again. PS: I could see adding a property for each control and encrypting the viewstate would be a little more secure.

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  • Where to begin with multi-threaded programming with c++?

    - by zoke
    I'm trying to implement my own IRC client as a personal proejct and I realized I needed a way to read and write from the socket at the same time. I realized I could have a reading thread which reads from the socket in the background and puts data in a queue and I could have another thread which writes data from a queue to the socket. However I have no idea on how to start with multithreaded programing or how to do it with c++. Where do I go from here?

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  • How Do Sockets Work in C?

    - by kaybenleroll
    I am a bit confused about socket programming in C. You create a socket, bind it to an interface and an IP address and get it to listen. I found a couple of web resources on that, and understood it fine. In particular, I found an article Network programming under Unix systems to be very informative. What confuses me is the timing of data arriving on the socket. How can you tell when packets arrive, and how big the packet is, do you have to do all the heavy lifting yourself? My basic assumption here is that packets can be of variable length, so once binary data starts appearing down the socket, how do you begin to construct packets from that?

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  • How do you get the client size in a Silverlight Application?

    - by Stefan
    I want to get the size of the browser window running my Silverlight Application? I've tried the following lines, but it always returns zero! public Page() { InitializeComponent(); Initialize(); } public void Initialize() { WorldLimits.Y = Application.Current.Host.Content.ActualHeight; WorldLimits.X = Application.Current.Host.Content.ActualWidth; gameCore = new GameCore(this); gameTime = DateTime.Now.TimeOfDay.TotalMilliseconds / 1000; }

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  • Server sends json data correctly. Client parses it wrong

    - by alois.wirkes
    I have a PHP code that generates a JSON string to send to my Android app. This part works. The problem is when my app captures that string and try to convert it into a JSONArray object. The main idea is to store that data inside a SQLite database. Here's the code that captures the JSON string: public void getPostResponse(){ try{ br = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8); sb = new StringBuilder(); line = null; while((line = br.readLine()) != null){ sb.append(line+"\n"); } is.close(); result = sb.toString(); Log.e("getPostResponse","result= "+sb.toString()); }catch(Exception e){ Log.e("log_tag","Error converting result "+e.toString()); } } And this is the result in the LogCat: 10-11 16:27:01.171: E/getPostResponse(9155): result= [{ "establecimientos":[]},{ "rutas":[]},{ "formularios":[]},{ "clientes":[]},{ "mediciones":[]}] This is why I think there's an error, the result variable should contain the whole JSON string and it doesn't. Any ideas? Variables br, sb, line and result are declared globally. JSON sent from server is already a JSONArray (starts with '[' and ends with ']'), is this what's causing the problem?

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  • What in-client caching options work well with Cassandra and Java?

    - by sanity
    I'm currently architecting a system that must be capable of dealing with tens of thousands of writes per second. I am more-or-less settled on using Apache Cassandra for the persistence layer, and will be using Java for the application layer, but there are situations where I need to quickly access data in a way that picks up any changes within seconds. Hitting Cassandra every single time I need to check this data for changes will be too slow, which means I need to use some kind of application layer caching. To ensure that the cached data remains current, ideally it would support some kind of multicast-based cache invalidation. What are my options?

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  • why does my C# client that uses Library A need to have a using statement for Library B (which A uses

    - by Greg
    Hi, I have: Main Program Class - uses Library A Library A - has partial classes which mix in methods from Library B Library B - mix in methods & interfaces So in Library B when I include a partial Node class which implements INode (defined in Library B) I suddenly get an error in my main class where it uses Node from Library A. The error tells me in the Main Class I have to have a using statement to Library B. Any ideas?

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  • How to enforce that HTTP client uses conditional requests for updates?

    - by Day
    In a (proper RMM level 3) RESTful HTTP API, I want to enforce the fact that clients should make conditional requests when updating resources, in order to avoid the lost update problem. What would be an appropriate response to return to clients that incorrectly attempt unconditional PUT requests? I note that the (abandoned?) mod_atom returns a 405 Method Not Allowed with an Allow header set to GET, HEAD (view source) when an unconditional update is attempted. This seems slightly misleading - to me this implies that PUT is never a valid method to attempt on the resource. Perhaps the response just needs to have an entity body explaining that If-Match or If-Unmodified-Since must be used to make the PUT request conditional in which case it would be allowed? Or perhaps a 400 Bad Request with a suitable explanation in the entity body would be a better solution? But again, this doesn't feel quite right because it's using a 400 response for a violation of application specific semantics when RFC 2616 says (my emphasis): The request could not be understood by the server due to malformed syntax. But than again, I think that using 400 Bad Request for application specific semantics is becoming a widely accepted pragmatic solution (citation needed!), and I'm just being overly pedantic.

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  • What is the best way to implement a Server-Client connection between an iPad and multiple iPhones?

    - by Infinite
    Based on a college-project I'm trying to realize a relatively simple game (Poker) where an iPad acts as Server and multiple iPod-Touchs connect to it as Clients. Gamekit seems to drop out, since those old ipod-touch-devices don't have bluetooth-support. Are there already some Frameworks out there simplifying the process, or do I have to fall back on TCP-Streaming-Sockets and implement it myself?

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  • Problems with Asynchronous UDP Sockets

    - by ihatenetworkcoding
    Hi, I'm struggling a bit with socket programming (something I'm not at all familiar with) and I can't find anything which helps from google or MSDN (awful). Apologies for the length of this. Basically I have an existing service which recieves and responds to requests over UDP. I can't change this at all. I also have a client within my webapp which dispatches and listens for responses to that service. The existing client I've been given is a singleton which creates a socket and an array of response slots, and then creates a background thread with an infinite looping method that makes "sock.Receive()" calls and pushes the data received into the slot array. All kinds of things about this seem wrong to me and the infinite thread breaks my unit testing so I'm trying to replace this service with one which makes it's it's send/receives asynchronously instead. Point 1: Is this the right approach? I want a non-blocking, scalable, thread-safe service. My first attempt is roughly like this, which sort of worked but the data I got back was always shorter than expected (i.e. the buffer did not have the number of bytes requested) and seemed to throw exceptions when processed. private Socket MyPreConfiguredSocket; public object Query() { //build a request this.MyPreConfiguredSocket.SendTo(MYREQUEST, packet.Length, SocketFlags.Multicast, this._target); IAsyncResult h = this._sock.BeginReceiveFrom(response, 0, BUFFER_SIZE, SocketFlags.None, ref this._target, new AsyncCallback(ARecieve), this._sock); if (!h.AsyncWaitHandle.WaitOne(TIMEOUT)) { throw new Exception("Timed out"); } //process response data (always shortened) } private void ARecieve (IAsyncResult result) { int bytesreceived = (result as Socket).EndReceiveFrom(result, ref this._target); } My second attempt was based on more google trawling and this recursive pattern I frequently saw, but this version always times out! It never gets to ARecieve. public object Query() { //build a request this.MyPreConfiguredSocket.SendTo(MYREQUEST, packet.Length, SocketFlags.Multicast, this._target); State s = new State(this.MyPreConfiguredSocket); this.MyPreConfiguredSocket.BeginReceiveFrom(s.Buffer, 0, BUFFER_SIZE, SocketFlags.None, ref this._target, new AsyncCallback(ARecieve), s); if (!s.Flag.WaitOne(10000)) { throw new Exception("Timed out"); } //always thrown //process response data } private void ARecieve (IAsyncResult result) { //never gets here! State s = (result as State); int bytesreceived = s.Sock.EndReceiveFrom(result, ref this._target); if (bytesreceived > 0) { s.Received += bytesreceived; this._sock.BeginReceiveFrom(s.Buffer, s.Received, BUFFER_SIZE, SocketFlags.None, ref this._target, new AsyncCallback(ARecieve), s); } else { s.Flag.Set(); } } private class State { public State(Socket sock) { this._sock = sock; this._buffer = new byte[BUFFER_SIZE]; this._buffer.Initialize(); } public Socket Sock; public byte[] Buffer; public ManualResetEvent Flag = new ManualResetEvent(false); public int Received = 0; } Point 2: So clearly I'm getting something quite wrong. Point 3: I'm not sure if I'm going about this right. How does the data coming from the remote service even get to the right listening thread? Do I need to create a socket per request? Out of my comfort zone here. Need help.

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  • Detecting TCP dropout over an unreliable network

    - by yx
    I am doing some experimentation over an unreliable radio network (home brewed) using very rudimentary java socket programming to transfer messages back and forth between the end nodes. The setup is as follows: Node A --- Relay Node --- Node B One problem I am constantly running into is that somehow the connection drops out and neither Node A or B knows that the link is dead, and yet continues to transmit data. The TCP connection does not time out either. I have added in a heartbeat message that causes a timeout after a while, but I still would like to know what is the underlying cause of why TCP does not time out. Here are the options I am enabling when setting up a socket: channel.socket().setKeepAlive(false); channel.socket().setTrafficClass(0x08); // for max throughput This behavior is strange since it is totally different than when I have a wired network. On a wired network, I can simulate a disconnected connection by pulling out the ethernet cord, however, once I plug the cord back in, the connection becomes restablished and messages begin to be passed through once more. On the radio network, the connection is never reestablished and once it silently dies, the messages never resume. Is there some other unknown java implentation or setting for a socket that I can use, also, why am I seeing this behavior in the first place? And yes, before anyone says anything, I know TCP is not the preffered choice over an unreliable network, but in this case I wanted to ensure no packet loss.

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