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  • I don't understand how work call_once

    - by SABROG
    Please help me understand how work call_once Here is thread-safe code. I don't understand why this need Thread Local Storage and global_epoch variables. Variable _fast_pthread_once_per_thread_epoch can be changed to constant/enum like {FAST_PTHREAD_ONCE_INIT, BEING_INITIALIZED, FINISH_INITIALIZED}. Why needed count calls in global_epoch? I think this code can be rewriting with logc: if flag FINISH_INITIALIZED do nothing, else go to block with mutexes and this all. #ifndef FAST_PTHREAD_ONCE_H #define FAST_PTHREAD_ONCE_H #include #include typedef sig_atomic_t fast_pthread_once_t; #define FAST_PTHREAD_ONCE_INIT SIG_ATOMIC_MAX extern __thread fast_pthread_once_t _fast_pthread_once_per_thread_epoch; #ifdef __cplusplus extern "C" { #endif extern void fast_pthread_once( pthread_once_t *once, void (*func)(void) ); inline static void fast_pthread_once_inline( fast_pthread_once_t *once, void (*func)(void) ) { fast_pthread_once_t x = *once; /* unprotected access */ if ( x _fast_pthread_once_per_thread_epoch ) { fast_pthread_once( once, func ); } } #ifdef __cplusplus } #endif #endif FAST_PTHREAD_ONCE_H Source fast_pthread_once.c The source is written in C. The lines of the primary function are numbered for reference in the subsequent correctness argument. #include "fast_pthread_once.h" #include static pthread_mutex_t mu = PTHREAD_MUTEX_INITIALIZER; /* protects global_epoch and all fast_pthread_once_t writes */ static pthread_cond_t cv = PTHREAD_COND_INITIALIZER; /* signalled whenever a fast_pthread_once_t is finalized */ #define BEING_INITIALIZED (FAST_PTHREAD_ONCE_INIT - 1) static fast_pthread_once_t global_epoch = 0; /* under mu */ __thread fast_pthread_once_t _fast_pthread_once_per_thread_epoch; static void check( int x ) { if ( x == 0 ) abort(); } void fast_pthread_once( fast_pthread_once_t *once, void (*func)(void) ) { /*01*/ fast_pthread_once_t x = *once; /* unprotected access */ /*02*/ if ( x _fast_pthread_once_per_thread_epoch ) { /*03*/ check( pthread_mutex_lock(µ) == 0 ); /*04*/ if ( *once == FAST_PTHREAD_ONCE_INIT ) { /*05*/ *once = BEING_INITIALIZED; /*06*/ check( pthread_mutex_unlock(µ) == 0 ); /*07*/ (*func)(); /*08*/ check( pthread_mutex_lock(µ) == 0 ); /*09*/ global_epoch++; /*10*/ *once = global_epoch; /*11*/ check( pthread_cond_broadcast(&cv;) == 0 ); /*12*/ } else { /*13*/ while ( *once == BEING_INITIALIZED ) { /*14*/ check( pthread_cond_wait(&cv;, µ) == 0 ); /*15*/ } /*16*/ } /*17*/ _fast_pthread_once_per_thread_epoch = global_epoch; /*18*/ check (pthread_mutex_unlock(µ) == 0); } } This code from BOOST: #ifndef BOOST_THREAD_PTHREAD_ONCE_HPP #define BOOST_THREAD_PTHREAD_ONCE_HPP // once.hpp // // (C) Copyright 2007-8 Anthony Williams // // Distributed under the Boost Software License, Version 1.0. (See // accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) #include #include #include #include "pthread_mutex_scoped_lock.hpp" #include #include #include namespace boost { struct once_flag { boost::uintmax_t epoch; }; namespace detail { BOOST_THREAD_DECL boost::uintmax_t& get_once_per_thread_epoch(); BOOST_THREAD_DECL extern boost::uintmax_t once_global_epoch; BOOST_THREAD_DECL extern pthread_mutex_t once_epoch_mutex; BOOST_THREAD_DECL extern pthread_cond_t once_epoch_cv; } #define BOOST_ONCE_INITIAL_FLAG_VALUE 0 #define BOOST_ONCE_INIT {BOOST_ONCE_INITIAL_FLAG_VALUE} // Based on Mike Burrows fast_pthread_once algorithm as described in // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2444.html template void call_once(once_flag& flag,Function f) { static boost::uintmax_t const uninitialized_flag=BOOST_ONCE_INITIAL_FLAG_VALUE; static boost::uintmax_t const being_initialized=uninitialized_flag+1; boost::uintmax_t const epoch=flag.epoch; boost::uintmax_t& this_thread_epoch=detail::get_once_per_thread_epoch(); if(epoch #endif I right understand, boost don't use atomic operation, so code from boost not thread-safe?

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  • Practices for Foreground/Background threads in .NET

    - by Andrei Taptunov
    I work with in-house legacy communication framework which exposes some high level abstractions. These abstractions are wrappers with some logic around .NET threads. When I looked at code I've noticed that some abstractions are wrappers around foreground threads while others are wrappers around background threads. The sad thing is that I don't see any logic why in some cases foreground threads are used and background in other cases. Are there any guidelines or patterns & practices when it's better to choose one over another on server side and client side (I believe there should be some difference)?

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  • Measuring Programmers' Productivity. Bad, good or invasive?

    - by Fraga
    A client needs my company to develop an app that will be able to measure the programmer productivity, by getting information from VS, IE, SSMS, profiler and VMware. For example: Lines, Methods, Classes (Added, Deleted, Modified) How many time spent in certain file, class, method, specific task, etc. How many time in different stages of the development cycle (Design, Coding, Debugging, Compiling, Testing) Real lines of code. Etc They told me they want to implement PSP. Would you resign if a company wants to measure this way? OR Would you install this kind of software for self improvement?

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  • Quantum PSO and Charged PSO (PSO = Particle Swarm Optimizer)

    - by The Elite Gentleman
    Hi Guys I need to implement PSO's (namely charged and quantum PSO's). My questions are these: What Velocity Update strategy do each PSO's use (Synchronous or Asynchronous particle update) What social networking topology does each of the PSO's use (Von Neumann, Ring, Star, Wheel, Pyramid, Four Clusters) For now, these are my issues. All your help will be appreciated. Thanks.

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  • Openerp WIth ubuntu 9.04

    - by agbrand
    I had Ubuntu 8.10. I upgrade it to 9.04. I have Openerp5.0 , server/client/web. It worked on 8.10 but not with 9.04. Now when I try to launch my server using: ./openerp-server.py I have this error: ERROR: Import xpath module ERROR: Try to install the old python-xml package It seems that this version of openerp doesn't work with python2.6. Can you help me to redirect openerp to use old version of python please?

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  • How to determine if an application is using the GPU

    - by Andrew
    I'm looking for a way to determine how to know whether an application is using the GPU with Objective-C. I want to be able to determine if any applications currently running on the system have work going on on the GPU (ie: a reason why the latest MacBook Pros would switch to the discrete graphics over the Intel HD graphics). I've tried getting the information by crossing the list of active windows with the list of windows that have their backing location stored in video memory using Quartz Window Services, but all that does is return the Dock application and I have other applications open that I know are using the GPU (Photoshop CS5, Interface Builder), that and the Dock doesn't require the 330m.

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  • How can I use functools.partial on multiple methods on an object, and freeze parameters out of order

    - by Joseph Garvin
    I find functools.partial to be extremely useful, but I would like to be able to freeze arguments out of order (the argument you want to freeze is not always the first one) and I'd like to be able to apply it to several methods on a class at once, to make a proxy object that has the same methods as the underlying object except with some of its methods parameter being frozen (think of it as generalizing partial to apply to classes). I've managed to scrap together a version of functools.partial called 'bind' that lets me specify parameters out of order by passing them by keyword argument. That part works: >>> def foo(x, y): ... print x, y ... >>> bar = bind(foo, y=3) >>> bar(2) 2 3 But my proxy class does not work, and I'm not sure why: >>> class Foo(object): ... def bar(self, x, y): ... print x, y ... >>> a = Foo() >>> b = PureProxy(a, bar=bind(Foo.bar, y=3)) >>> b.bar(2) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: bar() takes exactly 3 arguments (2 given) I'm probably doing this all sorts of wrong because I'm just going by what I've pieced together from random documentation, blogs, and running dir() on all the pieces. Suggestions both on how to make this work and better ways to implement it would be appreciated ;) One detail I'm unsure about is how this should all interact with descriptors. Code follows. from types import MethodType class PureProxy(object): def __init__(self, underlying, **substitutions): self.underlying = underlying for name in substitutions: subst_attr = substitutions[name] if hasattr(subst_attr, "underlying"): setattr(self, name, MethodType(subst_attr, self, PureProxy)) def __getattribute__(self, name): return getattr(object.__getattribute__(self, "underlying"), name) def bind(f, *args, **kwargs): """ Lets you freeze arguments of a function be certain values. Unlike functools.partial, you can freeze arguments by name, which has the bonus of letting you freeze them out of order. args will be treated just like partial, but kwargs will properly take into account if you are specifying a regular argument by name. """ argspec = inspect.getargspec(f) argdict = copy(kwargs) if hasattr(f, "im_func"): f = f.im_func args_idx = 0 for arg in argspec.args: if args_idx >= len(args): break argdict[arg] = args[args_idx] args_idx += 1 num_plugged = args_idx def new_func(*inner_args, **inner_kwargs): args_idx = 0 for arg in argspec.args[num_plugged:]: if arg in argdict: continue if args_idx >= len(inner_args): # We can't raise an error here because some remaining arguments # may have been passed in by keyword. break argdict[arg] = inner_args[args_idx] args_idx += 1 f(**dict(argdict, **inner_kwargs)) new_func.underlying = f return new_func

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  • Delphi On Windows

    - by j-t-s
    Hi All I have decided (whether it's for better or for worse), to start learning Delphi. But, Is it available in Visual Studio? Or is there an IDE for it? I googled Delphi, but came up with some really weird sites. Thanks Jason

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  • Parallel computing for integrals

    - by Iman
    I want to reduce the calculation time for a time-consuming integral by splitting the integration range. I'm using C++, Windows, and a quad-core Intel i7 CPU. How can I split it into 4 parallel computations?

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  • seperating interface and implemention with normal functions

    - by ace
    this seems like it should be pretty simple, im probably leaving something simple out. this is the code im trying to run. it is 3 files, 2*cpp and 1*header. -------------lab6.h ifndef LAB6_H_INCLUDED define LAB6_H_INCLUDED int const arraySize = 10; int array1[arraySize]; int array2[arraySize]; void generateArray(int[], int ); void displayArray(int[], int[], int ); void reverseOrder(int [],int [], int); endif // LAB6_H_INCLUDED -----------------lab6.cpp include using std::cout; using std::endl; include using std::rand; using std::srand; include using std::time; include using std::setw; include "lab6.h" void generateArray(int array1[], int arraySize) { srand(time(0)); for (int i=0; i<10; i++) { array1[i]=(rand()%10); } } void displayArray(int array1[], int array2[], int arraySize) { cout<<endl<<"Array 1"<<endl; for (int i=0; i<arraySize; i++) { cout<<array1[i]<<", "; } cout<<endl<<"Array 2"<<endl; for (int i=0; i<arraySize; i++) { cout<<array2[i]<<", "; } } void reverseOrder(int array1[],int array2[], int arraySize) { for (int i=0, j=arraySize-1; i<arraySize;j--, i++) { array2[j] = array1[i]; } } ------------and finally main.cpp include "lab6.h" int main() { generateArray(array1, arraySize); reverseOrder(array1, array2, arraySize); displayArray(array1, array2, arraySize); return 0; }

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  • How to File Transfer client to Server?

    - by Phsika
    i try to recieve a file from server but give me error on server.Start() ERROR : In a manner not permitted by the access permissions to access a socket was attempted to How can i solve it? private void btn_Recieve_Click(object sender, EventArgs e) { TcpListener server = null; // Set the TcpListener on port 13000. Int32 port = 13000; IPAddress localAddr = IPAddress.Parse("192.168.1.201"); // TcpListener server = new TcpListener(port); server = new TcpListener(localAddr, port); // Start listening for client requests. server.Start(); // Buffer for reading data Byte[] bytes = new Byte[277577]; String data; data = null; // Perform a blocking call to accept requests. // You could also user server.AcceptSocket() here. TcpClient client = server.AcceptTcpClient(); NetworkStream stream = client.GetStream(); int i; i = stream.Read(bytes, 0, 277577); BinaryWriter writer = new BinaryWriter(File.Open("GoodLuckToMe.jpg", FileMode.Create)); writer.Write(bytes); writer.Close(); client.Close(); }

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  • Accessing type members outside the class in Scala

    - by Pekka Mattila
    Hi, I am trying to understand type members in Scala. I wrote a simple example that tries to explain my question. First, I created two classes for types: class BaseclassForTypes class OwnType extends BaseclassForTypes Then, I defined an abstract type member in trait and then defined the type member in a concerete class: trait ScalaTypesTest { type T <: BaseclassForTypes def returnType: T } class ScalaTypesTestImpl extends ScalaTypesTest { type T = OwnType override def returnType: T = { new T } } Then, I want to access the type member (yes, the type is not needed here, but this explains my question). Both examples work. Solution 1. Declaring the type, but the problem here is that it does not use the type member and the type information is duplicated (caller and callee). val typeTest = new ScalaTypesTestImpl val typeObject:OwnType = typeTest.returnType // declare the type second time here true must beTrue Solution 2. Initializing the class and using the type through the object. I don't like this, since the class needs to be initialized val typeTest = new ScalaTypesTestImpl val typeObject:typeTest.T = typeTest.returnType // through an instance true must beTrue So, is there a better way of doing this or are type members meant to be used only with the internal implementation of a class?

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  • Tracking the user function that threw the exception

    - by makerofthings7
    I've been given a large application with only one try..catch at the outer most level. This application also throws exceptions all the time, and is poorly documented. Is there any pattern I can implement that will tell me what user method is being called, the exception being thrown, and also the count of exceptions? I'm thinking of using a dictionary with reflection to get the needed information, but I'm not sure if this will work. What do you think?

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  • Confusion regarding laziness

    - by Abhinav Kaushik
    I have a function myLength = foldl (\ x _ -> x + 1) 0 which fails with stack overflow with input around 10^6 elements (myLength [1..1000000] fails). I believe that is due to the thunk build up since when I replace foldl with foldl', it works. So far so good. But now I have another function to reverse a list : myReverse = foldl (\ acc x -> x : acc) [] which uses the lazy version foldl (instead of foldl') When I do myLength . myReverse $ [1.1000000]. This time it works fine. I fail to understand why foldl works for the later case and not for former?

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  • Any ideas on How to search a 2D array quickly?

    - by Tattat
    I jave a 2D array like this, just like a matrix: {{1, 2, 4, 5, 3, 6}, {8, 3, 4, 4, 5, 2}, {8, 3, 4, 2, 6, 2}, //code skips... ... } I want to get all the "4" position, instead of searching the array one by way, and return the position, how can I search it faster / more efficient? thz in advance.

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  • Software Development Lifecycle

    - by j-t-s
    Hi All Our investor wants a SDLC. I've never written one before, and I don't have enough time to go and buy a book, or spend much time learning about them. But from what I'vebeen told about them, is basically that you need to list requirements (what needs to be done), and list what has already been done. Is this correct? thank you

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  • Problem with a blocking network task

    - by user326967
    Hello everyone. I'm new in Java so please forgive any obscene errors that I may make :) I'm developing a program in Java that among other things it should also handle clients that will connect to a server. The server has 3 threads running, and I have created them in the following way : DaemonForUI du; DaemonForPort da; DaemonForCheck dc; da = new DaemonForPort(3); dc = new DaemonForCheck(5); du = new DaemonForUI(7); Thread t_port = new Thread(da); Thread t_check = new Thread(dc); Thread t_ui = new Thread(du); t_port.setName("v1.9--PORTd"); t_check.setName("v1.9-CHECKd"); t_ui.setName("v1.9----UId"); t_port.start(); t_check.start(); t_ui.start(); Each thread handles a different aspect of the complete program. The thread t_ui is responsible to accept asynchronous incoming connections from clients, process the sent data and send other data back to the client. When I remove all the commands from the previous piece of code that has to with the t_ui thread, everything runs ok which in my case means that the other threads are printing their debug messages. If I set the t_ui thread to run too, then the whole program blocks at the "accept" of the t_ui thread. After reading at online manuals I saw that the accepted connections should be non-blocking, therefore use something like that : public ServerSocketChannel ssc = null; ssc = ServerSocketChannel.open(); ssc.socket().bind(new InetSocketAddress(port)); ssc.configureBlocking(false); SocketChannel sc = ssc.accept(); if (sc == null) { ; } else { System.out.println("The server and client are connected!"); System.out.println("Incoming connection from: " + sc.socket().getRemoteSocketAddress()); in = new DataInputStream(new BufferedInputStream(sc.socket().getInputStream())); out = new DataOutputStream(new BufferedOutputStream(sc.socket().getOutputStream())); //other magic things take place after that point... The thread for t_ui is created as follows : class DaemonForUI implements Runnable{ private int cnt; private int rr; public ListenerForUI serverListener; public DaemonForUI(int rr){ cnt = 0; this.rr = rr; serverListener = new ListenerForUI(); } public static String getCurrentTime() { final String DATE_FORMAT_NOW = "yyyy-MM-dd HH:mm:ss"; Calendar cal = Calendar.getInstance(); SimpleDateFormat sdf = new SimpleDateFormat(DATE_FORMAT_NOW); return (sdf.format(cal.getTime())); } public void run() { while(true) { System.out.println(Thread.currentThread().getName() + "\t (" + cnt + ")\t (every " + rr + " sec) @ " + getCurrentTime()); try{ Thread.sleep(rr * 1000); cnt++; } catch (InterruptedException e){ e.printStackTrace(); } } } } Obviously, I'm doing something wrong at the creation of the socket or at the use of the thread. Do you know what is causing the problem? Every help would be greatly appreciated.

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  • Relational Clausal Logic question: what is a Herbrand interpretation

    - by anotherstat
    I'm having a hard time coming to grips with relational clausal logic, and I'm not sure if this is the place to ask but it would be help me so much with revision if anyone could provide guidance with the following questions. Let P be the program: academic(X); student(X); other_staff(X):- works_in(X, university). :-student(john). :-other_staff(john). works_in(john, university) Question: Which are the Herbrand interpreations of P? AS

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  • Why does this Object wonk out & get deleted ?

    - by brainydexter
    Stepping through the debugger, the BBox object is okay at the entry of the function, but as soon as it enters the function, the vfptr object points to 0xccccc. I don't get it. What is causing this ? Why is there a virtual table reference in there when the object is not derived from other class. (Though, it resides in GameObject from which my Player class inherits and I retrieve the BBox from within player. But, why does the BBox have the reference ? Shouldn't it be player who should be maintained in that reference ?) For 1; some code for reference: A. I retrieve the bounding box from player. This returns a bounding box as expected. I then send its address to GetGridCells. const BoundingBox& l_Bbox = l_pPlayer-GetBoundingBox(); boost::unordered_set < Cell*, CellPHash & l_GridCells = GetGridCells ( &l_Bbox ); B. This is where a_pBoundingBox goes crazy and gets that garbage value. boost::unordered_set< Cell*, CellPHash CollisionMgr::GetGridCells(const BoundingBox *a_pBoundingBox) { I think the following code is also pertinent, so I'm sticking this in here anyways: const BoundingBox& Player::GetBoundingBox(void) { return BoundingBox( &GetBoundingSphere() ); } const BoundingSphere& Player::GetBoundingSphere(void) { BoundingSphere& l_BSphere = m_pGeomMesh-m_BoundingSphere; l_BSphere.m_Center = GetPosition(); return l_BSphere; } // BoundingBox Constructor BoundingBox(const BoundingSphere* a_pBoundingSphere); Can anyone please give me some idea as to why this is happening? Also, if you want me to post more code, please do let me know. Thanks!

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  • Odd performance with C# Asynchronous server socket

    - by The.Anti.9
    I'm working on a web server in C# and I have it running on Asynchronous socket calls. The weird thing is that for some reason, when you start loading pages, the 3rd request is where the browser won't connect. It just keeps saying "Connecting..." and doesn't ever stop. If I hit stop. and then refresh, it will load again, but if I try another time after that it does the thing where it doesn't load again. And it continues in that cycle. I'm not really sure what is making it do that. The code is kind of hacked together from a couple of examples and some old code I had. Any miscellaneous tips would be helpful as well. Heres my little Listener class that handles everything (pastied here. thought it might be easier to read this way) using System; using System.Collections.Generic; using System.Net; using System.Net.Sockets; using System.Text; using System.Threading; namespace irek.Server { public class Listener { private int port; private Socket server; private Byte[] data = new Byte[2048]; static ManualResetEvent allDone = new ManualResetEvent(false); public Listener(int _port) { port = _port; } public void Run() { server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); IPEndPoint iep = new IPEndPoint(IPAddress.Any, port); server.Bind(iep); Console.WriteLine("Server Initialized."); server.Listen(5); Console.WriteLine("Listening..."); while (true) { allDone.Reset(); server.BeginAccept(new AsyncCallback(AcceptCon), server); allDone.WaitOne(); } } private void AcceptCon(IAsyncResult iar) { allDone.Set(); Socket s = (Socket)iar.AsyncState; Socket s2 = s.EndAccept(iar); SocketStateObject state = new SocketStateObject(); state.workSocket = s2; s2.BeginReceive(state.buffer, 0, SocketStateObject.BUFFER_SIZE, 0, new AsyncCallback(Read), state); } private void Read(IAsyncResult iar) { try { SocketStateObject state = (SocketStateObject)iar.AsyncState; Socket s = state.workSocket; int read = s.EndReceive(iar); if (read > 0) { state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, read)); if (s.Available > 0) { s.BeginReceive(state.buffer, 0, SocketStateObject.BUFFER_SIZE, 0, new AsyncCallback(Read), state); return; } } if (state.sb.Length > 1) { string requestString = state.sb.ToString(); // HANDLE REQUEST HERE // Temporary response string resp = "<h1>It Works!</h1>"; string head = "HTTP/1.1 200 OK\r\nContent-Type: text/html;\r\nServer: irek\r\nContent-Length:"+resp.Length+"\r\n\r\n"; byte[] answer = Encoding.ASCII.GetBytes(head+resp); // end temp. state.workSocket.BeginSend(answer, 0, answer.Length, SocketFlags.None, new AsyncCallback(Send), state.workSocket); } } catch (Exception) { return; } } private void Send(IAsyncResult iar) { try { SocketStateObject state = (SocketStateObject)iar.AsyncState; int sent = state.workSocket.EndSend(iar); state.workSocket.Shutdown(SocketShutdown.Both); state.workSocket.Close(); } catch (Exception) { } return; } } } And my SocketStateObject: public class SocketStateObject { public Socket workSocket = null; public const int BUFFER_SIZE = 1024; public byte[] buffer = new byte[BUFFER_SIZE]; public StringBuilder sb = new StringBuilder(); }

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