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  • How can I pre-authorize authopen?

    - by Georg
    I'm using authopen inside one of my programs to modify files owned by root. As can be seen in the screenshot below authopen asks for a admin password. What I'd like to achieve is that the dialog shows my app's name and then passes the authorization to authopen. Code Launching authopen which returns an authorized file descriptor. int pipe[2]; socketpair(AF_UNIX, SOCK_STREAM, 0, pipe); if (fork() == 0) { // child // close parent's pipe close(pipe[0]); dup2(pipe[1], STDOUT_FILENO); const char *authopenPath = "/usr/libexec/authopen"; execl(authopenPath, authopenPath, "-stdoutpipe", [self.device.devicePath fileSystemRepresentation], NULL); NSLog(@"Fatal error, quitting."); exit(-1); } // parent // close childs's pipe close(pipe[1]); // get file descriptor through sockets I'd really like not to use AuthorizationExecuteWithPrivileges because then I'd have to get more rights than I want to.

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  • Dynamics of the using keyword

    - by AngryHacker
    Consider the following code: // module level declaration Socket _client; void ProcessSocket() { _client = GetSocketFromSomewhere(); using (_client) { DoStuff(); // receive and send data Close(); } } void Close() { _client.Close(); _client = null; } Given that that the code calls the Close() method, which closes the _client socket and sets it to null, while still inside the `using' block, what exactly happens behind the scenes? Does the socket really get closed? Are there side effects? P.S. This is using C# 3.0 on the .NET MicroFramework, but I suppose the c#, the language, should function identically. The reason i am asking is that occasionally, very rarely, I run out of sockets (which is a very precious resource on a .NET MF devices).

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  • TcpListener.Start() does not open the port

    - by SoMoS
    Hello, I have a class that inherits from the TcpListener, this class Shadows the Start method just to call the base Start() and the base BeginAcceptTcpClient(). From time to time the method is called but the port is not opened (netstat does not show the port open). The class looks like this Public Class ExtendedTcpListener Inherits System.Net.Sockets.TcpListener Public Shadows Sub Start() SyncLock (m_stopLock) MyBase.Start() MyBase.BeginAcceptTcpClient(AddressOf Me.CompleteAcceptTcpClient, Me) My.Application.Log.WriteEntry("Extended Tcp Listener started ...", TraceEventType.Verbose) End SyncLock End Sub Any idea on what's happening or how to debug the issue? As the Start() is called without exception I expected to find the port always opened (the log is always written). Extra information: when the Start method works fine it works each time until app is restarted. When the Start method does not work it won't work again until the app is restarted.

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  • How could I embed a html/css/js view in a webstart application

    - by phmr
    I would like to use a html/css/js view in my webstart project without requesting all permissions. I figured out that I could use the java HTTPServer to process the requests but I need a way to avoid using real sockets, so that the HTTPServer instantiation doesn't ask for some permission. Do you know any projects that achieve that ? and if not, what should I do to get an HTTPServer completely working locally (without hitting boundaries...) ? edit: maybe an HTTPServer is too much, I maybe only need a HttpHandler..

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  • Reading UDP Packets

    - by Thomas Mathiesen
    I am having some trouble dissecting a UDP packet. I am receiving the packets and storing the data and sender-address in variables 'data' and 'addr' with: data,addr = UDPSock.recvfrom(buf) This parses the data as a string, that I am now unable to turn into bytes. I know the structure of the datagram packet which is a total of 28 bytes, and that the data I am trying to get out is in bytes 17:28. I have tried doing this: mybytes = data[16:19] print struct.unpack('>I', mybytes) --> struct.error: unpack str size does not match format And this: response = (0, 0, data[16], data[17], 6) bytes = array('B', response[:-1]) print struct.unpack('>I', bytes) --> TypeError: Type not compatible with array type And this: print "\nData byte 17:", str.encode(data[17]) --> UnicodeEncodeError: 'ascii' codec can't encode character u'\xff' in position 0: ordinal not in range(128) And I am not sure what to try next. I am completely new to sockets and byte-conversions in Python, so any advice would be helpful :) Thanks, Thomas

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  • How to implement a bidirectional "mailbox service" over tcp?

    - by igorgatis
    The idea is to allow to peer processes to exchange messages (packets) over tcp as much asynchronously as possible. The way I'd like it to work is each process to have an outbox and an inbox. The send operation is just a push on the outbox. The receive operation is just a pop on the inbox. Underlying protocol would take care of the communication details. Is there a way to implement such mechanism using a single TCP connection? How would that be implemented using BSD sockets and modern OO Socket APIs (like Java or C# socket API)?

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  • Java ServerSocket Multiple Listen Instances

    - by ikurtz
    i have a java game app that uses sockets to communicate with each other. the issue is when i do a socket listen (server), i can run another instance of the game on the same machine using the same port as before to listen, and it results in listening again. now i have two instances of the application both listening on the same port. you can imagine only one connects when a connection comes through. the question is: how do i prevent the app from listening on the same port as another instance is already listening to? thanks in advance. EDIT: serverSocket = new ServerSocket(serverPort, backlog); im using this. should i try to use: ServerSocket(int port, int backlog, InetAddress bindAddr) instead? EDIT: SOLVED! i did not handle the exception only trapped it. now it is working well. thanks for your inputs.

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  • fastest (low latency) method for Inter Process Communication between Java and C/C++

    - by Bastien
    Hello, I have a Java app, connecting through TCP socket to a "server" developed in C/C++. both app & server are running on the same machine, a Solaris box (but we're considering migrating to Linux eventually). type of data exchanged is simple messages (login, login ACK, then client asks for something, server replies). each message is around 300 bytes long. Currently we're using Sockets, and all is OK, however I'm looking for a faster way to exchange data (lower latency), using IPC methods. I've been researching the net and came up with references to the following technologies: - shared memory - pipes - queues but I couldn't find proper analysis of their respective performances, neither how to implement them in both JAVA and C/C++ (so that they can talk to each other), except maybe pipes that I could imagine how to do. can anyone comment about performances & feasibility of each method in this context ? any pointer / link to useful implementation information ? thanks for your help

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  • How can I run NHibenate queries asynchronously?

    - by andrey-tsykunov
    Hello, One way to increase scalability of the server application is to run IO-bound operation (reading files, sockets, web requests, database requests etc) asynchronously. This does not mean run then in the ThreadPool which will just block threads while operation is being executed. The correct way is to use asynchronous API (BeginRead, BeginGetResponse, BeginExecuteReader etc). The problem is well described in CLR vi C# book. Here is some article about asynchronous queries in Linq to SQL. Are any ways to execute Nhibernate query asynchonously? What about Linq to NHibernate? Thank you, Andrey

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  • Copy Structure To Another Program

    - by Steven
    Long story, long: I am adding a web interface (ASPX.NET: VB) to a data acquisition system developed with LabVIEW which outputs raw data files. These raw data files are the binary representation of a LabVIEW cluster (essentially a structure). LabVIEW provides functions to instantiate a class or structure or call a method defined in a .NET DLL file. I plan to create a DLL file containing a structure definition and a class with methods to transfer the structure. When the webpage requests data, it would call a LabVIEW executable with a filename parameter. The LabVIEW code would instantiate the structure, populate the structure from the data file, then call the method to transfer the data back to the website. Long story, short: How do you recommend I transfer (copy) an instance of a structure from one .NET program to a VB.NET program? Ideas considered: sockets, temp file, xml file, config file, web services, CSV, some type of serialization, shared memory

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  • How to reduce compilation times with Boost Asio

    - by Artyom
    Boost.Asio is great library but it has one huge drawback -- extreamly slow compilation times. A simple implementation (really simple) of HTTP protocol (about 1k lines of code) requires about 13.5s to compile under GCC 4.4! I tryed to use PCH but it does not improve compilation times too much (about 1s. only). So are there any tutorials on how to make Boost.Asio compilation times faster? For example what headers should I exactly include for what class. I use for example: io_service, tcp::ip::sockets, tcp::ip::acceptor, deadline_timer, buffers and few functions like async_read, async_write. Any suggestions? P.S.: I do use pimpl whenever I can.

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  • [java] Efficiency of while(true) ServerSocket Listen

    - by Submerged
    I am wondering if a typical while(true) ServerSocket listen loop takes an entire core to wait and accept a client connection (Even when implementing runnable and using Thread .start()) I am implementing a type of distributed computing cluster and each computer needs every core it has for computation. A Master node needs to communicate with these computers (invoking static methods that modify the algorithm's functioning). The reason I need to use sockets is due to the cross platform / cross language capabilities. In some cases, PHP will be invoking these java static methods. I used a java profiler (YourKit) and I can see my running ServerSocket listen thread and it never sleeps and it's always running. Is there a better approach to do what I want? Or, will the performance hit be negligible? Please, feel free to offer any suggestion if you can think of a better way (I've tried RMI, but it isn't supported cross-language. Thanks everyone

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  • Adobe AIR+AJAX ftp library

    - by Gaurav
    Hi, I have just started creating an Adobe AIR+AJAX app which will need to upload and download files from the server using ftp functionality. Right now what is happening is I need to use sockets for this which is way to confusing and difficult to maintain. So, I was wondering if anybody has developed a javascript library or functionality for ftp? I don't want to rely on any serverside script for this. There is an ftp library for flex but it is quite confusing with not much documentation. Can anybody help? Thanks, Gaurav

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  • Form gets disposed somehow

    - by mnn
    I have a client-server application, in which I use classic Sockets and threads for receiving/sending data and listening for clients. The application works fine, but after some random time I get the ObjectDisposedException: System.ObjectDisposedException: Cannot access a disposed object. Object name: 'MainForm'. at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous) at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args) at System.Windows.Forms.Control.Invoke(Delegate method) That code is called from client Socket thread and I use Invoke() method to run the code on UI thread. I'm sure that I don't manually dispose the form nor using Close() (form is closed by user clicking Close button), so I don't know what could cause its disposing.

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  • Fast single thread comet server, possible?

    - by Pepijn
    I recently encountered a few cases where a server would distribute an event stream that contains the exact same data for all listeners, such as a 'recent activity' box. It occurred to me that it is quite strange and inefficient to have a server like Apache run a thread processing and querying the database for every single comet stream containing the same data. What I would do for those global(not per user) streams is run a single thread that continuously emits data, and a new (green)thread for every new request that outputs the headers and then 'merges' into the main thread. Is it possible for one thread to serve multiple sockets, or for multiple clients to listen to the same socket? An example o = event # threads received | a b # 3 o / / # 3 - |/_/ | # 1 o c # 2 a, b | / o/ # 2 a, b o # 1 a, b, c | # connection b closed o # 1 a, c Does something like this exist? Would it work? Is it possible to do? Disclaimer: I'm not a server expert.

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  • Why Bluetooth needs DBUS way of communication in android?

    - by Rajesh SO
    I am newbie to Android DBUS, recently I was informed that I need to use DBUS to implement Bluetooth in Android, from DBUS documentation I see DBUS is used for communication medium between two applications. In Android apps -apps communication is through intents, if so why do we need DBUS for Bluetooth ? Is that DBUS serves as communication medium for networking (IP) between two apps since it is built over sockets? Please correct me if my understanding is wrong, any more information on DBUS along with Bluetooth implementation in Android is appreciated. Thanks.

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  • What is the best way to transmit Java objects over a network

    - by tomdee
    I am trying to transmit objects of a particular class from one server to another. The options I'm looking at are: Serialize the data as JSON and send it over the wire using HTTP, and de-serialize at the other end. Serialize the data into some binary form and transmit using TCP sockets. What are the best practices in this area? What are the gotchas? Ideally I would like the interface to be versioned, so the sender and receiver can be upgraded independently. I'm considering the JSON approach as I already have code that will serialize/deserialize the objects into JSON.

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  • Code golf: Word frequency chart

    - by ChristopheD
    The challenge: Build an ASCII chart of the most commonly used words in a given text. The rules: Only accept a-z and A-Z (alphabetic characters) as part of a word. Ignore casing (She == she for our purpose). Ignore the following words (quite arbitary, I know): the, and, of, to, a, i, it, in, or, is Clarification: considering don't: this would be taken as 2 different 'words' in the ranges a-z and A-Z: (don and t). Optionally (it's too late to be formally changing the specifications now) you may choose to drop all single-letter 'words' (this could potentially make for a shortening of the ignore list too). Parse a given text (read a file specified via command line arguments or piped in; presume us-ascii) and build us a word frequency chart with the following characteristics: Display the chart (also see the example below) for the 22 most common words (ordered by descending frequency). The bar width represents the number of occurences (frequency) of the word (proportionally). Append one space and print the word. Make sure these bars (plus space-word-space) always fit: bar + [space] + word + [space] should be always <= 80 characters (make sure you account for possible differing bar and word lenghts: e.g.: the second most common word could be a lot longer then the first while not differing so much in frequency). Maximize bar width within these constraints and scale the bars appropriately (according to the frequencies they represent). An example: The text for the example can be found here (Alice's Adventures in Wonderland, by Lewis Carroll). This specific text would yield the following chart: _________________________________________________________________________ |_________________________________________________________________________| she |_______________________________________________________________| you |____________________________________________________________| said |____________________________________________________| alice |______________________________________________| was |__________________________________________| that |___________________________________| as |_______________________________| her |____________________________| with |____________________________| at |___________________________| s |___________________________| t |_________________________| on |_________________________| all |______________________| this |______________________| for |______________________| had |_____________________| but |____________________| be |____________________| not |___________________| they |__________________| so For your information: these are the frequencies the above chart is built upon: [('she', 553), ('you', 481), ('said', 462), ('alice', 403), ('was', 358), ('that ', 330), ('as', 274), ('her', 248), ('with', 227), ('at', 227), ('s', 219), ('t' , 218), ('on', 204), ('all', 200), ('this', 181), ('for', 179), ('had', 178), (' but', 175), ('be', 167), ('not', 166), ('they', 155), ('so', 152)] A second example (to check if you implemented the complete spec): Replace every occurence of you in the linked Alice in Wonderland file with superlongstringstring: ________________________________________________________________ |________________________________________________________________| she |_______________________________________________________| superlongstringstring |_____________________________________________________| said |______________________________________________| alice |________________________________________| was |_____________________________________| that |______________________________| as |___________________________| her |_________________________| with |_________________________| at |________________________| s |________________________| t |______________________| on |_____________________| all |___________________| this |___________________| for |___________________| had |__________________| but |_________________| be |_________________| not |________________| they |________________| so The winner: Shortest solution (by character count, per language). Have fun! Edit: Table summarizing the results so far (2012-02-15) (originally added by user Nas Banov): Language Relaxed Strict ========= ======= ====== GolfScript 130 143 Perl 185 Windows PowerShell 148 199 Mathematica 199 Ruby 185 205 Unix Toolchain 194 228 Python 183 243 Clojure 282 Scala 311 Haskell 333 Awk 336 R 298 Javascript 304 354 Groovy 321 Matlab 404 C# 422 Smalltalk 386 PHP 450 F# 452 TSQL 483 507 The numbers represent the length of the shortest solution in a specific language. "Strict" refers to a solution that implements the spec completely (draws |____| bars, closes the first bar on top with a ____ line, accounts for the possibility of long words with high frequency etc). "Relaxed" means some liberties were taken to shorten to solution. Only solutions shorter then 500 characters are included. The list of languages is sorted by the length of the 'strict' solution. 'Unix Toolchain' is used to signify various solutions that use traditional *nix shell plus a mix of tools (like grep, tr, sort, uniq, head, perl, awk).

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  • Why are there so many man-made edge cases in IT, and is there any hope for simplification / unificat

    - by Hamish Grubijan
    This question is meant to generate discussion and so it is marked as community wiki. My observation is that the field of information technology grows so rapidly and randomly, that for many it takes a lot of time to learn many intricacies of some tools that will be obsolete in just short 3 years. If you look at the questions asked on StackOverflow ... at least half of them stem from the fact that some language / tool / API / protocol was poorly designed, is backwards and has gotchas. There are so many things which distract developers from converting English into machine code; instead they spend their time configuring stuff and gluing together things that do not really fit. How many times do you pick up somebody else's project (or someone picks up yours :) ) and realize that this program does not need half of the dialogs that it has, and that the logic can be simplified a great deal? But, it had to be made and sold here before a better thing is made and sold elsewhere, and hence all this rush. I often wish that things would just slow down. I do not want Microsoft Windows to run on my car's computer, my watch, my table, my toaster oven, and my toilet seat. I'd rather have Windows that DOES NOT HAVE WINDOWS REGISTRY, I'd rather have Windows that allows two different programs to work on the same file at the same time, the way it works on Unix systems. Microsoft is just an example. I am looking forward to the day when I do not have to worry about Windows vs Unix new line break, when System32 actually means that this directory contains 32-bit binaries, and not 64-bit ones, the day when dll hell and manifest hell are no longer an issue, the day when it takes me a lot less than 3 months on a new job to learn the system. I do not mean learning the entire code base of a product (depending on the size of it, it can take a long time). I mean - remembering which build-assisting scripts are written in Perl and which version of it, and which ones are done through .bat files, when do I need to manually make every file in some directory writable before running a script, or else a critical step of a database maintenance home-grown tool will bomb, and it will take 2 days to clean that up. Makes me wonder if humans enslaved computers, or if it is the other way around. The key is that improving those things will not bring extra revenue, and hence those taking the time to fix crap like that are not "business focused". However, these imperfections irritate me immensely, particularly because my memory is limited - I can hold only a small portion of that useless knowledge of a system in my head at any given point in time. I must not be alone. Did you also happen to notice that a programmer can waste a lot of time on things that should have been a lot more straight-forward? Is there hope? Will things get better/simpler in the future, or will there be a lot more IT crap floating around? I suppose I see diversity of tools, protocols, etc. as a bad thing. Thank you for participation.

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  • Socket : can an asynchronous Receive returns without reading all the bytes I asked for?

    - by NorthWind
    Hi; I was reading an article on Vadym Stetsiak's blog about how to transfer variable length messages with async sockets (url: http://vadmyst.blogspot.com/2008/03/part-2-how-to-transfer-fixed-sized-data.html). He says : What to expect when multiple messages arrive at the server? While dealing with multiple messages one has to remember that receive operation can return arbitrary number of bytes being read from the net. Typically that size is from 0 to specified buffer length in the Receive or BeginReceive methods. So, even if I tell BeginReceive to read 100 bytes, it may read less than that and returns??? I am developing a network-enabled software (TCP/IP), and I always receive the same exact number of bytes I asked for. I don't even understand the logic : why would Receive completes asynchronously if it didn't get every byte I asked for ... just keep waiting. Maybe it has something to do with IP vs TCP? Thank you for your help.

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  • innovation for technical high school

    - by gnuze
    I work in a high school in Italy. Our goal is forming computer programmers in 5 years. Nowaday, we teach vb.net on Win ( desktop applications using ADO on Access ), C on linux ( process, threads ) , C++ on Linux ( sockets TCP/UDP with UML ), and a bit of ASP.net, flash programming, PHP, Joomla and PIC Microcontrollers. We are looking for something innovative to add in our programs of study, but every teacher have a different point of view: we are debating about python, C#, Arduino, Silverlight and smartphones programming. Any suggestions? Tx in advance.

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  • Bind Data after TCP receive.

    - by gtas
    I have this strange problem all day now. I dunno if you handled something similar. I used two different serializers and now i know its not this problem. Im sending some data over TCP Sockets. Serialize - Send - Deserialize, everything works ok, i can get my objects search through them, use they're properties! But, if e.g receive a BusinessObject[] and convert into List<BusinessObject>, then bind the list in a Control.DataSource = businessObjectList; BOOM! NotSupportedException. Tried it with 3 different controls. Same behaviour. My head is empty of ideas right now!! The Send TCP happens on Desktop Framework, Receive on Compact Framework. But i dont think this has to do with anything. I wish for an explanation on this!

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  • Efficiency of while(true) ServerSocket Listen

    - by Submerged
    I am wondering if a typical while(true) ServerSocket listen loop takes an entire core to wait and accept a client connection (Even when implementing runnable and using Thread .start()) I am implementing a type of distributed computing cluster and each computer needs every core it has for computation. A Master node needs to communicate with these computers (invoking static methods that modify the algorithm's functioning). The reason I need to use sockets is due to the cross platform / cross language capabilities. In some cases, PHP will be invoking these java static methods. I used a java profiler (YourKit) and I can see my running ServerSocket listen thread and it never sleeps and it's always running. Is there a better approach to do what I want? Or, will the performance hit be negligible? Please, feel free to offer any suggestion if you can think of a better way (I've tried RMI, but it isn't supported cross-language. Thanks everyone

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  • my realtime network receiving time differs a lot, anyone can help?

    - by sguox002
    I wrote a program using tcpip sockets to send commands to a device and receive the data from the device. The data size would be around 200kB to 600KB. The computer is directly connected to the device using a 100MB network. I found that the sending packets always arrive at the computer at 100MB/s speed (I have debugging information on the unit and I also verified this using some network monitoring software), but the receiving time differs a lot from 40ms to 250ms, even if the size is the same (I have a receiving buffer about 700K and the receiving window of 8092 bytes and changing the window size does not change anything). The phenomena differs also on different computers, but on the same computer the problem is very stable. For example, receiving 300k bytes on computer a would be 40ms, but it may cost 200ms on another computer. I have disabled firewall, antivirus, all other network protocol except the TCP/IP. Any experts on this can give me some hints?

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  • Writing to a java socket channel which should be closed does not generate an exception

    - by Dan Serfaty
    Hi all, We have a java server that keeps a socket channel open with an Android client in order to provide push capabilities to our client application. However, after putting the Android in airplane mode, which I expected would sever the connection, the server can still write to the SocketChannel object associated with that Android client and no error is thrown. Calling SocketChannel.isConnected() before writing to it returns true. What are we missing? Is the handling of sockets different with mobile devices? Thanks in advance for your help.

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