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  • How to migrate existing udp application to raw sockets

    - by osgx
    Hello Is there a tutorial for migration from plain udp sockets (linux, C99/C++, recv syscall is used) to the raw sockets? According to http://aschauf.landshut.org/fh/linux/udp_vs_raw/ch03s04.html raw socket is much faster than udp. Application is client-server. client is proprietary and must use exactly same procotol as it was with udp server. But server can be a bit faster with raw sockets. What parts of udp I must to implement in server? Is there a "quick migration" libraries?

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  • Are Scala "continuations" just a funky syntax for defining and using Callback Functions?

    - by Alex R
    And I mean that in the same sense that a C/Java for is just a funky syntax for a while loop. I still remember when first learning about the for loop in C, the mental effort that had to go into understanding the execution sequence of the three control expressions relative to the loop statement. Seems to me the same sort of effort has to be applied to understand Continuations (in Scala and I guess probably other languages). And then there's the obvious follow-up question... if so, then what's the point? It seems like a lot of pain (language complexity, programmer errors, unreadable programs, etc) for no gain.

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  • Truly declarative language?

    - by gjvdkamp
    Hi all, Does anyone know of a truly declarative language? The behaviour I'm looking for is kind of what Excel does, where I can define variables and formulas, and have the formula's result change when the input changes (without having set the answer again myself) The behaviour I'm looking for is best shown with this pseudo code: X = 10 // define and assign two variables Y = 20; Z = X + Y // declare a formula that uses these two variables X = 50 // change one of the input variables ?Z // asking for Z should now give 70 (50 + 20) I've tried this in a lot of languages like F#, python, matlab etc, but every time i try this they come up with 30 instead of 70. Wich is correct from an imperative point of view, but i'm looking for a more declerative behaviour if you know what i mean. And this is just a very simple calculation. When things get more difficult it should handle stuff like recursion and memoization automagically. The code below would obviously work in C# but it's just so much code for the job, i'm looking for something a bit more to the point without all that 'technical noise' class BlaBla{ public int X {get;set;} // this used to be even worse before 3.0 public int Y {get;set;} public int Z {get{return X + Y;}} } static void main(){ BlaBla bla = new BlaBla(); bla.X = 10; bla.Y = 20; // can't define anything here bla.X = 50; // bit pointless here but I'll do it anyway. Console.Writeline(bla.Z);// 70, hurray! } This just seems like so much code, curly braces and semicolons that add nothing. Is there a language/ application (apart from Exel) that does this? Maybe I'm no doing it right in the mentioned langauges, or I've completely missed an app that does just this. I prototyped a language/ application that does this (along with some other stuff) and am thinking of productizing it. I just can't believe it's not there yet. Don't want to waste my time. Thanks in advance, Gert-Jan

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  • How do i write tasks? (parallel code)

    - by acidzombie24
    I am impressed with intel thread building blocks. I like how i should write task and not thread code and i like how it works under the hood with my limited understanding (task are in a pool, there wont be 100 threads on 4cores, a task is not guaranteed to run because it isnt on its own thread and may be far into the pool. But it may be run with another related task so you cant do bad things like typical thread unsafe code). I wanted to know more about writing task. I like the 'Task-based Multithreading - How to Program for 100 cores' video here http://www.gdcvault.com/sponsor.php?sponsor_id=1 (currently second last link. WARNING it isnt 'great'). My fav part was 'solving the maze is better done in parallel' which is around the 48min mark (you can click the link on the left side. That part is really all you need to watch if any). However i like to see more code examples and some API of how to write task. Does anyone have a good resource? I have no idea how a class or pieces of code may look after pushing it onto a pool or how weird code may look when you need to make a copy of everything and how much of everything is pushed onto a pool.

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  • How to maintain a persistant network-connection between two applications over a network?

    - by John
    I was recently approached by my management with an interesting problem - where I am pretty sure I am telling my bosses the correct information but I really want to make sure I am telling them the correct stuff. I am being asked to develop some software that has this function: An application at one location is constantly processing real-time data every second and only generates data if the underlying data has changed in any way. On the event that the data has changed send the results to another box over a network Maintains a persistent connection between the both machines, altering the remote box if for some reason the network connection went down From what I understand, I imagine that I need to do some reading on doing some sort of TCP/IP socket-level stuff. That way if the connection is dropped the remote location will be aware that the data it has received may be stale. However management seems to be very convinced that this can be accomplished using SOAP. I was under the impression that SOAP is more or less a way for a client to initiate a procedure from a server and get some results via the HTTP protocol. Am I wrong in assuming this? I haven't been able to find much information on how SOAP might be able to solve a problem like this. I feel like a lot of people around my office are using SOAP as a buzzword and that has generated a bit of confusion over what SOAP actually is - and is capable of. Any thoughts on how to accomplish this task would be appreciated!

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  • How do i write task? (parallel code)

    - by acidzombie24
    I am impressed with intel thread building blocks. I like how i should write task and not thread code and i like how it works under the hood with my limited understanding (task are in a pool, there wont be 100 threads on 4cores, a task is not guaranteed to run because it isnt on its own thread and may be far into the pool. But it may be run with another related task so you cant do bad things like typical thread unsafe code). I wanted to know more about writing task. I like the 'Task-based Multithreading - How to Program for 100 cores' video here http://www.gdcvault.com/sponsor.php?sponsor_id=1 (currently second last link. WARNING it isnt 'great'). My fav part was 'solving the maze is better done in parallel' which is around the 48min mark (you can click the link on the left side). However i like to see more code examples and some API of how to write task. Does anyone have a good resource? I have no idea how a class or pieces of code may look after pushing it onto a pool or how weird code may look when you need to make a copy of everything and how much of everything is pushed onto a pool.

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  • Using MonadPlus in FRP.Reactive.FieldTrip

    - by ony
    I'm studying FRP at this moment through FieldTrip adaptor. And hit the problem with strange way of frames scheduling and integration. So now I'm trying to build own marker Event for aligning Behaviour stepping. So... flipflop :: Behavior String flipflop = stepper "none" (xflip 2) where xflip t0 = do t <- withTimeE_ (atTime t0) return "flip" `mplus` xflop (t+3) xflop t0 = do t <- withTimeE_ (atTime t0) return "flop" `mplus` xflip (t+2) txtGeom = ((uscale2 (0.5::Float) *%) . utext . show <$>) main = anim2 (txtGeom . pure flipflop) Questions is: Why this example leads to memory leak? Is there safe way to build sequence of events where each next one is scheduled depending on previous?

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  • Translate imperative control flow with break-s/continue-s to haskell

    - by dorserg
    Consider the following imperative code which finds the largest palindrome among products of 3-digit numbers (yes, it's the one of the first tasks from "Project of [outstanding mathematician of 18th century]" site): curmax = 0 for i in range(999,100): for j in range(999,100): if ((i*j) < curmax): break if (pal(i*j)): curmax = i*j break print curmax As I'm learning Haskell currently, my question is, how do you translate this (and basically any imperative construct that contains something more complex than just plain iteration, e.g. breaks, continues, temporary variables and all this) to Haskell? My version is maxpal i curmax | i < 100 = curmax | otherwise = maxpal (i-1) (innerloop 999) where innerloop j | (j < 100) || (p < curmax) = curmax | pal p = p | otherwise = innerloop (j-1) where p = i*j main = print $ maxpal 999 0 but this looks like we're still in imperative uglytown. So what could you advise, what are the approaches of dealing with such cases FP-style?

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  • First Come, First Served process scheduling

    - by user253530
    i have 4 processes: p1 - bursts 5, priority: 3 p2 - bursts 8, priority: 2 p3 - bursts 12, priority: 2 p4 - bursts 6, priority: 1 Assuming that all processes arrive at the scheduler at the same time what is the average response time and average turnaround time? For FCFS is it ok to have them in the order p1, p2, p3, p4 in the execution queue?

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  • Rewriting Live TCP/IP (Layer 4) (i.e. Socket Layer) Streams

    - by user213060
    I have a simple problem which I'm sure someone here has done before... I want to rewrite Layer 4 TCP/IP streams (Not lower layer individual packets or frames.) Ettercap's etterfilter command lets you perform simple live replacements of Layer 4 TCP/IP streams based on fixed strings or regexes. Example ettercap scripting code: if (ip.proto == TCP && tcp.dst == 80) { if (search(DATA.data, "gzip")) { replace("gzip", " "); msg("whited out gzip\n"); } } if (ip.proto == TCP && tcp.dst == 80) { if (search(DATA.data, "deflate")) { replace("deflate", " "); msg("whited out deflate\n"); } } http://ettercap.sourceforge.net/forum/viewtopic.php?t=2833 I would like to rewrite streams based on my own filter program instead of just simple string replacements. Anyone have an idea of how to do this? Is there anything other than Ettercap that can do live replacement like this, maybe as a plugin to a VPN software or something? I would like to have a configuration similar to ettercap's silent bridged sniffing configuration between two Ethernet interfaces. This way I can silently filter traffic coming from either direction with no NATing problems. Note that my filter is an application that acts as a pipe filter, similar to the design of unix command-line filters: >[eth0] <----------> [my filter] <----------> [eth1]< What I am already aware of, but are not suitable: Tun/Tap - Works at the lower packet layer, I need to work with the higher layer streams. Ettercap - I can't find any way to do replacements other than the restricted capabilities in the example above. Hooking into some VPN software? - I just can't figure out which or exactly how. libnetfilter_queue - Works with lower layer packets, not TCP/IP streams. Again, the rewriting should occur at the transport layer (Layer 4) as it does in this example, instead of a lower layer packet-based approach. Exact code will help immensely! Thanks!

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  • Why did you decide "against" using Erlang?

    - by Zubair
    Have you actually "tried" (means programmed in, not just read an article on it) Erlang and decided against it for a project? If so, why? Also, if you have opted to go back to your old language, or to use another functional language like F#, Haskell, Clojure, Scala, or something else then this counts too, and state why.

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  • Does a good programmer need to have good spatial sense?

    - by lisa1234
    Do you need to have good spatial sense to be a good programmer? I have next to nothing of it (I think it has to do with the differing vision of my eyes). I've already coded quite little things but wonder if this interferes with the ability to 'imagine' the assembly of the code in case of a more complex program? Sorry for my english, I'm Austrian and not so used to write in English.. Thanks for your ansers..

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  • Listening Port Permanently. if file is on my stream, Get file. How to?

    - by Phsika
    i writed 2 client and server program. client dend file also server listen port and than get file.But i need My server App must listen on 51124 port permanently. if any file on my stream, show my message "there is a file on your stream" and than show me savefile dialog. But my server app in "Infinite loop". 1) listen 51124 port every time 2) do i have a file on my stream, show me a messagebox. private void Form1_Load(object sender, EventArgs e) { TcpListener Dinle = new TcpListener(51124); try { Dinle.Start(); Socket Baglanti = Dinle.AcceptSocket(); if (!Baglanti.Connected) { MessageBox.Show("No Connection!"); } else { while (true) { byte[] Dizi = new byte[250000]; Baglanti.Receive(Dizi, Dizi.Length, 0); string Yol; saveFileDialog1.Title = "Save File"; saveFileDialog1.ShowDialog(); Yol = saveFileDialog1.FileName; FileStream Dosya = new FileStream(Yol, FileMode.Create); Dosya.Write(Dizi, 0, Dizi.Length - 20); Dosya.Close(); listBox1.Items.Add("dosya indirildi"); listBox1.Items.Add("Dosya Boyutu=" + Dizi.Length.ToString()); listBox1.Items.Add("Indirilme Tarihi=" + DateTime.Now); listBox1.Items.Add("--------------------------------"); } } } catch (Exception) { throw; } } My Algorithm: if(AnyFileonStream()==true) { GetFile() //Also continue to listening 51124 port... } How can i do that?

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  • Rewriting Live TCP/IP (Layer 4) Streams

    - by user213060
    I want to rewrite TCP/IP streams. Ettercap's etterfilter command lets you perform simple live replacements of TCP/IP data based on fixed strings or regexes. Example: if (ip.proto == TCP && tcp.dst == 80) { if (search(DATA.data, "gzip")) { replace("gzip", " "); msg("whited out gzip\n"); } } if (ip.proto == TCP && tcp.dst == 80) { if (search(DATA.data, "deflate")) { replace("deflate", " "); msg("whited out deflate\n"); } } http://ettercap.sourceforge.net/forum/viewtopic.php?t=2833 I would like to rewrite streams based on my own filter program instead of just simple string replacements. Anyone have an idea of how to do this? Is there anything other than Ettercap that can do live replacement like this, maybe as a plugin to a VPN software or something? The rewriting should occur at the transport layer (Layer 4) as it does in this example, instead of a lower layer packet-based approach. Thanks!

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  • Is C really a subset of C++?

    - by Allopen
    What I mean is, can any C code be implemented via C++? Maybe just simply change a compiler? I know C is much more efficient and concise. But despite of these, can C++ used to implement all functions that are implemented by C?

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  • Why Software Sucks...and What You Can Do About It – book review

    - by DigiMortal
        How do our users see the products we are writing for them and how happy they are with our work? Are they able to get their work done without fighting with cool features and crashes or are they just switching off resistance part of their brain to survive our software? Yeah, the overall picture of software usability landscape is not very nice. Okay, it is not even nice. But, fortunately, Why Software Sucks...and What You Can Do About It by David S. Platt explains everything. Why Software Sucks… is book for software users but I consider it as a-must reading also for developers and specially for their managers whose politics often kills all usability topics as soon as they may appear. For managers usability is soft topic that can be manipulated the way it is best in current state of project. Although developers are not UI designers and usability experts they are still very often forced to deal with these topics and this is how usability problems start (of course, also designers are able to produce designs that are stupid and too hard to use for users, but this blog here is about development). I found this book to be very interesting and funny reading. It is not humor book but it explains you all so you remember later very well what you just read. It took me about three evenings to go through this book and I am still enjoying what I found and how author explains our weird young working field to end users. I suggest this book to all developers – while you are demanding your management to hire or outsource usability expert you are at least causing less pain to end users. So, go and buy this book, just like I did. And… they thanks to mr. Platt :) There is one book more I suggest you to read if you are interested in usability - Don't Make Me Think: A Common Sense Approach to Web Usability, 2nd Edition by Steve Krug. Editorial review from Amazon Today’s software sucks. There’s no other good way to say it. It’s unsafe, allowing criminal programs to creep through the Internet wires into our very bedrooms. It’s unreliable, crashing when we need it most, wiping out hours or days of work with no way to get it back. And it’s hard to use, requiring large amounts of head-banging to figure out the simplest operations. It’s no secret that software sucks. You know that from personal experience, whether you use computers for work or personal tasks. In this book, programming insider David Platt explains why that’s the case and, more importantly, why it doesn’t have to be that way. And he explains it in plain, jargon-free English that’s a joy to read, using real-world examples with which you’re already familiar. In the end, he suggests what you, as a typical user, without a technical background, can do about this sad state of our software—how you, as an informed consumer, don’t have to take the abuse that bad software dishes out. As you might expect from the book’s title, Dave’s expose is laced with humor—sometimes outrageous, but always dead on. You’ll laugh out loud as you recall incidents with your own software that made you cry. You’ll slap your thigh with the same hand that so often pounded your computer desk and wished it was a bad programmer’s face. But Dave hasn’t written this book just for laughs. He’s written it to give long-overdue voice to your own discovery—that software does, indeed, suck, but it shouldn’t. Table of contents Acknowledgments xiii Introduction Chapter 1: Who’re You Calling a Dummy? Where We Came From Why It Still Sucks Today Control versus Ease of Use I Don’t Care How Your Program Works A Bad Feature and a Good One Stopping the Proceedings with Idiocy Testing on Live Animals Where We Are and What You Can Do Chapter 2: Tangled in the Web Where We Came From How It Works Why It Still Sucks Today Client-Centered Design versus Server-Centered Design Where’s My Eye Opener? It’s Obvious—Not! Splash, Flash, and Animation Testing on Live Animals What You Can Do about It Chapter 3: Keep Me Safe The Way It Was Why It Sucks Today What Programmers Need to Know, but Don’t A Human Operation Budgeting for Hassles Users Are Lazy Social Engineering Last Word on Security What You Can Do Chapter 4: Who the Heck Are You? Where We Came From Why It Still Sucks Today Incompatible Requirements OK, So Now What? Chapter 5: Who’re You Looking At? Yes, They Know You Why It Sucks More Than Ever Today Users Don’t Know Where the Risks Are What They Know First Milk You with Cookies? Privacy Policy Nonsense Covering Your Tracks The Google Conundrum Solution Chapter 6: Ten Thousand Geeks, Crazed on Jolt Cola See Them in Their Native Habitat All These Geeks Who Speaks, and When, and about What Selling It The Next Generation of Geeks—Passing It On Chapter 7: Who Are These Crazy Bastards Anyway? Homo Logicus Testosterone Poisoning Control and Contentment Making Models Geeks and Jocks Jargon Brains and Constraints Seven Habits of Geeks Chapter 8: Microsoft: Can’t Live With ’Em and Can’t Live Without ’Em They Run the World Me and Them Where We Came From Why It Sucks Today Damned if You Do, Damned if You Don’t We Love to Hate Them Plus ça Change Growing-Up Pains What You Can Do about It The Last Word Chapter 9: Doing Something About It 1. Buy 2. Tell 3. Ridicule 4. Trust 5. Organize Epilogue About the Author

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  • Learning libraries without books or tutorials

    - by Kawili-wili
    While many ask questions about where to find good books or tutorials, I'd like to take the opposite tack. I consider myself to be an entry-level programmer ready to move up to mid-level. I have written code in c, c++, c#, perl, python, clojure, vb, and java, so I'm not completely clueless. Where I see a problem in moving to the next level is learning to make better use of the literally hundreds upon hundreds of libraries available out there. I seem paralyzed unless there is a specific example in a book or tutorial to hand-hold me, yet I often read in various forums where another programmer attempts to assist with a question. He/she will look through the docs or scan the available classes/methods in their favorite IDE and seem to grok what's going on in a relatively short period of time, even if they had no previous experience with that specific library or function. I yearn to break the umbilical chord of constantly spending hour upon hour searching and reading, searching and reading, searching and reading. Many times there is no book or tutorial, or if there is, the discussion glosses over my specific needs or the examples shown are too far off the path for the usage I had in mind or the information is outdated and makes use of deprecated components or the library itself has fallen out of mainstream, yet is still perfectly usable (but no docs, books, or tutorials to hand-hold). My question is: In the absence of books or tutorials, what is the best way to grok new or unfamiliar libraries? I yearn to slicken the grok path so I can get down to the business of doing what I love most -- coding.

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  • SQL Server 2008, Books Online, and old documentation...

    - by Chris J
    [I have no idea if stackoverflow really is right right place for this, but don't know how many devs on here run into msi issues with SQL Server; suggest SuperUser or ServerFault if folk think it's better on either of those] About a year ago, when we were looking at moving our codebase forward and migrating to SQL Server 2008, I pulled down a copy of Books Online from the MSDN. Reviewed, did background research, fed results upstream, grabbed Express and tinkered with that. Then we got the nod to move forward (hurrah!) this past couple of weeks. So armed with Developer Edition, and running through the install, I've since found out I've zapped the Books Online MSI, no-ones got a copy of it, and Microsoft only have a later version (Oct 2009) available, so damned if I can update my SQL Server fully and properly... {mutter grumble}. Does anyone know if old versions of Books Online are available for download anywhere? Poking around the Microsoft download centre can't find it, neither is my google-fu finding it. For reference, I'm looking for SQLServer2008_BOL_August2008_ENU.msi ... This may just be a case of good ol' manual delete the files and (try) and clean up the registry :-(

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  • Layman's book for understanding computer networks

    - by srid
    The good thing about books targeting a layman is that it is usually very engaging to read (not dry and boring like, say, school/university books). Charles Petzold's Code: The Hidden Language of Computer Hardware and Software does this for explaining the underlying hardware in computers. Is there a similar book for understanding computer networking?

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  • Business/Development Liaison Wanting To Enhance Understanding In Programming

    - by James Alexander
    I lead software development for a team of of about 20 devs and we're primarily a .net/sql server shop. We've recently created a new role in our organization for a more business like role to assist in prioritization of development and this business liaison has asked me if there are any books or resources he could use to better understand software concepts in a meaningful way. Any suggestions or advice would be greatly appreciated.

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