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  • sendto: Invalid Argument

    - by Sylvain
    Hi, I have a list<struct sockaddr_in> _peers I'd like to use for sendto() the list is filled this way struct hostent *hp; hp = gethostbyname(hostname); sockaddr_in sin; bzero(&sin, sizeof(sin)); sin.sin_family = AF_INET; sin.sin_port = htons(port); sin.sin_addr.s_addr = *(in_addr_t *)hp->h_addr; _peers.push_front(sin); and here's how I try to send: for (list<struct sockaddr_in>::iterator it = _peers.begin(); it != _peers.end(); ++it) { if (sendto(_s, "PING", 5, 0, (struct sockaddr *)&(*it), sizeof(struct sockaddr_in)) < 0) perror("sendto"); } outputs: sendto: Invalid argument If I create the struct sockaddr_in right before sendto(), everything works fine, so I guess I fail at using the list properly ... I also tested using &_peers.front() directly and still get the same error ... what am I doing wrong? Thanks in advance,

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  • Create a VPN with Python

    - by user213060
    I want to make a device "tunnel box" that you plug an input ethernet line, and an output ethernet line, and all the traffic that goes through it gets modified in a special way. This is similar to how a firewall, IDS, VPN, or similar boxes are connected inline in a network. I think you can just assume that I am writing a custom VPN in Python for the purpose of this question: LAN computer <--\ LAN computer <---> [LAN switch] <--> ["tunnel box"] <--> [internet modem] <--> LAN computer <--/ My question is, what is a good way to program this "tunnel box" from python? My application needs to see TCP flows at the network layer, not as individual ethernet frames. Non-TCP/IP traffic such as ICPM and other types should just be passed through. Example Twisted-like Code for my "tunnel box" tunnel appliance: from my_code import special_data_conversion_function class StreamInterceptor(twisted.Protocol): def dataReceived(self,data): data=special_data_conversion_function(data) self.outbound_connection.send(data) My initial guesses: TUN/TAP with twisted.pair.tuntap.py - Problem: This seems to only work at the ethernet frame level, not like my example? Socks proxy - Problem: Not transparent as in my diagram. Programs have to be specifically setup for it. Thanks!

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  • OT: US Banks: Bank Routing Number and BIC/SWIFT

    - by Konerak
    I know it is a bit offtopic, but I've been having a hard time finding more information to this question, and since this site is visited by a lot of people from the United States, you guys might know/find the answer more easily. Banks in europe each have a SWIFT Number, while US Banks use Routing Numbers. This leads to following questions: Does each bank in the US also carry a BIC number? (SWIFT) Is there a 1-1 relationship between BIC and SWIFT? Is there a list of these numbers somewhere? (background information: we're adding international payments to our bookkeeping application. Users can add international suppliers, but my boss prefered not to change the current supplier table but to have the ROUTING NUMBER in another table, with as PK the BIC. I'm wondering if BIC is a valid choice, or if it should just be BANK ACCOUNT NUMBER.)

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  • cartesian product

    - by John Retallack
    I've been trying to do a function that returns the Cartesian Product of n sets,in Dr Scheme,the sets are given as a list of lists,I've been stuck at this all day,I would like a few guidelines as where to start,I've wrote a pice of code but it dosen't work. (define cart-n(?(l) (if (null? l) '(()) (map (?(lst) (cons (car ( car(l))) lst)) (cart-n (cdr l) )))))

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  • Linq Query Performance , comparing Compiled query vs Non-Compiled.

    - by AG.
    Hello Guys, I was wondering if i extract the common where clause query into a common expression would it make my query much faster, if i have say something like 10 linq queries on a collection with exact same 1st part of the where clause. I have done a small example to explain a bit more . public class Person { public string First { get; set; } public string Last { get; set; } public int Age { get; set; } public String Born { get; set; } public string Living { get; set; } } public sealed class PersonDetails : List<Person> { } PersonDetails d = new PersonDetails(); d.Add(new Person() {Age = 29, Born = "Timbuk Tu", First = "Joe", Last = "Bloggs", Living = "London"}); d.Add(new Person() { Age = 29, Born = "Timbuk Tu", First = "Foo", Last = "Bar", Living = "NewYork" }); Expression<Func<Person, bool>> exp = (a) => a.Age == 29; Func<Person, bool> commonQuery = exp.Compile(); var lx = from y in d where commonQuery.Invoke(y) && y.Living == "London" select y; var bx = from y in d where y.Age == 29 && y.Living == "NewYork" select y; Console.WriteLine("All Details {0}, {1}, {2}, {3}, {4}", lx.Single().Age, lx.Single().First , lx.Single().Last, lx.Single().Living, lx.Single().Born ); Console.WriteLine("All Details {0}, {1}, {2}, {3}, {4}", bx.Single().Age, bx.Single().First, bx.Single().Last, bx.Single().Living, bx.Single().Born); So can some of the guru's here give me some advice if it would be a good practice to write query like var lx = "Linq Expression " or var bx = "Linq Expression" ? Any inputs would be highly appreciated. Thanks, AG

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  • Microsoft Quotation

    - by Asad Jibran Ahmed
    I don't know if this is the right place to ask this question, but I honestly have exhausted my self searching for the last hour. I am looking for a quotation made about Microsofts software. It goes something along the lines of: "They may make 2nd grade crappy software, but by God they know how to design interfaces" It was by a somewhat popular open source personality about the lack of good interface design in open source software. Does any one know the exact quotation? It will be a great help if someone can point me in the right direction.

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  • Data Transfer Objects VS Domain/ActiveRecord Entities in the View in RoR

    - by leypascua
    I'm coming from a .NET background, where it is a practice to not bind domain/entity models directly to the view in not-so-basic CRUD-ish applications where the view does not directly project entity fields as-is. I'm wondering what's the practice in RoR, where the default persistence mechanism is ActiveRecord. I would assert that presentation-related info should not be leaked to the entities, not sure though if this is how real RoR heads would do it. If DTOs/model per view is the approach, how will you do it in Rails? Your thoughts? EDIT: Some examples: - A view shows a list of invoices, with the number of unique items in one column. - A list of credit card accounts, where possibly fraudulent transactions were executed. For that, the UI needs to show this row in red. For both scenarios, The lists don't show all of the fields of the entities, just a few to show in the list (like invoice #, transaction date, name of the account, the amount of the transaction) For the invoice example, The invoice entity doesn't have a field "No. of line items" mapped on it. The database has not been denormalized for perf reasons and it will be computed during query time using aggregate functions. For the credit card accounts example, surely the card transaction entity doesn't have a "Show-in-red" or "IsFraudulent" invariant. Yes it may be a business rule, but for this example, that is a presentation concern, so I would like to keep it out of my domain model.

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  • Recommended Math textbooks for programmers

    - by Tony
    I learned math in a non-English environment, I recently read some books about algorithm analysis, I found some math concepts were confusing, and seemed not the same as what I've learned. What math textbooks would you recommend that covers math concepts from the scratch and suitable for self-learning ?

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  • Corrupted version of WordPad [closed]

    - by Mike GH
    Somehow in trying to cleanup my computer's hard drive, I have inadvertently corrupted WordPad, which I have long used for viewing many types of files, including logs (i.e., log4j). Now when I right click one of these files and choose "open with" & WordPad, I get an error (fn is not a valid Win32 application). I've researched this issue, tried reinstalling wordpad.exe; bbut I still get the same error. Any suggestions would be appreciated.

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  • SNMP Broadcast on Windows

    - by SNMP Dev
    I'm writing an SNMP agent in windows. The agent responds fine simple get and get-next request sent directly to computer's ip address. But when I do a SNMP broadcast, the computer receives the packet but does not anwer that. Why is that? The firewall is off and the antivirus too.

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  • Is the IP from the source or target in this System.Net.Sockets.SocketException?

    - by Jeremy Mullin
    I'm making an outbound connection using a DNS name to a server other than the localhost, and I get this exception: System.Net.WebException: Unable to connect to the remote server --- System.Net.Sockets.SocketException: No connection could be made because the target machine actively refused it 127.0.0.1:5555 The text implies that the TARGET machine refused the connection, but the IP address and port are from the localhost, which is kind of confusing. So is that IP address really the outgoing IP and port, even though the exception was caused by the target refusing the connection? Or is the exception from the local firewall blocking the outgoing connection?

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  • Boost Thread Specific Storage Question (boost/thread/tss.hpp)

    - by Hassan Syed
    The boost threading library has an abstraction for thread specific (local) storage. I have skimmed over the source code and it seems that the TSS functionality can be used in an application with any existing thread regardless of weather it was created from boost::thread --i.e., this implies that certain callbacks are registered with the kernel to hook in a callback function that may call the destructor of any TSS objects when the thread or process is going out of scope. I have found these callbacks. I need to cache HMAC_CTX's from OpenSSL inside the worker threads of various web-servers (see this, detailed, question for what I am trying to do), and as such I do not controll the life-time of the thread -- the web-server does. Therefore I will use the TSS functionality on threads not created by boost::thread. I just wanted to validate my assumptions before I started implementing the caching logic, are there any flaws in my logic ?

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  • Scalaz Kleisli question

    - by oxbow_lakes
    There is a trait called Kleisli in the scalaz library. Looking at the code: import scalaz._ import Scalaz._ type StringPair = (String, String) val f: Int => List[String] = (i: Int) => List((i |+| 1).toString, (i |+| 2).toString) val g: String => List[StringPair] = (s: String) => List("X" -> s, s -> "Y") val k = kleisli(f) >=> kleisli(g) //this gives me a function: Int => List[(String, String)] Calling the function k with the value of 2 gives: println( k(2) ) //Prints: List((X,3), (3,Y), (X,4), (4,Y)) My question is: how would I use Scalaz to combine f and g to get a function m such that the output of m(2) would be: val m = //??? some combination of f and g println( m(2) ) //Prints: List((X,3), (X,4), (3,Y), (4,Y)) Is this even possible?

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  • C# StreamReader.EndOfStream produces IOException

    - by Ziplin
    I'm working on an application that accepts TCP connections and reads in data until an </File> marker is read and then writes that data to the filesystem. I don't want to disconnect, I want to let the client sending the data to do that so they can send multiple files in one connection. I'm using the StreamReader.EndOfStream around my outter loop, but it throws an IOException when the client disconnects. Is there a better way to do this? private static void RecieveAsyncStream(IAsyncResult ar) { TcpListener listener = (TcpListener)ar.AsyncState; TcpClient client = listener.EndAcceptTcpClient(ar); // init the streams NetworkStream netStream = client.GetStream(); StreamReader streamReader = new StreamReader(netStream); StreamWriter streamWriter = new StreamWriter(netStream); while (!streamReader.EndOfStream) // throws IOException { string file= ""; while (file!= "</File>" && !streamReader.EndOfStream) { file += streamReader.ReadLine(); } // write file to filesystem } listener.BeginAcceptTcpClient(RecieveAsyncStream, listener); }

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  • Scalaz: request for use case for Cokleisli composition

    - by oxbow_lakes
    This question isn't meant as flame-bait! As it might be apparent, I've been looking at Scalaz recently. I'm trying to understand why I need some of the functionality that the library provides. Here's something: import scalaz._ import Scalaz._ type NEL[A] = NonEmptyList[A] val NEL = NonEmptyList I put some println statements in my functions to see what was going on (aside: what would I have done if I was trying to avoid side effects like that?). My functions are: val f: NEL[Int] => String = (l: NEL[Int]) => {println("f: " + l); l.toString |+| "X" } val g: NEL[String] => BigInt = (l: NEL[String]) => {println("g: " + l); BigInt(l.map(_.length).sum) } Then I combine them via a cokleisli and pass in a NEL[Int] val k = cokleisli(f) =>= cokleisli(g) println("RES: " + k( NEL(1, 2, 3) )) What does this print? f: NonEmptyList(1, 2, 3) f: NonEmptyList(2, 3) f: NonEmptyList(3) g: NonEmptyList(NonEmptyList(1, 2, 3)X, NonEmptyList(2, 3)X, NonEmptyList(3)X) RES: 57 The RES value is the character count of the (String) elements in the final NEL. Two things occur to me: How could I have known that my NEL was going to be reduced in this manner from the method signatures involved? (I wasn't expecting the result at all) What is the point of this? Can a reasonably simple and easy-to-follow use case be distilled for me? This question is a thinly-veiled plea for some lovely person like retronym to explain how this powerful library actually works.

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  • Yahoo Pipes: filter items in a feed based on words in a text file

    - by pufferfish
    I have a pipe that filters an RSS feed and removes any item that contains "stopwords" that I've chosen. Currently I've manually created a filter for each stopword in the pipe editor, but the more logical way is to read these from a file. I've figured out how to read the stopwords out of the text file, but how do I apply the filter operator to the feed, once for every stopword? The documentation states explicitly that operators can't be applied within the loop construct, but hopefully I'm missing something here.

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  • A/UX cc compiler errors on trivial code: "declared argument argc is missing"

    - by Fzn
    On a quite ancient UNIX (Apple A/UX 3.0.1 for 680x0 processors) using the built-in c compiler (cc), this issue arrises. Here is the code I'm trying to compile: #include <stdlib.h> #include <stdio.h> int main() int argc; char **argv; { if (argc > 1) puts(argv[1]); return (EXIT_SUCCESS); } And here is the output I get: pigeonz.root # cc -c test.c "test.c", line 5: declared argument argc is missing "test.c", line 6: declared argument argv is missing Using a more modern prototype did not help, nor did the manual page, nor a quick google search. What am I doing wrong?

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  • Don't understand the typing of Scala's delimited continuations (A @cps[B,C])

    - by jkff
    I'm struggling to understand what precisely does it mean when a value has type A @cps[B,C] and what types of this form should I assign to my values when using the delimited continuations facility. I've looked at some sources: http://lamp.epfl.ch/~rompf/continuations-icfp09.pdf http://www.scala-lang.org/node/2096 http://dcsobral.blogspot.com/2009/07/delimited-continuations-explained-in.html http://blog.richdougherty.com/2009/02/delimited-continuations-in-scala_24.html but they didn't give me much intuition into this. In the last link, the author tries to give an explicit explanation, but it is not clear enough anyway. The A here represents the output of the computation, which is also the input to its continuation. The B represents the return type of that continuation, and the C represents its "final" return type—because shift can do further processing to the returned value and change its type. I don't understand the difference between "output of the computation", "return type of the continuation" and "final return type of the continuation". They sound like synonyms.

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  • J: Self-reference in bubble sort tacit implementation

    - by Yasir Arsanukaev
    Hello people! Since I'm beginner in J I've decided to solve a simple task using this language, in particular implementing the bubblesort algorithm. I know it's not idiomatically to solve such kind of problem in functional languages, because it's naturally solved using array element transposition in imperative languages like C, rather than constructing modified list in declarative languages. However this is the code I've written: (((<./@(2&{.)), $:@((>./@(2&{.)),2&}.)) ^: (1<#)) ^: # Let's apply it to an array: (((<./@(2&{.)), $:@((>./@(2&{.)),2&}.)) ^: (1<#)) ^: # 5 3 8 7 2 2 3 5 7 8 The thing that confuses me is $: referring to the statement within the outermost parentheses. Help says that: $: denotes the longest verb that contains it. The other book (~ 300 KiB) says: 3+4 7 5*20 100 Symbols like + and * for plus and times in the above phrases are called verbs and represent functions. You may have more than one verb in a J phrase, in which case it is constructed like a sentence in simple English by reading from left to right, that is 4+6%2 means 4 added to whatever follows, namely 6 divided by 2. Let's rewrite my code snippet omitting outermost ()s: ((<./@(2&{.)), $:@((>./@(2&{.)),2&}.)) ^: (1<#) ^: # 5 3 8 7 2 2 3 5 7 8 Reuslts are the same. I couldn't explain myself why this works, why only ((<./@(2&{.)), $:@((>./@(2&{.)),2&}.)) ^: (1<#) is treated as the longest verb for $: but not the whole expression ((<./@(2&{.)), $:@((>./@(2&{.)),2&}.)) ^: (1<#) ^: # and not just (<./@(2&{.)), $:@((>./@(2&{.)),2&}.), because if ((<./@(2&{.)), $:@((>./@(2&{.)),2&}.)) ^: (1<#) is a verb, it should also form another verb after conjunction with #, i. e. one might treat the whole sentence (first snippet) as a verb. Probably there's some limit for the verb length limited by one conjunction. Look at the following code (from here): factorial =: (* factorial@<:) ^: (1&<) factorial 4 24 factorial within expression refers to the whole function, i. e. (* factorial@<:) ^: (1&<). Following this example I've used a function name instead of $:: bubblesort =: (((<./@(2&{.)), bubblesort@((>./@(2&{.)),2&}.)) ^: (1<#)) ^: # bubblesort 5 3 8 7 2 2 3 5 7 8 I expected bubblesort to refer to the whole function, but it doesn't seem true for me since the result is correct. Also I'd like to see other implementations if you have ones, even slightly refactored. Thanks.

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  • Python: unix socket -> broken pipe

    - by Heinrich Schmetterling
    I'm trying to get Python socket working as an alternative to calling the command line socat. This socat command works fine: echo 'cmd' | sudo socat stdio <path-to-socket> but when I run this python code, I get an error: >>> import socket >>> s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) >>> s.connect(<path-to-socket>) >>> s.send('cmd') Traceback (most recent call last): File "<stdin>", line 1, in <module> socket.error: (32, 'Broken pipe') Any ideas what the issue is? Thanks.

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