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  • What Design Pattern is this?

    - by 01
    I know that everything we do in programming can be described as design pattern(even abstract method has design pattern called template method) public class Guicer extends AbstractModule { private static Injector injector = Guice.createInjector(new Guicer()); public static void setInjector(Injector injector) { Guicer.injector = injector; } public static T getInstance(Class c) { return injector.getInstance(c); } @Override protected void configure() { } } What design patterns are used in this code?

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  • What host do I have to bind a listening socket to?

    - by herrturtur
    I used python's socket module and tried to open a listening socket using import socket import sys def getServerSocket(host, port): for r in socket.getaddrinfo(host, port, socket.AF_UNSPEC, socket.SOCK_STREAM, 0, socket.AI_PASSIVE): af, socktype, proto, canonname, sa = r try: s = socket.socket(af, socktype, proto) except socket.error, msg: s = None continue try: s.bind(sa) s.listen(1) except socket.error, msg: s.close() s = None continue break if s is None: print 'could not open socket' sys.exit(1) return s Where host was None and port was 15000. The program would then accept connections, but only from connections on the same machine. What do I have to do to accept connections from the internet?

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  • .net configurable business error messages

    - by Daniel
    Hi all, I need to implement some kind of solution such that in our business logic layer when certain conditions are met an error message is returned. That error message should be configurable either in a file or table that can be edited at run time if needed. I've seen it done before a few ways and it always ends up something like "This error message is {0}" and then when the dev goes the use the message they dont neccesarily know how many (if any) parameters the message needs. Just hoping to leverage off something that may have already been done, I dont think there is a provider or anything already in the .net framework.

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  • Using LINQ, need help splitting a byte array on data received from Silverlight sockets

    - by gcadmes
    The message packats received contains multiple messages deliniated by a header=0xFD and a footer=0xFE // sample message packet with three // different size messages List<byte> receiveBuffer = new List<byte>(); receiveBuffer.AddRange(new byte[] { 0xFD, 1, 2, 0xFE, 0xFD, 1, 2, 3, 4, 5, 6, 7, 8, 0xFE, 0xFD, 33, 65, 25, 44, 0xFE}); // note: this sample code is without synchronization, // statements, error handling...etc. while (receiveBuffer.Count > 0) { var bytesInRange = receiveBuffer.TakeWhile(n => n != 0xFE); foreach (var n in bytesInRange) Console.WriteLine(n); // process message.. // 1) remove bytes read from receive buffer // 2) construct message object... // 3) etc... receiveBuffer.RemoveRange(0, bytesInRange.Count()); } As you can see, (including header/footer) the first message in this message packet contains 4 bytes, and the 2nd message contains 10 bytes,a and the 3rd message contains 6 bytes. In the while loop, I was expecting the TakeWhile to add the bytes that did not equal the footer part of the message. Note: Since I am removing the bytes after reading them, the header can always be expected to be at position '0'. I searched examples for splitting byte arrays, but non demonstrated splitting on arrays of unknown and fluctuating sizes. Any help will be greatly appreciated. thanks much!

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  • Avoiding sub-type selection in view code

    - by John Donoghue
    Hi, I have some code where the model contains some classes like (vb.net pseudocode, but could be any OO language): Enum AttributeType Boolean Date String End Enum MustInherit Class Attibute Must Override Function Type As AttributeType End Class Class BooleanAttribute: Attribute Function Type As AttributeType Return AttributeType.Boolean End Function End Class And the view contains some code like: Select Case AttributeType Case Boolean //Display checkbox control Case Date //Display date picker control Case String //Display textbox control End Select I don't really like the code in the view, for the hopefully obvious reasons (what happens when I get a new attribute type etc). My question is, how should I replace it? I could easily add a method to the concrete classes, but that pollutes the model with UI stuff so that's a horrible idea. I could move the select into a factory, but that seems to be just hiding the problem. Can anybody advise a better approach?

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  • What is the best businessmodel when using NHibernate to access the database?

    - by Sem Dendoncker
    Hi, I'm starting to use NHiberante as a dataaccess tier. I'm used to work with the repository model as a business model. This means, my domain model (not really a tier), my asp.net application tier, my repository tier which finally uses my dataaccess tier. But with what I've learned by now (on NHibernate) I know that many logic is done within an ISession so I was wondering if NHibernate could be used within the repository tier. Or perhaps there are even better ways to use NHibernate. Does anyone know where I could find a propriate example of how to use NHibernate in an webapplication? Cheers, M.

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  • Testing for a closed socket

    - by Robert S. Barnes
    I'm trying to test for a closed socket that has been gracefully closed by the peer without incurring the latency hit of a double send to induce a SIGPIPE. One of the assumptions here is that the socket if closed was gracefully closed by the peer immediately after it's last write / send. Actual errors like a premature close are dealt with else where in the code. If the socket is still open, there will be 0 or more bytes data which I don't actually want to pull out of the socket buffer yet. I was thinking that I could call int ret = recv(sockfd, buf, 1, MSG_DONTWAIT | MSG_PEEK); to determine if the socket is still connected. If it's connected but there's no data in the buffer I'll get a return of -1 with errno == EAGAIN and return the sockfd for reuse. If it's been gracefully closed by the peer I'll get ret == 0 and open a new connection. I've tested this and it seems to work. However, I suspect there is a small window between when I recv the last bit of my data and when the peer FIN arrives in which I could get a false-positive EAGAIN from my test recv. Is this going to bite me, or is there a better way of doing this?

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  • What do I need to know before working on an IM application?

    - by John
    I'm looking into building an IM-type application using Java stack (for the server at least). I'd be interested to see any information/advice on how applications like Skype/AIM/MSN work, as well as know any technologies/APIs that might be relevant. Without giving away the idea itself, it's perhaps more akin to Google Wave than Skype, but information useful for either is very welcome. Specific points I have already thought of include: Server Vs P2P... for reasons of logging my system will require all communication to go through a central server. Is this how other IM tools work... especially when audio/video comes into the equation? Cross-communication with other systems. Are there APIs for this or do all IM providers work hard to keep their protocol secret? The nature of what I'm designing means integration could probably only be limited, but it definitely seems worthwhile from a business perspective

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  • What does it mean when a ByteInputStream keeps returning 0?

    - by Zombies
    I have a ByteInputStream, created from a Socket in Java. The connection is to a simple web server that uses chunked transfer encoding. The web server does in fact work in normal browser. But in my program, I am attempting to read, I read the first first bytes (some 5kb of data). But each read after that returns 0 bytes read. Isn't it supposed to block until it can read?

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  • What books should be read to become an excelent software architect.

    - by dev-cu
    I know there are good books to start with, but let's make a short list of 3-5 books, i don't think only one book could help you in the way of becoming a good architect. I read some time ago that an architect takes years to have the knowledge and the ability to make good decisions. Suppose someone has the potential, what is the way? Please, answers with books that doesn't repeat over the same theme, making your learning process widely. One short list per answer. Vote up that you think are the best ones. Thanks.

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  • twisted .loseConnection does not immediately lose connection?

    - by Claudiu
    I have a server with a few clients connected to it. When CTRL+C is hit (that is, reactor starts shutting down), I want to close all my connections, wait until they are cleanly closed, and then stop. I do this by going through the connected clients' transports and calling .loseConnection(). On the ones that are connected locally, they immediately disconnect. However, on one that is connected through the internet, the connection is not immediately lost. Communication stops - and closing the client program no longer even tells the server that the connection has died, although it does before calling .loseConnection() - but the connection is not deemed 'lost' until a few minutes later after I send a few heartbeat requests from the server. I understand that if a connection dies, there's no way for the server to know unless it tries to send some data. But if I specifically ask for a connection to be closed, why does it not just close/disconnect immediately? Am I calling the wrong function?

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  • Where should I handle the exceptions, in the BLL, DAL or PL ?

    - by Puneet Dudeja
    Which is the best place to handle the exceptions ? BLL, DAL or PL ? Should I allow the methods in the DAL and BLL to throw the exceptions up the chain and let the PL handle them? or should I handle them at the BLL ? e.g If I have a method in my DAL that issues "ExecuteNonQuery" and updates some records, and due to one or more reason, 0 rows are affected. Now, how should I let my PL know that whether an exception happened or there really was no rows matched to the condition. Should I use "try catch" in my PL code and let it know through an exception, or should I handle the exception at DAL and return some special code like (-1) to let the PL differentiate between the (exception) and (no rows matched condition i.e. zero rows affected) ?

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  • How to reduce latency of data sent through a REST api

    - by Sid
    I have an application which obtains data in JSON format from one of our other servers. The problem I am facing is, there is is significant delay when when requesting for this information. Since a lot of data is passed (approx 1000 records per request where each record is pretty huge) is there a way that compression would help reducing the speed. If so which compression scheme would you recommend. I read on another thread that they pattern of data also matters a lot on they type of compression that needs to be used. The pattern of data is consistent and resembles the following :desc=>some_description :url=>some_url :content=>some_content :score=>some_score :more_attributes=>more_data Can someone recommend a solution to how I could reduce this delay. They delay is approx 6-8 seconds. I'm using Ruby on Rails to develop this application and the server providing the data uses Python for the most part.

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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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  • Sequential WSASend() calls - can I rely on TCP to put them on the wire in the posting order?

    - by Poni
    On Windows I/O completion ports, say I do this: void function() { WSASend("1111"); // A WSASend("2222"); // B WSASend("3333"); // C } If I got a "write-complete" that says 3 bytes of WSASend() A were sent, is it possible that right after that I'll get a "write-complete" that tells me that some or all of B & C were sent, or will TCP will hold them until I re-issue a WSASend() call with the rest of A's data? Or will TCP complete it automatically?

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  • Abstract away a compound identity value for use in business logic?

    - by John K
    While separating business logic and data access logic into two different assemblies, I want to abstract away the concept of identity so that the business logic deals with one consistent identity without having to understand its actual representation in the data source. I've been calling this a compound identity abstraction. Data sources in this project are swappable and various and the business logic shouldn't care which data source is currently in use. The identity is the toughest part because its implementation can change per kind of data source, whereas other fields like name, address, etc are consistently scalar values. What I'm searching for is a good way to abstract the concept of identity, whether it be an existing library, a software pattern or just a solid good idea of some kind is provided. The proposed compound identity value would have to be comparable and usable in the business logic and passed back to the data source to specify records, entities and/or documents to affect, so the data source must be able to parse back out the details of its own compound ids. Data Source Examples: This serves to provide an idea of what I mean by various data sources having different identity implementations. A relational data source might express a piece of content with an integer identifier plus a language specific code. For example. content_id language Other Columns expressing details of content 1 en_us 1 fr_ca The identity of the first record in the above example is: 1 + en_us However when a NoSQL data source is substituted, it might somehow represent each piece of content with a GUID string 936DA01F-9ABD-4d9d-80C7-02AF85C822A8 plus language code of a different standardization, And a third kind of data source might use just a simple scalar value. So on and so forth, you get the idea.

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  • Handling multiple post-defined datasource connections based on user

    - by choudeshell
    How should I handle multiple user-connection defined datasource connection in my .NET application? To illustrate this better; the user provides three (3) pieces of information, username, password and data source name. This data source name is then looked-up in a central database telling that application which main database this user should connect to. My question is, in the DataAccess layer, should we only pass down enough information to uniquely identify that user, and query the central database each time in the DAL; or, should we provide another way to pass the datasource connection down to the DAL?

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