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  • Buffer management for socket application best practice

    - by Poni
    Having a Windows IOCP app............ I understand that for async i/o operation (on network) the buffer must remain valid for the duration of the send/read operation. So for each connection I have one buffer for the reading. For sending I use buffers to which I copy the data to be sent. When the sending operation completes I release the buffer so it can be reused. So far it's nice and not of a big issue. What remains unclear is how do you guys do this? Another thing is that even when having things this way, I mean multi-buffers, the receiver side might be flooded (talking from experience) with data. Even setting SO_RCVBUF to 25MB didn't help in my testings. So what should I do? Have a to-be-sent queue?

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  • Detecting I/O errors in a NON BLOCKING SOCKET

    - by ripunjay-tripathi-gmail-com
    I am writing a client - server system in which I used NON-BLOCKING sockets. My problem is to detect error { while performing send() or write() } that may occur while data transfer. Example lets say, while the data is being transferred the peer crashes. Another case there is some network problem, something like wire unplugged etc. As of now, I am using a high level ACK, that peer sends after receiving the complete data. Ripunjay Tripathi

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  • method to find my UDP socket's "real" port?

    - by yairchu
    Is there any free service to which I could send a UDP packet and it would respond telling me what is my "real" UDP port? (my application is behind a NAT) This kind of service could allow me to make a p2p coordination server with normal php hosting. The p2p clients would know their UDP ports from this service They will then contact my server over HTTP (which is what regular web hosting allows) and tell it their port (and ip, which is normally supplied to cgi scripts) My server will give the clients the IP addresses and ports of the other clients.

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  • C socket programming: client send() but server select() doesn't see it

    - by Fantastic Fourier
    Hey all, I have a server and a client running on two different machines where the client send()s but the server doesn't seem to receive the message. The server employs select() to monitor sockets for any incoming connections/messages. I can see that when the server accepts a new connection, it updates the fd_set array but always returns 0 despite the client send() messages. The connection is TCP and the machines are separated by like one router so dropping packets are highly unlikely. I have a feeling that it's not select() but perhaps send()/sendto() from client that may be the problem but I'm not sure how to go about localizing the problem area. while(1) { readset = info->read_set; ready = select(info->max_fd+1, &readset, NULL, NULL, &timeout); } above is the server side code where the server has a thread that runs select() indefinitely. rv = connect(sockfd, (struct sockaddr *) &server_address, sizeof(server_address)); printf("rv = %i\n", rv); if (rv < 0) { printf("MAIN: ERROR connect() %i: %s\n", errno, strerror(errno)); exit(1); } else printf("connected\n"); sleep(3); char * somemsg = "is this working yet?\0"; rv = send(sockfd, somemsg, sizeof(somemsg), NULL); if (rv < 0) printf("MAIN: ERROR send() %i: %s\n", errno, strerror(errno)); printf("MAIN: rv is %i\n", rv); rv = sendto(sockfd, somemsg, sizeof(somemsg), NULL, &server_address, sizeof(server_address)); if (rv < 0) printf("MAIN: ERROR sendto() %i: %s\n", errno, strerror(errno)); printf("MAIN: rv is %i\n", rv); and this is the client side where it connects and sends messages and returns connected MAIN: rv is 4 MAIN: rv is 4 any comments or insightful insights are appreciated.

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  • Programming With Markov Algorithms.

    - by Bubba88
    Hello! I Wonder if someone has used Markov Algorithm-based programming system or embedded facility in production or for scientific purpose. I know about 'REFAL' programming language invented a thousand years ago, but it all seems to be dead, so.. Ref: http://en.wikipedia.org/wiki/Markov_algorithm

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  • Any learning/studying material for C/C++ that use game programming as learning context out there?

    - by mac
    As most of game programming is done - I read on this very site - in C/C++ I was wondering if there is any learning/studying material for C/C++ that would target specifically game programming. I am not looking for material about "developing games" or "software architecture for games", but rather for material that uses "game programming" as the CONTEXT for introducing and illustrating C/C++ features, idioms, programming techniques, etc... With a simile: think to the GOF book on design patterns. There, they used "developing a text-editor" as a context for introducing design patterns, but the book is most definitively not a book about "developing text-editors". Thanks in advance for your time and advice! PS: My background: I am a programmer with a solid experience in OO scripting languages and only some experience in C and Assembler (on AVR microcontrollers), so I am thinking to mid-to-advanced level material, rather than tutorials for beginners, although it might be interesting to take a look to the latter ones if nothing else is available.

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  • Canonical pattern reference in Actors programming model.

    - by Bubba88
    Hello! Is there a source, which I could use to learn some of the most used and popular practices regarding Actor-/Agent-oriented programming. My primary concern is about parallelism and distribution limited to the mentioned scheme - Actors, message passing. Should I begin with Erlang documentation or maybe there is any kind of book that describes the most important building blocks when programming Actor-oriented? Thank you! (Most useful examples would be in Scala or F#)

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  • Boost Asio UDP retrieve last packet in socket buffer

    - by Alberto Toglia
    I have been messing around Boost Asio for some days now but I got stuck with this weird behavior. Please let me explain. Computer A is sending continuos udp packets every 500 ms to computer B, computer B desires to read A's packets with it own velocity but only wants A's last packet, obviously the most updated one. It has come to my attention that when I do a: mSocket.receive_from(boost::asio::buffer(mBuffer), mEndPoint); I can get OLD packets that were not processed (almost everytime). Does this make any sense? A friend of mine told me that sockets maintain a buffer of packets and therefore If I read with a lower frequency than the sender this could happen. ¡? So, the first question is how is it possible to receive the last packet and discard the ones I missed? Later I tried using the async example of the Boost documentation but found it did not do what I wanted. http://www.boost.org/doc/libs/1_36_0/doc/html/boost_asio/tutorial/tutdaytime6.html From what I could tell the async_receive_from should call the method "handle_receive" when a packet arrives, and that works for the first packet after the service was "run". If I wanted to keep listening the port I should call the async_receive_from again in the handle code. right? BUT what I found is that I start an infinite loop, it doesn't wait till the next packet, it just enters "handle_receive" again and again. I'm not doing a server application, a lot of things are going on (its a game), so my second question is, do I have to use threads to use the async receive method properly, is there some example with threads and async receive? Thanks for you attention.

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  • How can I know if programming is right for me?

    - by user66414
    I have an IT background and was pretty confident until an opportunity came up at work to go into programming(C#). I have never programmed before this, and the software I am programming for is a program I have never used before (a 3D modeling software). It has been 6 months since then and I feel like giving up. I didn't get much training... about 3 weeks of training spread out over the last 6 months. I think I would be good at programming but this experience is kinda making me rethink my decision. I'm not sure if it's just me, or if this frustration is normal. How can I tell if programming is right for me?

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  • Where to start game programming for Android

    - by Marthin
    Hi, I'm new to game programming. But I'v got an ide for what I think would be a fun game for the Android platform. My question is, where do I start? Anyone got some good sites to recommend or perhaps a book or two. I'v got medium skills when it come to programming but i'v got a masters of science degree in computer engineering so i'm not totally unfamiliar with algorithms and stuff. Thx for any help! /Marthin

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  • Will Beej's Guide to Network programming point me the right way to be able to make multiplayer games and a web broswer?

    - by Logan545
    I'm new to socket programming in C, and I've found the Beej's Guide to Networking programming. It looks fine and all, however, I just wanted to ask whether this tutorial will point me in the right direction in terms of network programming. I plan to build a game in opengl that will be multiplayer using c+ and possibly a web browser. I know this tutorial would by no means teach me how to do this, but would this be a good way to start off on my path?

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  • buffer size for socket connection in c++

    - by wyatt
    I'm trying to build a basic POP3 mail client in C/++, but I've run into a bit of an issue. Since you have to define the buffer size when building the program, but a message can be arbitrarily large, how do you, say, get the mail server to send it to you in parts? And if this isn't the correct means of solving the problem, what is? And while I'm here, can anyone confirm for me that RFC 2822 is still the current document defining email layout? Thanks

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  • socket programming: How do I handle out of band data

    - by soulmerge
    I just looked into wikipedia's entry on out-of-band data and as far as I understand, OOB data is somehow flagged more important and treated as ordinary data, but transmitted in a seperate stream, which profoundly confuses me. The actual question would be (besides "Could someone explain what OOB data is?"): I'm writing a unix application that uses sockets and need to make use of select() and was wondering what to do with the exceptfds parameter? Do I need to put all my sockets into this parameter and react to such events? Or do I just ignore them?

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  • How to deal with MySQL Connector/ODBC error "Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock'"

    - by user12653020
    I am sure many users run into a mysterious problem when perfectly working ODBC configurations started failing with errors like: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' The above error message might be preceded with something like [nxDc[yQ]. At the same time odbc.ini specifies in its DSN different SOCKET=/tmp/mysql.sock or a TCP connection SERVER=<remote_host_or_ip>. The question is, what had happened that the ODBC driver started to ignore the DSN options? The clue lies in the corrupted string [nxDc[yQ], which actually was [UnixODBC][MySQL] with each 2nd symbol removed. This is the case of bad conversion from SQLCHAR to SQLWCHAR. The UnixODBC driver manager took a single-byte character string from the client application and tried to convert it into the wide (multi-byte) characters for the Unicode version of MyODBC driver: Initially the piece of the connection string was represented by 1-byte chars like: [S][E][R][V][E][R][=][m][y][h][o][s][t][;] after the bad conversion to wide chars (commonly 2-byte UTF-16) [SE][RV][ER][=m][yh][os][t;] instead of [S\0][E\0][R\0][V\0][E\0][R\0][=\0][m\0][y\0][h\0][o\0][s\0][t\0][;\0] Naturally, the MyODBC driver could not parse the bad string and tried to use the default connection type (SOCKET) with the default value (/var/lib/mysql/mysql.sock) Now we know what happened, but why it happened? In most cases it happened because of using ODBCManageDataSourcesQ4 utility or its older analog ODBCConfig. When registering ODBC drivers they put lots of additional options and one of these options badly affects the UnixODBC driver manager itself. The solution is simple - remove or comment out the option in odbcinst.ini file (it is empty by default) set for the driver: [MySQL ODBC 5.2.6 Driver] Description    = Driver         = /home/dbs/myodbc526/lib/libmyodbc5w.so Driver64       = /home/dbs/myodbc526/lib/libmyodbc5w.so Setup          = /home/dbs/myodbc526/lib/libmyodbc5S.so Setup64        = /home/dbs/myodbc526/lib/libmyodbc5S.so UsageCount     = 1 CPTimeout      = 0 CPTimeToLive   = 0 IconvEncoding  =  # <--------- remove this line Trace          = TraceFile      = TraceLibrary   = After applying this simple solution (remove the line with IconvEncoding = ) everything came to normal. Prior to removing that line I tried putting different encoding names there, but the result was not good, so I really don't know how to properly use it. Unfortunately, UnixODBC manuals say nothing about it. Therefore, removing this option was the only way to get things done.

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  • How do I transition from physics and math to programming?

    - by inovaovao
    I'm a physics PhD with little actual programming experience. I've always liked programming and played around with BASIC, Pascal as a teen, but the extent of my experience writing complex programs comes from an introductory course in computer science. Now I've decided that I'm more interested in programming than in physics and started to learn Java. Coming from a physics or math-heavy background, what would be the best strategy to maximize my value in the field?

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  • Alternative languages for embedded programming

    - by RHaguiuda
    I`m looking for alternatives programming languages (from assembly, C, C++ and basic) to embedded (microcontroller) programming. Is it possible for example, to programm microcontrollers in C# or Java? Maybe Ruby or Phyton? If possible, please post development tools and hardware used. Thanks

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  • breaking out from socket select

    - by kamziro
    I have a loop which basically calls this every few seconds (after the timeout): while(true){ if(finished) return; switch(select(FD_SETSIZE, &readfds, 0, 0, &tv)){ case SOCKET_ERROR : report bad stuff etc; return; default : break; } // do stuff with the incoming connection } So basically for every few seconds (which is specified by tv), it reactivates the listening. This is run on thread B (not a main thread). There are times when I want to end this acceptor loop immediately from thread A (main thread), but seems like I have to wait until the time interval finishes.. Is there a way to disrupt the select function from another thread so thread B can quit instantly?

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  • Terminate an inactive socket connection from TIdTCPServer

    - by A.J.
    We have an application which listens for incoming TCP requests using the Indy 10.1.1 components that ship with Delphi 2007. Occassionally we receive incoming connections which are not from our client application. Typically, one of two things happens: 1) the connection is terminated by the client before any data is received, or 2) data is received which we're not expecting and we manually terminate the connection. However, we've received connections where no data is received and appear to persist until the client terminates the connection from their end. Is there a way to terminate such a connection from the server if no data is received after a specified amount of time?

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  • How do I detect server status in a port scanner java implementation

    - by akz
    I am writing a port scanner in Java and I want to be able to distinct the following 4 use cases: port is open port is open and server banner was read port is closed server is not live I have the following code: InetAddress address = InetAddress.getByName("google.com"); int[] ports = new int[]{21, 22, 23, 80, 443}; for (int i = 0; i < ports.length; i++) { int port = ports[i]; Socket socket = null; try { socket = new Socket(address, port); socket.setSoTimeout(500); System.out.println("port " + port + " open"); BufferedReader reader = new BufferedReader( new InputStreamReader(socket.getInputStream())); String line = reader.readLine(); if (line != null) { System.out.println(line); } socket.close(); } catch (SocketTimeoutException ex) { // port was open but nothing was read from input stream ex.printStackTrace(); } catch (ConnectException ex) { // port is closed ex.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { if (socket != null && !socket.isClosed()) { try { socket.close(); } catch (Exception e) { e.printStackTrace(); } } } } The problem is that I get a ConnectionException both when the port is closed and the server cannot be reached but with a different exception message: java.net.ConnectException: Connection timed out: connect when the connection was never established and java.net.ConnectException: Connection refused: connect when the port was closed so I cannot make the distinction between the two use cases without digging into the actual exception message. Same thing happens when I try a different approach for the socket creation. If I use: socket = new Socket(); socket.setSoTimeout(500); socket.connect(new InetSocketAddress(address, port), 1000); I have the same problem but with the SocketTimeoutException instead. I get a java.net.SocketTimeoutException: Read timed out if port was open but there was no banner to be read and java.net.SocketTimeoutException: connect timed out if server is not live or port is closed. Any ideas? Thanks in advance!

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  • MapReduce programming system in java-actionscript

    - by eco_bach
    Just finished reading ch23 in the excellent 'Beautiful Code' http://oreilly.com/catalog/9780596510046 on Distributed Programming with MapReduce. I understand that MapReduce is a programming system designed for large-scale data processing problems, but I have a hard time getting my head around the basic examples given and how I might apply them in real world situations. Can someone give a simple example of MapReduce implemented using either java, javascript or actionscript?

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  • How to stay connected to the programming community?

    - by Anton
    I often find myself detached from the programming community and I generally find out about all the "cool" things that are happening after they have already happened. So my question is how do you stay connected and up to date with the programming community? Podcasts, blogs, meet ups, conventions, twitter, talking with your co-workers whatever it may be that keeps you connected. Please provide actual examples of which blogs, talks, etc you use.

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  • XML RPC client for C# over secured socket (https)

    - by Ummar
    I have a secured (https) XML-RPC server written in python, and I have tested it with a python based client. but I need a C# based client for it, I have given a try to xml-rpc.net but it is not working with https? can any one please help me out? or I will have to write a client from scratch? Thanks

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  • GUI programming, what to learn, already know console C++

    - by conqrr
    i have already learnt c++ console(love it!) and want to do gui programming, i have looked at Qt but i dont like the size of exe produced at all,even after compressing or static linking.... Shall i learn c# and gui programming?? is it easy to move from c++? what is dot net exactly by the way and how can it be useful to me and my CV in future??

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