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  • Flex, continuous scanning stream (from socket). Did I miss something using yywrap()?

    - by Diederich Kroeske
    Working on a socketbased scanner (continuous stream) using Flex for pattern recognition. Flex doesn't find a match that overlaps 'array bounderies'. So I implemented yywrap() to setup new array content as soon yylex() detects < (it will call yywrap). No success so far. Basically (for pin-pointing my problem) this is my code: %{ #include <stdio.h> #include <string.h> #include <stdlib.h> #define BUFFERSIZE 26 /* 0123456789012345678901234 */ char cbuf1[BUFFERSIZE] = "Hello everybody, lex is su"; // Warning, no '\0' char cbuf2[BUFFERSIZE] = "per cool. Thanks! "; char recvBuffer[BUFFERSIZE]; int packetCnt = 0; YY_BUFFER_STATE bufferState1, bufferState2; %} %option nounput %option noinput %% "super" { ECHO; } . { printf( "%c", yytext[0] );} %% int yywrap() { int retval = 1; printf(">> yywrap()\n"); if( packetCnt <= 0 ) // Stop after 2 { // Copy cbuf2 into recvBuffer memcpy(recvBuffer, cbuf2, BUFFERSIZE); // yyrestart(NULL); // ?? has no effect // Feed new data to flex bufferState2 = yy_scan_bytes(recvBuffer, BUFFERSIZE); // packetCnt++; // Tell flex to resume scanning retval = 0; } return(retval); } int main(void) { printf("Lenght: %d\n", (int)sizeof(recvBuffer)) ; // Copy cbuf1 into recvBuffer memcpy(recvBuffer, cbuf1, BUFFERSIZE); // packetCnt = 0; // bufferState1 = yy_scan_bytes(recvBuffer, BUFFERSIZE); // yylex(); yy_delete_buffer(bufferState1); yy_delete_buffer(bufferState2); return 0; } This is my output: dkmbpro:test dkroeske$ ./text Lenght: 26 Hello everybody, lex is su>> yywrap() per cool. Thanks! >> yywrap() So no match on 'super'. According to the doc the lexxer is not 'reset' between yywrap's. What do I miss? Thanks.

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  • Is it possible to creating a Service without starting it?

    - by ThaMe90
    Hello all, I wonder, is it possible to create a Service, set some data, and then start it? I haven't come across a thread specific to this problem, so I would like to know if it is possible (if it is known of course). My problem is that I have a Service which listens to a DatagramSocket, but the socket in question needs to be set after creation, but before the start of the Service. The setting of the socket happens through the use of a Broadcast (I broadcast 2 Strings which hold the IP-Address & Port and the BroadcastReceiver then constructs a socket for me). When the Service is started, a Thread will start to run and listen to the supposedly created socket. This, sadly, doesn't happen. The socket will remain null and I can't set it when the Thread is running (This is another issue I hope to tackle in the future, if anybody got any ideas about this, please notify me). So, is what I want possible, or should I come up with another construct for achieving this goal?

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  • Book with C programs that have real programming examples.

    - by Siamore
    This is my first question on Stack Overflow, I would like to know about any c programming books that have real programs to introduce real problems as opposed to standard books with examples aimed to teach the language it should be sort of like a challenge with solutions so that concepts like recursion can be used i know that i should find solutions to existing problems to learn the language but this is my first attempt and i find it hard to understand some simple problems so i was hoping for a book with solutions.

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  • Can two different UDP socket in a system bind same port?

    - by swift
    I have an application which uses UDP connection, now when i try to run the app more than once its throwing me an exception java.net.BindException: Address already in use: Cannot bind but in my another app, which uses tcp connection, i can open two instance of the same app and its working fine. why this error only with UDP connection?

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  • How to make socket.recv(500) not stop a while loop.

    - by ImTooStupidForThis
    I made an IRC bot which uses a while true loop to receive whatever is said. To receive I use recv(500), but that stops the loop if there isn't anything to receive, but i need the loop to continue even if there isn't anything to receive. I need a makeshift timer to continue running. Example code: /A lot of stuff/ timer=0 while 1: timer=timer+1 line=s.recv(500) #If there is nothing to receive, the loop and thus the timer stop. /A lot of stuff/ So either I need a way to stop it stopping the loop, or I need a better timer.

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  • Installation problem Ubuntu 12.04 Crashing hardware error

    - by user93640
    I am running on Ubuntu 8.04 for quite some time without many problems. About almost a year ago or so I have been trying to upgrade to 10.04 LTS, but without any success. Each time when trying to upgrade or even newly install the installation process crashed after about an hour or so (I forgot exactly how long). Now I wanted to try Ubuntu 12.04 (not even installing, but I only selected "Try Ubuntu without installing") and I got similar errors. I did not try to install it, because of earlier experience with 10.04 when after I also lost 8.04 and had to install from scratch again (after which it worked). I get the following screen (as I am not allowed to upload photos here the text): 26.767262] [Hardware Error]: CPU 0: Machine Check Exception: 0 Bank 5: b200001804000e0f 26.767279] [Hardware Error]: TSC 0 26.767287] [Hardware Error]: PROCESSOR 0:6f6 TIME 1349017924 SOCKET 0 APIC 0 microcode 44 26.767297] [Hardware Error]: Run the above through 'mcelog --ascii' 26.767307] [Hardware Error]: CPU 1: Machine Check Exception: 0 Bank 1: b200000000000175 26.767316] [Hardware Error]: TSC 0 26.767323] [Hardware Error]: PROCESSOR 0:6f6 TIME 1349017924 SOCKET 0 APIC 1 microcode 44 26.767331] [Hardware Error]: Run the above through 'mcelog --ascii' 26.767339] [Hardware Error]: CPU 1: Machine Check Exception: 0 Bank 5: b200003000000e0f 26.767348] [Hardware Error]: TSC 0 26.767354] [Hardware Error]: PROCESSOR 0:6f6 TIME 1349017924 SOCKET 0 APIC 1 microcode 44 26.767363] [Hardware Error]: Run the above through 'mcelog --ascii' 26.767371] [Hardware Error]: CPU 1: Machine Check Exception: 4 Bank 1: b200000000000175 26.767379] [Hardware Error]: TSC 1bf231e65f 26.767386] [Hardware Error]: PROCESSOR 0:6f6 TIME 1349017951 SOCKET 0 APIC 1 microcode 44 26.767395] [Hardware Error]: Run the above through 'mcelog --ascii' 26.767403] [Hardware Error]: CPU 1: Machine Check Exception: 4 Bank 5: b200003008000e0f 26.767413] [Hardware Error]: TSC 1bf231e65f 26.767421] [Hardware Error]: PROCESSOR 0:6f6 TIME 1349017951 SOCKET 0 APIC 1 microcode 44 26.767429] [Hardware Error]: Run the above through 'mcelog --ascii' 26.767437] [Hardware Error]: CPU 0: Machine Check Exception: 5 Bank 5: b200001806000e0f 26.767447] [Hardware Error]: RIP |INEXACT| 60:<00000000c1018b5c> {mwait_idle+0x7c/0x1d0} 26.767464] [Hardware Error]: TSC 1bf231e674 26.767471] [Hardware Error]: PROCESSOR 0:6f6 TIME 1349017951 SOCKET 0 APIC 0 microcode 44 26.767480] [Hardware Error]: Run the above through 'mcelog --ascii' 26.767487] [Hardware Error]: Machine check: Processor context corrupt 26.767495] Kernel panic - not syncing: Fatal Machine check 26.767505] Pid: 579, comm: debconf-communi Tainted: G M 3.2.0.29-generic-pae #46-Ubuntu 26.767515] Call Trace: 26.767525] [<c158f812>] ? printk+0x2d/0x2f 26.767534] [<c158f6e0>] panic+0x5c/0x161 26.767542] [<c10247ef>] mce_panic.part.14+0x13f/0x170 26.767551] [<c1024872>] mce_panic+0x52/0x90 26.767558] [<c1024a18>] mce_reign+0x168/0x170 26.767565] [<c1024bb5>] mce_end+0x105/0x110 26.767572] [<c10252db>] do_machine_check+0x32b/0x4f0 26.767581] [<c1024fb0>] ? mce_log+0x120/0x120 26.767590] [<c15a5e47>] error_code+0x67/0x6c 26.767602] panic occurred, switching back to text console 26.768498] Rebooting in 30 seconds.. For information, I have also tried earlier Arch Linux. I can install it, but when I try to install a window manager (LXDE) again I got similar errors. Fedora also crashes when installing and also Mandriva did not work for me. Therefore I think something deep in the machine might be wrong. But as stated above I can (clean) install 8.04 and also 9.10 can be installed without problems. Also updates for 8.04 can be installed. My machine is dual boot with XP next to it on a different partition. My HW: Memory : 2.0 GiB; Processor 0: Intel(R) Core(TM)2 CPU 6320 @ 1.86GHz; Processor 1: Intel(R) Core(TM)2 CPU 6320 @ 1.86GHz; How can I install Ubuntu 12.04? Last option would be to completely format my machine and install everything from scratch, but even I am not sure if that would solve it in the end. Can anybody help me out?

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  • What Counts for a DBA: Skill

    - by drsql
    “Practice makes perfect:” right? Well, not exactly. The reality of it all is that this saying is an untrustworthy aphorism. I discovered this in my “younger” days when I was a passionate tennis player, practicing and playing 20+ hours a week. No matter what my passion level was, without some serious coaching (and perhaps a change in dietary habits), my skill level was never going to rise to a level where I could make any money at the sport that involved something other than selling tennis balls at a sporting goods store. My game may have improved with all that practice but I had too many bad practices to overcome. Practice by itself merely reinforces what we know and what we can figure out naturally. The truth is actually closer to the expression used by Vince Lombardi: “Perfect practice makes perfect.” So how do you get to become skilled as a DBA if practice alone isn’t sufficient? Hit the Internet and start searching for SQL training and you can find 100 different sites. There are also hundreds of blogs, magazines, books, conferences both onsite and virtual. But then how do you know who is good? Unfortunately often the worst guide can be to find out the experience level of the writer. Some of the best DBAs are frighteningly young, and some got their start back when databases were stored on stacks of paper with little holes in it. As a programmer, is it really so hard to understand normalization? Set based theory? Query optimization? Indexing and performance tuning? The biggest barrier often is previous knowledge, particularly programming skills cultivated before you get started with SQL. In the world of technology, it is pretty rare that a fresh programmer will gravitate to database programming. Database programming is very unsexy work, because without a UI all you have are a bunch of text strings that you could never impress anyone with. Newbies spend most of their time building UIs or apps with procedural code in C# or VB scoring obvious interesting wins. Making matters worse is that SQL programming requires mastery of a much different toolset than most any mainstream programming skill. Instead of controlling everything yourself, most of the really difficult work is done by the internals of the engine (written by other non-relational programmers…we just can’t get away from them.) So is there a golden road to achieving a high skill level? Sadly, with tennis, I am pretty sure I’ll never discover it. However, with programming it seems to boil down to practice in applying the appropriate techniques for whatever type of programming you are doing. Can a C# programmer build a great database? As long as they don’t treat SQL like C#, absolutely. Same goes for a DBA writing C# code. None of this stuff is rocket science, as long as you learn to understand that different types of programming require different skill sets and you as a programmer must recognize the difference between one of the procedural languages and SQL and treat them differently. Skill comes from practicing doing things the right way and making “right” a habit.

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  • I've got two technical degrees but little in the way of experience. How do I get into programming? [closed]

    - by Neonfirelights
    I'm looking for a job, I want to break into programming. I'm looking for the right sort of role and the right place to look for it; I would really appreciate input from someone with industry experience. I've got an excellent academic record: BSc Physics (2:1), MSc Computer Graphics, Vision and Imaging (expecting Merit) from two world ranking universities. I have advanced technical knowledge of C/C++ and Matlab and experience working with C# and VB.NET. Unfortunately I don't have much in the way of commercial experience; unlike a lot of people I know my under-graduate didn't come with a sandwich placement. Where can I go to break into the software industry?

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  • Poco SocketReactors for a Proxy Server

    - by Genesis
    Can anyone give me some idea of the best way to implement a non-blocking proxy server using a Poco Socket Reactor? Currently I have a blocking implementation where if a readable notification arrives from the client I am writing what is read directly to the server, and if a readable notification arrives from the server I am writing what is read directly to the client. To achieve this I keep the thread that initiated the server connection alive but I would prefer to switch to non-blocking and have any threads which are used to initiate a connection removed once the server and client sockets are registered with the reactor and the SOCKS5 handshake is over. With a SocketReactor one can register event handlers for a single socket but the trouble is I would need to store whatever is read from that socket in a global buffer until the corresponding server socket is ready to be written to as from my testing I dont seem to be able to just write directly to the server when client data arrives. I am thinking of using a struct that contains the client socket, server socket, client buffer and server buffer and whenever a writable notification comes along for either the client or server, finding the corresponding buffer and writing this. Any thoughts?

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  • 500 error using lighttpd, fastcgi and PHP on file upload

    - by Dan
    I have a server running lighttpd with fastcgi, and it appears to be working correctly. However when I try to upload a file using a form, I get a 500 Internal server error, along with the following in the logs: 2012-03-23 18:25:09: (mod_fastcgi.c.2566) unexpected end-of-file (perhaps the fastcgi process died): pid: 2755 socket: unix:/tmp/php-fastcgi-1.socket-0 2012-03-23 18:25:09: (mod_fastcgi.c.3354) response not received, request sent: 50437 on socket: unix:/tmp/php-fastcgi-1.socket-0 for /index.php?url=brand/manager, closing connection I've been looking around for a long while now trying to find a solution to the issue, but nothing I'm trying is working. My current fastcgi conf looks as follows: server.modules += ( "mod_fastcgi" ) fastcgi.server = ( ".php" => (( "socket" => "/tmp/php-fastcgi-1.socket", "bin-path" => "/usr/bin/php-cgi", "allow-x-send-file" => "enable", "max-procs" => 1, "broken-scriptfilename" => "enable" )) ) If anyone could suggest if there is anything wrong in the configuration it would be greatly appreciated, or any suggestion as to what I might do? As I say, it is only happening when trying to upload a file (the file in question being only 45k). Thanks, Dan

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  • handling java exception

    - by Noona
    This questions is related to java exception, why are there some cases that when an exception thrown the program exits even though the exception was caught and there was no exit() statement? my code looks something like this void bindProxySocket(DefaultHttpClientConnection proxyConnection, String hostName, HttpParams params) { if (!proxyConnection.isOpen()) { Socket socket = null; try { socket = new Socket(hostName, 80); } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } try { proxyConnection.bind(socket, params); } catch(IOException e) { System.err.println ("couldn't bind socket"); e.printStackTrace(); } } } and then I call this method like this: bindProxySocket(proxyConn, hostName, params1); but, the program exits, although I want to handle the exception by doing something else, can it be because I didn't enclose the method call within a try catch clause? what happens if I catch the exception again even though it's already in the method? and what should I do if i want to clean resources only if an exception occurs and otherwise I want to continue with the program? I am guessing in this case I have to include the whole piece of code until I can clean the resources with in a try statement or can I do it in the handle exception statement? some of these questions are on this specific case, but I would like to get a thorough answer to all my questions for future reference. thanks

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  • Outgoing UDP sniffer in python?

    - by twneale
    I want to figure out whether my computer is somehow causing a UDP flood that is originating from my network. So that's my underlying problem, and what follows is simply my non-network-person attempt to hypothesize a solution using python. I'm extrapolating from recipe 13.1 ("Passing Messages with Socket Datagrams") from the python cookbook (also here). Would it possible/sensible/not insane to try somehow writing an outgoing UDP proxy in python, so that outgoing packets could be logged before being sent on their merry way? If so, how would one go about it? Based on my quick research, perhaps I could start a server process listening on suspect UDP ports and log anything that gets sent, then forward it on, such as: import socket s =socket.socket(socket.AF_INET, socket.SOCK_DGRAM) s.bind(("", MYPORT)) while True: packet = dict(zip('data', 'addr'), s.recvfrom(1,024)) log.info("Recieved {data} from {addr}.".format(**packet)) But what about doing this for a large number of ports simultaneously? Impractical? Are there drawbacks or other reasons not to bother with this? Is there a better way to solve this problem (please be gentle).

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  • EOFException in ObjectInputStream Only happens with Webstart not by java(w).exe ?!

    - by Houtman
    Hi, Anyone familiar with the differences in starting with Webstart(javaws.exe) compared to starting the app. using java.exe or javaw.exe regarding streams ? This is the exception which i ONLY get when using Webstart : java.io.EOFException at java.io.ObjectInputStream$PeekInputStream.readFully(Unknown Source) at java.io.ObjectInputStream$BlockDataInputStream.readShort(Unknown Source) at java.io.ObjectInputStream.readStreamHeader(Unknown Source) at java.io.ObjectInputStream.<init>(Unknown Source) at fasttools.jtools.dss.api.core.remoting.thinclient.RemoteSocketChannel.<init>(RemoteSocketChannel.java:77) This is how i setup the connections on both sides //==Server side== //Thread{ Socket mClientSocket = cServSock.accept(); new DssServant(mClientSocket).start(); //} DssServant(Socket socket) throws DssException { try { OutputStream mOutputStream = new BufferedOutputStream( socket.getOutputStream() ); cObjectOutputStream = new ObjectOutputStream(mOutputStream); cObjectOutputStream.flush(); //publish streamHeader InputStream mInputStream = new BufferedInputStream( socket.getInputStream() ); cObjectInputStream = new ObjectInputStream(mInputStream); .. } catch (IOException e) { .. } .. } //==Client side== public RemoteSocketChannel(String host, int port, IEventDispatcher eventSubscriptionHandler) throws DssException { cHost = host; port = (port == 0 ? DssServer.PORT : port); try { cSocket = new Socket(cHost, port); OutputStream mOutputStream = new BufferedOutputStream( cSocket.getOutputStream() ); cObjectOut = new ObjectOutputStream(mOutputStream); cObjectOut.flush(); //publish streamHeader InputStream mInputStream = new BufferedInputStream( cSocket.getInputStream() ); cObjectIn = new ObjectInputStream(mInputStream); } catch (IOException e) { .. } .. } Thanks [EDIT] Webstart console says: Java Web Start 1.6.0_19 Using JRE version 1.6.0_19-b04 Java HotSpot(TM) Client VM Server is running same 1.6u19

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  • What can cause a spontaneous EPIPE error without either end calling close() or crashing?

    - by Hongli
    I have an application that consists of two processes (let's call them A and B), connected to each other through Unix domain sockets. Most of the time it works fine, but some users report the following behavior: A sends a request to B. This works. A now starts reading the reply from B. B sends a reply to A. The corresponding write() call returns an EPIPE error, and as a result B close() the socket. However, A did not close() the socket, nor did it crash. A's read() call returns 0, indicating end-of-file. A thinks that B prematurely closed the connection. Users have also reported variations of this behavior, e.g.: A sends a request to B. This works partially, but before the entire request is sent A's write() call returns EPIPE, and as a result A close() the socket. However B did not close() the socket, nor did it crash. B reads a partial request and then suddenly gets an EOF. The problem is I cannot reproduce this behavior locally at all. I've tried OS X and Linux. The users are on a variety of systems, mostly OS X and Linux. Things that I've already tried and considered: Double close() bugs (close() is called twice on the same file descriptor): probably not as that would result in EBADF errors, but I haven't seen them. Increasing the maximum file descriptor limit. One user reported that this worked for him, the rest reported that it did not. What else can possibly cause behavior like this? I know for certain that neither A nor B close() the socket prematurely, and I know for certain that neither of them have crashed because both A and B were able to report the error. It is as if the kernel suddenly decided to pull the plug from the socket for some reason.

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