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  • What to Learn after C++?

    - by Stephen Whitmore
    I have been learning C++ for a while now, I find it very powerful. But, the problem is the the level of abstraction is not much and I have to do memory management myself. What are the languages that I can use which uses a higher level of abstraction.

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  • How can I manually uninstall .NET Framework Beta 2?

    - by DannyAsher
    Uninstalled VS2010 Beta 2. Uninstalled .NET Framework 4 Extended Beta 2. On attempting to uninstall .NET Framework 4 Client Profile Beta 2. I get Blocking Issues: You must uninstall the .NET Framework 4 Extended Beta 2 before you uninstall the .NET Framework 4 Client Profile Beta 2. On attempting to reinstall Framework 4 Beta 2 I get: Details: Same or higher version of .NET Framework 4 Beta 2 has already been installed on this computer. Please help! Can I simply remove registry entries and the C:\WINDOWS\Microsoft.NET\Framework\v4.0.21006 directory?

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  • Udp server sending only 0 bytes of data

    - by mawia
    Hi all, This is a simple Udp server.I am trying to transmit data to some clients,but unfortunetly it is unable to transmit data.Though send is running quite successfully but it is returning with a return value meaning it has send nothing.On the client they are receiving but again obviously,zero bytes. void* UdpServerStreamToClients(void *fileToServe) { int sockfd,n=0,k; struct sockaddr_in servaddr,cliaddr; socklen_t len; char dataToSend[1000]; sockfd=socket(AF_INET,SOCK_DGRAM,0); bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_addr.s_addr=htonl(INADDR_ANY); servaddr.sin_port=htons(32000); bind(sockfd,(struct sockaddr *)&servaddr,sizeof(servaddr)); FILE *fp; if((fp=fopen((char*)fileToServe,"r"))==NULL) { printf("can not open file "); perror("fopen"); exit(1); } int dataRead=1; while(dataRead) { len = sizeof(cliaddr); if((dataRead=fread(dataToSend,1,500,fp))<0) { perror("fread"); exit(1); } //sleep(2); for(list<clientInfo>::iterator it=clients.begin();it!=clients.end();it++) { cliaddr.sin_family = AF_INET; inet_aton(inet_ntoa(it->addr.sin_addr),&cliaddr.sin_addr); cliaddr.sin_port = htons(it->udp_port); n=sendto(sockfd,dataToSend,sizeof(dataToSend),0,(struct sockaddr *)&cliaddr,len); cout<<"number of bytes send by udp: "<< n << endl; printf("SEND this message %d : %s to %s :%d \n",n,dataToSend,inet_ntoa(cliaddr.sin_addr), ntohs(cliaddr.sin_port)); } } } I am checking the value of sizeof(dataTosend) and it is pretty much as expected ie thousand ie the size of buffer. Are you people seeing some possible flaw in it. All of the help in this regard will be appreciated. Thanks!

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  • List filtering: list comprehension vs. lambda + filter

    - by Agos
    I happened to find myself having a basic filtering need: I have a list and I have to filter it by an attribute of the items. My code looked like this: list = [i for i in list if i.attribute == value] But then i thought, wouldn't it be better to write it like this? filter(lambda x: x.attribute == value, list) It's more readable, and if needed for performance the lambda could be taken out to gain something. Question is: are there any caveats in using the second way? Any performance difference? Am I missing the Pythonic Way™ entirely and should do it in yet another way (such as using itemgetter instead of the lambda)? Thanks in advance

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  • an error "variable of field declared void"

    - by lego69
    I have this code: header - test.h Inside header I have some class Z and definitions of two functions test and test2 I call function test2 from test void test2(Z z, Z const *za); this is implementation of the function: void test2(Z z, Z const *za){ int i = z; //this row works cout << i << endl; } I call it from test: test2(z1, za1); // za1 is pinter to object and z1 is some object but in my header I receive an 3 errors: Multiple markers at this line - initializer expression list treated as compound expression - `A' was not declared in this scope - variable or field `quiz2' declared void can somebody please explain why? thanks in advance

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  • Binding on a port with netpipes/netcat

    - by mindas
    I am trying to write a simple bash script that is listening on a port and responding with a trivial HTTP response. My specific issue is that I am not sure if the port is available and in case of bind failure I fall back to next port until bind succeeds. So far to me the easiest way to achieve this was something like: for (( i=$PORT_BASE; i < $(($PORT_BASE+$PORT_RANGE)); i++ )) do if [ $DEBUG -eq 1 ] ; then echo trying to bind on $i fi /usr/bin/faucet $i --out --daemon echo test 2>/dev/null if [ $? -eq 0 ] ; then #success? port=$i if [ $DEBUG -eq 1 ] ; then echo "bound on port $port" fi break fi done Here I am using faucet from netpipes Ubuntu package. The problem with this is that if I simply print "test" to the output, curl complains about non-standard HTTP response (error code 18). That's fair enough as I don't print HTTP-compatible response. If I replace echo test with echo -ne "HTTP/1.0 200 OK\r\n\r\ntest", curl still complains: user@server:$ faucet 10020 --out --daemon echo -ne "HTTP/1.0 200 OK\r\n\r\ntest" ... user@client:$ curl ip.of.the.server:10020 curl: (56) Failure when receiving data from the peer I think the problem lies in how faucet is printing the response and handling the connection. For example if I do the server side in netcat, curl works fine: user@server:$ echo -ne "HTTP/1.0 200 OK\r\n\r\ntest\r\n" | nc -l 10020 ... user@client:$ curl ip.of.the.server:10020 test user@client:$ I would be more than happy to replace faucet with netcat in my main script, but the problem is that I want to spawn independent server process to be able to run client from the same base shell. faucet has a very handy --daemon parameter as it forks to background and I can use $? (exit status code) to check if bind succeeded. If I was to use netcat for a similar purpose, I would have to fork it using & and $? would not work. Does anybody know why faucet isn't responding correctly in this particular case and/or can suggest a solution to this problem. I am not married neither to faucet nor netcat but would like the solution to be implemented using bash or it's utilities (as opposed to write something in yet another scripting language, such as Perl or Python).

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  • True / false evaluation doesn't work as expected in Scheme

    - by ron
    I'm trying to compare two booleans : (if (equal? #f (string->number "123b")) "not a number" "indeed a number") When I run this in the command line of DrRacket I get "not a number" , however , when I put that piece of code in my larger code , the function doesn't return that string ("not a number") , here's the code : (define (testing x y z) (define badInput "ERROR") (if (equal? #f (string->number "123b")) "not a number" "indeed a number") (display x)) And from command line : (testing "123" 1 2) displays : 123 Why ? Furthermore , how can I return a value , whenever I choose ? Here is my "real" problem : I want to do some input check to the input of the user , but the thing is , that I want to return the error message if I need , before the code is executed , because if won't - then I would run the algorithm of my code for some incorrect input : (define (convert originalNumber s_oldBase s_newBase) (define badInput "ERROR") ; Input check - if one of the inputs is not a number then return ERROR (if (equal? #f (string->number originalNumber)) badInput) (if (equal? #f (string->number s_oldBase)) badInput) (if (equal? #f (string->number s_newBase)) badInput) (define oldBase (string->number s_oldBase)) (define newBase (string->number s_newBase)) (define outDecimal (convertIntoDecimal originalNumber oldBase)) (define result "") ; holds the new number (define remainder 0) ; remainder for each iteration (define whole 0) ; the whole number after dividing (define temp 0) (do() ((= outDecimal 0)) ; stop when the decimal value reaches 0 (set! whole (quotient outDecimal newBase)) ; calc the whole number (set! temp (* whole newBase)) (set! remainder (- outDecimal temp)) ; calc the remainder (set! result (appending result remainder)) ; append the result (set! outDecimal (+ whole 0)) ; set outDecimal = whole ) ; end of do (if (> 1 0) (string->number (list->string(reverse (string->list result))))) ) ;end of method This code won't work since it uses another method that I didn't attach to the post (but it's irrelevant to the problem . Please take a look at those three IF-s ... I want to return "ERROR" if the user put some incorrect value , for example (convert "23asb4" "b5" "9") Thanks

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  • Client/Server communication via internet

    - by user957829
    Hi, Which is the best solution to communicate bidirectionally between a remote server and a client behind an internet box? UPnP with Sockets. HTTPS/Database Server and the client make 1 request every Xsec to know if there is new data. Client opens 1 connection on the server and it maintains open to make a tunnel. Thanks in advance for your help

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  • Is there any reason for a blocking call to winsock send() function on Vista to return immediately ?

    - by ivymike
    Hi All, Is there any reason for a blocking call to winsock's send() function on Vista to return immediately ? It works with expected delay on XP and below. I'm wondering if this has got anything to do with auto-tuning feature of Vista. Code: char *pBuffer; // pointer to data int bytes; // total size int i = 0, j=0; while (i < bytes) { j = send(m_sock, pBuffer+i, bytes-i, 0); i+=j; } Thanks, Pavan

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  • Detecting the Loopback Adapter

    - by BlueSkies
    What is the best way for detecting whether a network interface is a loopback adapter? The windows API's GetAdaptersInfo and GetAdaptersAddresses state in the documentation that they will return whether an interface is a loopback through the Type (MIB_IF_TYPE_LOOPBACK) but neither of these do for the Microsoft Loopback Adapter at least, it is reported as a standard ethernet interface. I could try checking for the default MAC of the Loopback adapter but this can be easily spoofed. I could check for the name "Microsoft Loopback Adapter" in the description but this may have translation issues and may lead to other issues. IP addresses can also be changed. What is the most robust method for doing this?

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  • Listening UDP or switch to TCP in a MFC application

    - by Alexander.S
    I'm editing a legacy MFC application, and I have to add some basic network functionalities. The operating side has to receive a simple instruction (numbers 1,2,3,4...) and do something based on that. The clients wants the latency to be as fast as possible, so naturally I decided to use datagrams (UDP). But reading all sorts of resources left me bugged. I cannot listen to UDP sockets (CAsyncSocket) in MFC, it's only possible to call Receive which blocks and waits. Blocking the UI isn't really a smart. So I guess I could use some threading technique, but since I'm not all that experienced with MFC how should that be implemented? The other part of the question is should I do this, or revert to TCP, considering reliability and implementation issues. I know that UDP is unreliable, but just how unreliable is it really? I read that it is up to 50% faster, which is a lot for me. References I used: http://msdn.microsoft.com/en-us/library/09dd1ycd(v=vs.80).aspx

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  • How to filter and intercept Linux packets by using net_dev_add() API?

    - by Khajavi
    I'm writing ethernet network driver for linux. I want to receive packets, edit and resend them. I know how to edit the packet in packet_interceptor function, but how can I drop incoming packets in this function?? #include <linux/netdevice.h> #include <linux/skbuff.h> #include <linux/ip.h> #include <net/sock.h> struct packet_type my_proto; int packet_interceptor(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) { // I dont want certain packets go to upper in net_devices for further processing. // How can I drop sk_buff here?! return 0; } static int hello_init( void ) { printk(KERN_INFO "Hello, world!\n"); my_proto.type = htons(ETH_P_ALL); my_proto.dev = NULL; my_proto.func = packet_interceptor; dev_add_pack(&my_proto); return 0; } static void hello_exit(void) { dev_remove_pack(&my_proto); printk(KERN_INFO "Bye, world\n"); } module_init(hello_init); module_exit(hello_exit);

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  • Linux Kernel - Integer to ASCII

    - by DRX-Z
    I need to convert an integer to it's ASCII representation from within the Linux Kernel. How can I do this? I can't find any built-in conversion methods. Are there any already in the kernel or do I need to add my own?

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  • Easy way to convert c code to assembly?

    - by Bob
    Is there an easy way (like a free program) that can covert c/c++ code to x86 assembly? I know that any c compiler does something very similar and that I can just compile the c code and then disassemble the complied executable, but that's kind of an overkill, all I want is to convert a few lines of code. Does anyone know of some program that can do that?

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  • Choosing a Job based on languages?

    - by Alan
    How often is language the deciding factor for selecting a job? Many of us here are well versed in many languages, C++, Java, C#, and likely have many other languages under our belt for the right occassion (really any occasion is the right occasion for Python, AMIRITE?), so this isn't so much a question of choosing a job that is a good fit based on your skill set. Rather, if you are skilled with most languages, do you pick your favorite, or do you follow the money (given the tight economy). I'm considering coming out of retirement, and have started to look around and what's available. Over the years, I've moved towards C# and Python; many jobs in the area are looking for .NET developers, but there are plenty of them that do not. I cut my teef on C++, consider myself adept at the language, and know my way around a Java. But I find myself really digging what they're doing to C#, and I have always loved python. So when I see an interesting job req that is looking for C++ developers; it gives me 2nd thoughts. Not because I can't cut it, but because I don't know if I want to go back to C++. Even if the work will be interesting, how important is the language to you?

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  • Trying to packetize TCP with non-blocking IO is hard! Am I doing something wrong?

    - by Ricket
    Oh how I wish TCP was packet-based like UDP is! But alas, that's not the case, so I'm trying to implement my own packet layer. Here's the chain of events so far (ignoring writing packets) Oh, and my Packets are very simply structured: two unsigned bytes for length, and then byte[length] data. (I can't imagine if they were any more complex, I'd be up to my ears in if statements!) Server is in an infinite loop, accepting connections and adding them to a list of Connections. PacketGatherer (another thread) uses a Selector to figure out which Connection.SocketChannels are ready for reading. It loops over the results and tells each Connection to read(). Each Connection has a partial IncomingPacket and a list of Packets which have been fully read and are waiting to be processed. On read(): Tell the partial IncomingPacket to read more data. (IncomingPacket.readData below) If it's done reading (IncomingPacket.complete()), make a Packet from it and stick the Packet into the list waiting to be processed and then replace it with a new IncomingPacket. There are a couple problems with this. First, only one packet is being read at a time. If the IncomingPacket needs only one more byte, then only one byte is read this pass. This can of course be fixed with a loop but it starts to get sorta complicated and I wonder if there is a better overall way. Second, the logic in IncomingPacket is a little bit crazy, to be able to read the two bytes for the length and then read the actual data. Here is the code, boiled down for quick & easy reading: int readBytes; // number of total bytes read so far byte length1, length2; // each byte in an unsigned short int (see getLength()) public int getLength() { // will be inaccurate if readBytes < 2 return (int)(length1 << 8 | length2); } public void readData(SocketChannel c) { if (readBytes < 2) { // we don't yet know the length of the actual data ByteBuffer lengthBuffer = ByteBuffer.allocate(2 - readBytes); numBytesRead = c.read(lengthBuffer); if(readBytes == 0) { if(numBytesRead >= 1) length1 = lengthBuffer.get(); if(numBytesRead == 2) length2 = lengthBuffer.get(); } else if(readBytes == 1) { if(numBytesRead == 1) length2 = lengthBuffer.get(); } readBytes += numBytesRead; } if(readBytes >= 2) { // then we know we have the entire length variable // lazily-instantiate data buffers based on getLength() // read into data buffers, increment readBytes // (does not read more than the amount of this packet, so it does not // need to handle overflow into the next packet's data) } } public boolean complete() { return (readBytes > 2 && readBytes == getLength()+2); } Basically I need feedback on my code. Please suggest any improvements. Even overhauling my entire system would be okay, if you have suggestions for how better to implement the whole thing. Book recommendations are welcome too; I love books. I just get the feeling that something isn't quite right.

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  • Is this multi line if statement too complex?

    - by AndHeCodedIt
    I am validating input on a form and attempting to prompt the user of improper input(s) based on the combination of controls used. For example, I have 2 combo boxes and 3 text boxes. The 2 combo boxes must always have a value other than the first (default) value, but one of three, or two of three, or all text boxes can be filled to make the form valid. In one such scenario I have a 6 line if statement to try to make the test easily readable: if ((!String.Equals(ComboBoxA.SelectedValue.ToString(), DEFAULT_COMBO_A_CHOICE.ToString()) && !String.IsNullOrEmpty(TextBoxA.Text) && !String.Equals(ComboBoxB.SelectedValue.ToString(), DEFAULT_COMBO_B_CHOICE.ToString())) || (!String.IsNullOrEmpty(TextBoxB.Text) || !String.IsNullOrEmpty(TextBoxC.Text))) { //Do Some Validation } I have 2 questions: Should this type of if statement be avoided at all cost? Would it be better to enclose this test in another method? (This would be a good choice as this validation will happen in more than one scenario) Thanks for your input(s)!

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