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  • "...redeclared as different kind of symbol"?

    - by CodeNewb
    #include <stdio.h> #include <math.h> double integrateF(double low, double high) { double low = 0; double high = 20; double delta_x=0; double x, ans; double s = 1/2*exp((-x*x)/2); for(x=low;x<=high;x++) delta_x = x+delta_x; ans = delta_x*s; return ans; } It says that low and high are "redeclared as different type of symbol" and I don't know what that means. Basically, all I'm doing here (READ: trying) is integrating from low (which I set to 0) to high (20) to find the Riemann sum. The for loop looks kinda trippy too...I'm so lost.

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  • How to compare string with const char*?

    - by arzeth
    #include <stdlib.h> #include <stdio.h> #include <iostream> #include <string.h> using namespace std; int main() { string cmd; while(strcmp(cmd.c_str(),"exit")==0 && strcmp(cmd.c_str(),"\exit")==0) { cin>>cmd; cout<<cmd; } return 0; } I am stuck.

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  • Reading line by line from a file in C

    - by mh234
    What I am trying to do is print out the contents of a file line by line. I run the program in terminal by doing: ./test testText.txt. When I do this, random characters are printed out but not what is in the file. The text file is located in the same folder as the makefile. What's wrong? #include <stdio.h> FILE *fp; int main(int argc, char *argv[]) { char line[15]; fp = fopen(*argv, "r"); while((fgets(line, 15, fp)) != NULL) { printf(line); printf("\n"); } }

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  • Compare to a defined constants in C?

    - by J.W.
    I am trying to compare to a defined constants in C, and I have simplified my program to the following.. #include "stdio.h" #include "stdlib.h" #define INVALID_VALUE -999; int main(int argc, const char* argv[]) { int test=0; if(test==INVALID_VALUE) //The error line.. return INVALID_VALUE; return 0; }; And when I use gcc to compile. it gives out error "error: expected ‘)’ before ‘;’ token" Any reason that this cannot be done.

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  • Unexpected output on initializing array by using both `element-by-element` & `designated` technique

    - by haccks
    C99 provides a feature to initialize arrays by using both element-by-element & designated method together as: int a[] = {2,1,[3] = 5,[5] = 9,6,[8] = 4}; On running the code: #include <stdio.h> int main() { int a[] = {2,1,[3] = 5,[0] = 9,4,[6] = 25}; for(int i = 0; i < sizeof(a)/sizeof(a[0]); i++) printf("%d ",a[i]); return 0; } (Note that Element 0 is initialized to 2 and then again initialised by designator [0] to 9) I was expecting that element 0(which is 2) will be replaced by 9(as designator [0] = 9) and hence o/p will become 9 1 0 5 4 0 25 Unfortunately I was wrong as o/p came; 9 4 0 5 0 0 25 Any explanation for unexpected o/p?

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  • sorting set of five string in alphabetical oder throwing warning?

    - by rost rost
    sorting set of five string in alphabetical oder throwing warning ?my code is below please help me to fix it #include<stdio.h> #include<string.h> int main() { char a[5][20],t[20]; int i,j; printf("enter 5 string\n") scanf("%s",a); for(i=1;i<5;i++) { for(j=1;j<5;j++) { if(strcmp(a[j-1],a[j])>0) { strcpy (t,a[j-1]); strcpy (a[j-1],a[j]); strcpy(a[j],t); } } } for(i=1;i<5;i++) printf("%s\n",a[i]); } ~

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  • Is this syntactically correct?

    - by Borrito
    I have code in one of the source file as follows: #include <stdio.h> #include <math.h> int a ; int b = 256 ; int c = 16 ; int d = 4 ; int main() { if ((d <= (b) && (d == ( c / sizeof(a)))) { printf("%d",sizeof(a) ); } return 0; } I have removed the casts and have simplified on the data names. The sizeof(a) can be taken as 4. I want to know if the the if syntax is a valid one and if so why doesn't it execute? PS : I haven't sat down on this for long due to time constraints. Pardon me if you find a childish error in the code.

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  • Inconsistent behaviour from SDL_BlitSurface

    - by bardes
    Here is an example code: #include <SDL/SDL.h> #include <SDL/SDL_image.h> #include <stdio.h> int main() { if(SDL_Init(SDL_INIT_EVERYTHING) == -1) { printf("SDL ERROR: %s", SDL_GetError()); return 1; } SDL_Surface *screen; screen = SDL_SetVideoMode(128, 128, 32, SDL_SWSURFACE); SDL_Surface *img; img = IMG_Load("./debug.png"); SDL_BlitSurface(img, NULL, screen, NULL); SDL_Flip(screen); SDL_Delay(1000); SDL_FreeSurface(img); SDL_Quit(); return 0; } It compiles fine, but when I run it sometimes it works and most times only part of the image is displayed. I really can't imagine what's causing that... EDIT: This is the image I'm using to test the program: http://img140.imageshack.us/img140/3858/debugi.png

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  • I have a Segmentation fault (core dumped) when using strcpy, malloc, and struct

    - by malsh002
    Okay, when I run this code, I have a segmentation fault #include<stdio.h> #include<stdlib.h> #include<string.h> #define MAX 64 struct example { char *name; }; int main() { struct example *s = malloc (MAX); strcpy(s->name ,"Hello World!!"); return !printf("%s\n", s->name); } the terminal output: alshamlan@alshamlan-VGN-CR520E:/tmp/interview$ make q1 cc -Wall -g q1.c -o q1 alshamlan@alshamlan-VGN-CR520E:/tmp/interview$ ./q1 Segmentation fault (core dumped) alshamlan@alshamlan-VGN-CR520E:/tmp/interview$ gedit q1.c Can someone explain what's going on? thanks.

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  • gcc segmentation fault on Ubuntu 12.04

    - by Yuval F
    I am trying to compile a C program on Ubuntu precise 12.04. Here's the program: #include <stdio.h> int main(int argc, char** argv) { printf("Hello World!"); return 0; } My gcc version is 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5). Initially it did not find cc1 so I added a soft link. Now I get this message when I try to compile: gcc: internal compiler error: Segmentation fault (program cc1) Compiling the same program with g++ works fine. I tried reinstalling build-essential, but to no avail. What am I missing? EDIT: I tried reinstalling according to @gertyvdijk's suggestion. As it did not help, here is the output of apt-cache policy gcc-4.6: gcc-4.6: Installed: 4.6.3-1ubuntu5 Candidate: 4.6.3-1ubuntu5 Version table: *** 4.6.3-1ubuntu5 0 500 http://il.archive.ubuntu.com/ubuntu/ precise/main amd64 Packages 100 /var/lib/dpkg/status and the output of ls -l /usr/bin/gcc: lrwxrwxrwx 1 root root 7 Mar 13 2012 /usr/bin/gcc -> gcc-4.6 EDIT #2: here's a verbose compiler output: gcc -v aaa.c Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.6/lto-wrapper Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.6.3-1ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.6 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu Thread model: posix gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) COLLECT_GCC_OPTIONS='-v' '-mtune=generic' '-march=x86-64' /usr/lib/gcc/x86_64-linux-gnu/4.6/cc1 -quiet -v -imultilib . -imultiarch x86_64-linux-gnu aaa.c -quiet -dumpbase aaa.c -mtune=generic -march=x86-64 -auxbase aaa -version -fstack-protector -o /tmp/ccHfcXMs.s gcc: internal compiler error: Segmentation fault (program cc1) Please submit a full bug report, with preprocessed source if appropriate. See <file:///usr/share/doc/gcc-4.6/README.Bugs> for instructions.

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  • Image loaded from TGA texture isn't displayed correctly

    - by Ramy Al Zuhouri
    I have a TGA texture containing this image: The texture is 256x256. So I'm trying to load it and map it to a cube: #import <OpenGL/OpenGL.h> #import <GLUT/GLUT.h> #import <stdlib.h> #import <stdio.h> #import <assert.h> GLuint width=640, height=480; GLuint texture; const char* const filename= "/Users/ramy/Documents/C/OpenGL/Test/Test/texture.tga"; void init() { // Initialization glEnable(GL_DEPTH_TEST); glViewport(-500, -500, 1000, 1000); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(45, width/(float)height, 1, 1000); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); gluLookAt(0, 0, -100, 0, 0, 0, 0, 1, 0); // Texture char bitmap[256][256][3]; FILE* fp=fopen(filename, "r"); assert(fp); assert(fread(bitmap, 3*sizeof(char), 256*256, fp) == 256*256); fclose(fp); glGenTextures(1, &texture); glBindTexture(GL_TEXTURE_2D, texture); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 256, 256, 0, GL_RGB, GL_UNSIGNED_BYTE, bitmap); } void display() { glClearColor(0, 0, 0, 0); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, texture); glColor3ub(255, 255, 255); glBegin(GL_QUADS); glVertex3f(0, 0, 0); glTexCoord2f(0.0, 0.0); glVertex3f(40, 0, 0); glTexCoord2f(0.0, 1.0); glVertex3f(40, 40, 0); glTexCoord2f(1.0, 1.0); glVertex3f(0, 40, 0); glTexCoord2f(1.0, 0.0); glEnd(); glDisable(GL_TEXTURE_2D); glutSwapBuffers(); } int main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE); glutInitWindowPosition(100, 100); glutInitWindowSize(width, height); glutCreateWindow(argv[0]); glutDisplayFunc(display); init(); glutMainLoop(); return 0; } But this is what I get when the window loads: So just half of the image is correctly displayed, and also with different colors.Then if I resize the window I get this: Magically the image seems to fix itself, even if the colors are wrong.Why?

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  • Why do "Joke" programming languages exist? [closed]

    - by ThePlan
    First of all please be aware this post contains some abusive language but I hope it will not bother anyone. I apologize for the bad language but that's what the name is. As I've been doing documentation on existing programming languages attempting to make a complete list of them I stumbled across terrible programming languages, which were clearly not made for actual use and implementation due to their insane difficulty. Languages such as Brainfu*k and LOLCODE or Whitespace are fool languages because they have no real use. For example, a "Hello world" program written in BrainFu*k. Taken from Wikipedia: The following program prints "Hello World!" and a newline to the screen: +++++ +++++ initialize counter (cell #0) to 10 [ use loop to set the next four cells to 70/100/30/10 > +++++ ++ add 7 to cell #1 > +++++ +++++ add 10 to cell #2 > +++ add 3 to cell #3 > + add 1 to cell #4 <<<< - decrement counter (cell #0) ] > ++ . print 'H' > + . print 'e' +++++ ++ . print 'l' . print 'l' +++ . print 'o' > ++ . print ' ' << +++++ +++++ +++++ . print 'W' > . print 'o' +++ . print 'r' ----- - . print 'l' ----- --- . print 'd' > + . print '!' > . print '\n' or another example taken from LOLCODE language: HAI CAN HAS STDIO? PLZ OPEN FILE "LOLCATS.TXT"? AWSUM THX VISIBLE FILE O NOES INVISIBLE "ERROR!" KTHXBYE These languages are very difficult to learn/read/work with. My question is - Why do they exist? What is the purpose of them? Also, is there an official "name" for these type of languages?

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  • Can I get a C++ Compiler to instantiate objects at compile time

    - by gam3
    I am writing some code that has a very large number of reasonably simple objects and I would like them the be created at compile time. I would think that a compiler would be able to do this, but I have not been able to figure out how. In C I could do the the following: #include <stdio.h> typedef struct data_s { int a; int b; char *c; } info; info list[] = { 1, 2, "a", 3, 4, "b", }; main() { int i; for (i = 0; i < sizeof(list)/sizeof(*list); i++) { printf("%d %s\n", i, list[i].c); } } Using #C++* each object has it constructor called rather than just being layed out in memory. #include <iostream> using std::cout; using std::endl; class Info { const int a; const int b; const char *c; public: Info(const int, const int, const char *); const int get_a() { return a; }; const int get_b() { return b; }; const char *get_c() const { return c; }; }; Info::Info(const int a, const int b, const char *c) : a(a), b(b), c(c) {}; Info list[] = { Info(1, 2, "a"), Info(3, 4, "b"), }; main() { for (int i = 0; i < sizeof(list)/sizeof(*list); i++) { cout << i << " " << list[i].get_c() << endl; } } I just don't see what information is not available for the compiler to completely instantiate these objects at compile time, so I assume I am missing something.

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  • I was stuck in implementing Simple Ftp with Winsock [migrated]

    - by user67449
    I want to implement a SimpleFtp with Winsock. But I was stuck in the maybe the file stream reading and writing. This is the Server. #include <WinSock2.h> #include <memory.h> #include <stdio.h> #include <iostream> using namespace std; #pragma comment(lib, "ws2_32.lib") #define MAX_FILE_NAME 100 #define DATA_PACK_SIZE 80*1000 // ??DataPack?????80KB #define SOCKKET_BUFFER_SIZE 80*1000 // socket??? #define FILE_BUFFER_SIZE DATA_PACK_SIZE-MAX_FILE_NAME-4*sizeof(int)-sizeof(u_long) //?????,??,??????content????? #define CONTENT_SIZE FILE_BUFFER_SIZE // DataPack?????content??? // Define a structure to hold the content of a file typedef struct FilePack{ char fName[MAX_FILE_NAME]; // File's name int fLen; // File's length int packNum; // Number of the DataPack int packLen; // DataPack's length int packCount; int contenLen; // the content length the DataPack actually holds u_long index; // ?????????? char content[CONTENT_SIZE]; // DataPack?????? }DataPack, *pDataPack; void WinsockInitial(){ WSADATA wsaData; WORD wVersionRequested; int err; wVersionRequested=MAKEWORD(2,2); err=WSAStartup(wVersionRequested, &wsaData); if(err!=0){ cout<<"Error at WSAStartup()."<<endl; exit(0); } if( LOBYTE(wsaData.wVersion)!=2 || HIBYTE(wsaData.wVersion)!=2 ){ cout<<"Error at version of Winsock. "<<endl; WSACleanup(); exit(0); } } void SockBind(SOCKET sock, int port, sockaddr_in &addrsock){ addrsock.sin_family=AF_INET; addrsock.sin_port=htons(port); addrsock.sin_addr.S_un.S_addr=htonl(INADDR_ANY); if( bind(sock, (sockaddr*)&addrsock, sizeof(addrsock)) == SOCKET_ERROR ){ cout<<"Error at bind(). Error: "<<GetLastError()<<endl; closesocket(sock); WSACleanup(); exit(0); } } void SockListen(SOCKET sock, int bak){ int err=listen(sock, bak); if(err==SOCKET_ERROR){ cout<<"Error at listen()."<<WSAGetLastError()<<endl; closesocket(sock); WSACleanup(); exit(0); } } int SockSend(DataPack &dataPack, SOCKET sock, char *sockBuf){ int bytesLeft=0, bytesSend=0; int idx=0; bytesLeft=sizeof(dataPack); // ?DataPack?????sockBuf??? memcpy(sockBuf, &dataPack, sizeof(dataPack)); while(bytesLeft>0){ bytesSend=send(sock, &sockBuf[idx], bytesLeft, 0); if(bytesSend==SOCKET_ERROR){ cout<<"Error at send()."<<endl; return 1; } bytesLeft-=bytesSend; idx+=bytesSend; } return 0; } int GetFileLen(FILE *fp){ // ?????? if(fp==NULL){ cout<<"Invalid argument. Error at GetFileLen()."<<endl; exit(0); } fseek(fp, 0, SEEK_END); int tempFileLen=ftell(fp); fseek(fp, 0, SEEK_SET); return tempFileLen; } int main(){ int err; sockaddr_in addrServ; int port=8000; // Initialize Winsock WinsockInitial(); // Create a socket SOCKET sockListen=socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); if(sockListen==INVALID_SOCKET){ cout<<"Error at socket()."<<endl; WSACleanup(); return 1; } // Bind the socket. SockBind(sockListen, port, addrServ); // Listen for incoming connection requests cout<<"Waiting for incoming connection requests..."<<endl; SockListen(sockListen, 5); // Accept the connection request. sockaddr_in addrClient; int len=sizeof(addrClient); SOCKET sockConn=accept(sockListen, (sockaddr*)&addrClient, &len); if(sockConn!=INVALID_SOCKET){ cout<<"Connected to client successfully."<<endl; } // Set the buffer size of socket char sockBuf[SOCKKET_BUFFER_SIZE]; int nBuf=SOCKKET_BUFFER_SIZE; int nBufLen=sizeof(nBuf); err=setsockopt(sockConn, SOL_SOCKET, SO_SNDBUF, (char*)&nBuf, nBufLen); if(err!=0){ cout<<"Error at setsockopt(). Failed to set buffer size for socket."<<endl; exit(0); } //??????????? err = getsockopt(sockConn, SOL_SOCKET, SO_SNDBUF, (char*)&nBuf, &nBufLen); if( SOCKKET_BUFFER_SIZE != nBuf){ cout<<"Error at setsockopt(). ?socket????????"<<endl; closesocket(sockListen); closesocket(sockConn); WSACleanup(); exit(0); } //------------------------------------------------------------------------// DataPack dataPackSend; memset(&dataPackSend, 0, sizeof(dataPackSend)); int bytesRead; int bytesLeft; int bytesSend; int packCount; // Counts how many DataPack needed FILE *frp; // Used to read if(strcpy_s(dataPackSend.fName, "music.mp3")!=0){ cout<<"Error at strcpy_s()."<<endl; return 1; } // Open the file in read+binary mode err=fopen_s(&frp, dataPackSend.fName, "rb"); if(err!=0){ cout<<"Error at fopen_s()."<<endl; return 1; } char fileBuf[FILE_BUFFER_SIZE]; // Set the buffer size of File if(setvbuf(frp, fileBuf, _IONBF, FILE_BUFFER_SIZE)!=0){ cout<<"Error at setvbuf().Failed to set buffer size for file."<<endl; closesocket(sockListen); closesocket(sockConn); WSACleanup(); exit(0); } // Get file's length int fileLen=GetFileLen(frp); cout<<"File ???:"<<fileLen<<" bytes."<<endl; // Calculate how many DataPacks needed packCount=ceil( (double)fileLen/CONTENT_SIZE ); cout<<"File Length: "<<fileLen<<" "<<"Content Size: "<<CONTENT_SIZE<<endl; cout<<"???"<<packCount<<" ?DataPack"<<endl; int i=0; for(i=0; i<packCount; i++){ //?????dataPackSend????? memset(&dataPackSend, 0, sizeof(dataPackSend)); // Fill the dataPackSend if(strcpy_s(dataPackSend.fName, "abc.txt")!=0){ cout<<"Error at strcpy_s()."<<endl; return 1; } dataPackSend.packLen=DATA_PACK_SIZE; dataPackSend.fLen=fileLen; dataPackSend.packCount=packCount; if( packCount==1 ){ //??DataPack??? bytesRead=fread(fileBuf, 1, dataPackSend.fLen, frp); dataPackSend.contenLen=dataPackSend.fLen; memcpy(dataPackSend.content, fileBuf, bytesRead); dataPackSend.packNum=0; //???????DataPack // ?????dataPackSend?Client? if( SockSend(dataPackSend, sockConn, sockBuf)==0 ){ cout<<"??? "<<dataPackSend.packNum<<" ?DataPack"<<endl; } }else if( packCount>1 && i<(packCount-1) ){ // ???(???????) bytesRead=fread(fileBuf, 1, CONTENT_SIZE, frp); dataPackSend.contenLen=CONTENT_SIZE; memcpy(dataPackSend.content, fileBuf, bytesRead); dataPackSend.packNum=i; //?dataPackSend??????Client? if( SockSend(dataPackSend, sockConn, sockBuf)==0 ){ cout<<"??? "<<dataPackSend.packNum<<" ?DataPack."<<endl; } }else{ // ????? bytesRead=fread(fileBuf, 1, (dataPackSend.fLen-i*CONTENT_SIZE), frp); dataPackSend.contenLen=dataPackSend.fLen-i*CONTENT_SIZE; memcpy(dataPackSend.content, fileBuf, bytesRead); dataPackSend.packNum=i; //?dataPackSend???Client? if( SockSend(dataPackSend, sockConn, sockBuf)==0 ){ cout<<"??? "<<dataPackSend.packNum<<" ?DataPack."<<endl; } } } fclose(frp); closesocket(sockListen); closesocket(sockConn); WSACleanup(); return 0; } And this is Client. #include <WinSock2.h> #include <memory.h> #include <stdio.h> #include <iostream> using namespace std; #pragma comment(lib, "ws2_32.lib") #define MAX_FILE_NAME 100 #define DATA_PACK_SIZE 80*1000 // ??DataPack?????80KB #define SOCKKET_BUFFER_SIZE 80*1000 // socket??? #define FILE_BUFFER_SIZE DATA_PACK_SIZE-MAX_FILE_NAME-4*sizeof(int)-sizeof(u_long) //?????,??,??????content????? #define CONTENT_SIZE FILE_BUFFER_SIZE // DataPack?????content??? // Define a structure to hold the content of a file typedef struct FilePack{ char fName[MAX_FILE_NAME]; // File's name int fLen; // File's length int packNum; // Number of the DataPack int packLen; // DataPack's length int packCount; //DataPack??? int contenLen; // the content length the DataPack actually holds u_long index; // ?????????? char content[CONTENT_SIZE]; // DataPack?????? }DataPack, *pDataPack; void WinsockInitial(){ WSADATA wsaData; WORD wVersionRequested; int err; wVersionRequested=MAKEWORD(2,2); err=WSAStartup(wVersionRequested, &wsaData); if(err!=0){ cout<<"Error at WSAStartup()."<<endl; exit(0); } if( LOBYTE(wsaData.wVersion)!=2 || HIBYTE(wsaData.wVersion)!=2 ){ cout<<"Error at version of Winsock. "<<endl; WSACleanup(); exit(0); } } int SockRecv(SOCKET sock, char *sockBuf){ int bytesLeft, bytesRecv; int idx=0; bytesLeft=DATA_PACK_SIZE; while(bytesLeft>0){ bytesRecv=recv(sock, &sockBuf[idx], bytesLeft, 0); if(bytesRecv==SOCKET_ERROR){ cout<<"Error at recv()."<<endl; return 1; } bytesLeft-=bytesRecv; idx+=bytesRecv; } return 0; } int main(){ int err; sockaddr_in addrServ; int port=8000; // Initialize Winsock WinsockInitial(); // Create a socket SOCKET sockClient=socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); if(sockClient==INVALID_SOCKET){ cout<<"Error at socket()."<<endl; WSACleanup(); return 1; } // Set the buffer size of socket char sockBuf[SOCKKET_BUFFER_SIZE]; int nBuf=SOCKKET_BUFFER_SIZE; int nBufLen=sizeof(nBuf); err=setsockopt(sockClient, SOL_SOCKET, SO_RCVBUF, (char*)&nBuf, nBufLen); if(err!=0){ cout<<"Error at setsockopt(). Failed to set buffer size for socket."<<endl; exit(0); } //??????????? err = getsockopt(sockClient, SOL_SOCKET, SO_RCVBUF, (char*)&nBuf, &nBufLen); if( SOCKKET_BUFFER_SIZE != nBuf){ cout<<"Error at getsockopt(). ?socket????????"<<endl; closesocket(sockClient); WSACleanup(); exit(0); } // Connect to the Server addrServ.sin_family=AF_INET; addrServ.sin_port=htons(port); addrServ.sin_addr.S_un.S_addr=inet_addr("127.0.0.1"); err=connect(sockClient, (sockaddr*)&addrServ, sizeof(sockaddr)); if(err==SOCKET_ERROR){ cout<<"Error at connect()."<<GetLastError()<<endl; closesocket(sockClient); WSACleanup(); return 1; }else{ cout<<"Connected to the FTP Server successfully."<<endl; } /* int i=0; int bytesRecv, bytesLeft, bytesWrite; int packCount=0, fLen=0; DataPack dataPackRecv; //?????? SockRecv(sockClient, sockBuf); memcpy(&dataPackRecv, sockBuf, sizeof(dataPackRecv)); cout<<"???? "<<dataPackRecv.packNum<<" ?DataPack."<<endl; cout<<"?DataPack??fName????: "<<dataPackRecv.fName<<endl; //??????? packCount=dataPackRecv.packCount; cout<<"?? "<<packCount<<" ?DataPack."<<endl; fLen=dataPackRecv.fLen; // Create a local file to write into FILE *fwp; err=fopen_s(&fwp, dataPackRecv.fName, "wb"); if(err!=0){ cout<<"Error at creat fopen_s(). Failed to create a local file to write into."<<endl; return 1; } // Set the buffer size of File char fileBuf[FILE_BUFFER_SIZE]; if(setvbuf(fwp, fileBuf, _IONBF, FILE_BUFFER_SIZE)!=0){ cout<<"Error at setvbuf().Failed to set buffer size for file."<<endl; memset(fileBuf, 0, sizeof(fileBuf)); closesocket(sockClient); WSACleanup(); exit(0); } //???????content???? memcpy(fileBuf, dataPackRecv.content, sizeof(dataPackRecv.content)); bytesWrite=fwrite(fileBuf, 1, sizeof(fileBuf), fwp); if(bytesWrite<sizeof(fileBuf)){ cout<<"Error at fwrite(). Failed to write the content of dataPackRecv to local file."<<endl; } //?????packCount-1????????????????? for(int i=1; i<packCount; i++){ // ????????? memset(sockBuf, 0, sizeof(sockBuf)); memset(&dataPackRecv, 0, sizeof(dataPackRecv)); memset(fileBuf, 0, sizeof(fileBuf)); SockRecv(sockClient, sockBuf); memcpy(&dataPackRecv, sockBuf, sizeof(dataPackRecv)); cout<<"???? "<<dataPackRecv.packNum<<" ?DataPack."<<endl; //???? memcpy(fileBuf, dataPackRecv.content, dataPackRecv.contenLen); bytesWrite=fwrite(fileBuf, 1, dataPackRecv.contenLen, fwp); if(bytesWrite<dataPackRecv.contenLen){ cout<<"Error at fwrite(). Failed to write the content of dataPackRecv to local file."<<endl; } } if( (i+1)==packCount ){ cout<<"??DataPack????????!"<<endl; } fclose(fwp); closesocket(sockClient); WSACleanup(); return 0;*/ }

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  • Brute force algorithm implemented for sudoku solver in C [closed]

    - by 0cool
    This is my code that I have written in C.. It could solve certain level of problems but not the harder one.. I could not locate the error in it, Can you please find that.. # include <stdio.h> # include "sudoku.h" extern int sudoku[size][size]; extern int Arr[size][size]; int i, j, n; int BruteForceAlgorithm (void) { int val; for (i=0; i<size; i++) { for (j=0; j<size; j++) { if (sudoku[i][j]==0) { for (n=1; n<nmax; n++) { val = check (i,j,n); if ( val == 1) { sudoku[i][j]=n; // output(); break; } else if ( val == 0 && n == nmax-1 ) get_back(); } } } } } int get_back (void) { int p,q; int flag=0; for ( p=i; p>=0; p-- ) { for (q=j; q>=0; q-- ) { flag=0; if ( Arr[p][q]==0 && !( p==i && q==j) ) { if ( sudoku[p][q]== nmax-1 ) sudoku[p][q]=0; else { n = sudoku[p][q]; sudoku[p][q]=0; i = p; j = q; flag = 1; break; } } } if ( flag == 1) break; } } Code description: Sudoku.h has definitions related to sudoku solver. 1. size = 9 nmax = 10 2. check(i,j,n) returns 1 if a number "n" can be placed at (i,j) or else "0". What does this code do ? The code starts iterating from sudoku[0][0] to the end... if it finds a empty cell ( we take cell having "0" ), it starts checking for n=1 to n=9 which can be put in that.. as soon as a number can be put in that which is checked by check() it assigns it and breaks from loop and starts finding another empty cell. In case for a particular cell if it doesn't find "n" which can be assigned to sudoku cell.. it goes back to the previous empty cell and start iterating from where it stopped and assigns the next value and continues, Here comes the function get_back(). it iterates back..

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  • high virtual memory usage in openvz?

    - by freedrull
    We're having a lot of memory problems on a new OpenVZ box. It is supposed to have 1 gig of memory, I'm not sure how much of that is burstable or guaranteed memory. Programs in general seem to take up more virtual memory than they do on my box at home, and on our other OpenVZ box. I wrote this simple C program: #include <stdio.h> #include <stdlib.h> int main(){ char *thingy = malloc(500); getchar(): return 0; } So it simply allocates 500 bytes and then returns. I ran the program on 3 computers. On my home machine, and our other OpenVZ box it shows about 1k bytes of virtual memory being used. On the new problematic machine its about 3k. I know this is just virtual memory and not resident memory, but why is this machine allocating so much virtual memory? Are there some settings I need to adjust to the OpenVZ memory settings? I tried changing the stack size with ulimit -s 256 and restarting some demons, but I still saw the same results. I'm doing all of my monitoring with htop, is this even a good program to use with a OpenVZ vps? I've read I should be parsing the output of /proc/user_beancounters intead or something.

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  • Problems using Mesa demos

    - by Rodnower
    Hello, I successfully installed Mesa with "yum install Mesa*" and downloaded MesaDemos-7.8.tar.gz archive. Now I try follow instructions from "Mesa3d.org - Download / Insall - Compiling and Installing - 1.5 Running the demos", but in progs/demos there is only *.c files, when I try to compile them, I get many similar errors like: gears.c:(.text+0x54): undefined reference to `glShadeModel' I guess that this is very noob question, and I understand that there is very simple solution, but I haven't any idea... In beggining of the file there are all necessary #includes: #include <math.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #include <GL/glut.h> So I have some questions: Is there some Mesa forum on the web? Is there some compiled demos? Is there some site with well described examples of Mesa using? What I need for compile those examples? I have CentOS 5 Thank you for ahead.

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  • Font for Wine that supports the entire character set of the Win32 Console?

    - by Brian Campbell
    I would like to be able to display in the Wine console all characters that the Win32 console can display. I've written a small test program to print out all 8-bit characters: #include <stdio.h> int main(int argc, char *argv[]) { int i, j; for (i = 0; i <= 0xF0; i+=0x10) { for (j = i; j <= i + 0x0F; ++j) printf("%2x:%c", j, (char)j); printf("\n"); } getchar(); return 0; } Under Wine, the best I can do so far is using Andale Mono: While this is what I see on Windows Server 2008: Is there anywhere I can legally download a font that will allow me to view all of those characters under Wine? edit I've found a set of DOS fonts that includes a CP437 font, which should cover the character set I'm interested in. However, even if I install this font, wineconsole doesn't seem to recognize it. Is there any way I can get wineconsole to use this font, or convert this font to a format that wineconsole can use? Or is there any way I can extract fonts from DOSEMU for use in Wine? Oh, and I should probably mention that I'm on Mac OS X 10.6.2, installing Wine via MacPorts, using the wine-devel package. more information I have tried installing some console fonts that should cover the full character set as Mac OS X fonts (such as the NewDOS font listed above, and a font I tried converting from the fonts supplied by DOSEMU). Wine does not seem to pick up on new fonts installed in Mac OS X. Is there a way to register new fonts I've installed with Wine? Would manually editing the system.reg file that seems to contain font mappings work, or is there something else I'd need to do? bump Bounty ends soon, I'm still looking for an answer for this. Does anyone use the Wine console for complex text user interfaces?

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  • libstdc++ - compiling failing because of tr1/regex

    - by Radek Šimko
    I have these packages installed on my OpenSUSE 11.3: i | libstdc++45 | Standard shared library for C++ | package i | libstdc++45-devel | Contains files and libraries for development | package But when i'm trying to compile this C++ code: #include <stdio.h> #include <tr1/regex> using namespace std; int main() { int test[2]; const tr1::regex pattern(".*"); test[0] = 1; if (tr1::regex_match("anything", pattern) == false) { printf("Pattern does not match.\n"); } return 0; } using g++ -pedantic -g -O1 -o ./main.o ./main.cpp It outputs this errors: ./main.cpp: In function ‘int main()’: ./main.cpp:13:43: error: ‘printf’ was not declared in this scope radek@mypc:~> nano main.cpp radek@mypc:~> g++ -pedantic -g -O1 -o ./main.o ./main.cpp /tmp/cc0g3GUE.o: In function `basic_regex': /usr/include/c++/4.5/tr1_impl/regex:771: undefined reference to `std::tr1::basic_regex<char, std::tr1::regex_traits<char> >::_M_compile()' /tmp/cc0g3GUE.o: In function `bool std::tr1::regex_match<char const*, char, std::tr1::regex_traits<char> >(char const*, char const*, std::tr1::basic_regex<char, std::tr1::regex_traits<char> > const&, std::bitset<11u>)': /usr/include/c++/4.5/tr1_impl/regex:2144: undefined reference to `bool std::tr1::regex_match<char const*, std::allocator<std::tr1::sub_match<char const*> >, char, std::tr1::regex_traits<char> >(char const*, char const*, std::tr1::match_results<char const*, std::allocator<std::tr1::sub_match<char const*> > >&, std::tr1::basic_regex<char, std::tr1::regex_traits<char> > const&, std::bitset<11u>)' collect2: ld returned 1 exit status What packages should i (un)install to make the code work on my PC?

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  • Linux Scheduler (not using all cores on multi-core machine) RHEL6

    - by User512
    I'm seeing strange behavior on one of my servers (running RHEL 6). There seems to be something wrong with the scheduler. Here's the test program I'm using: #include <stdio.h> #include <unistd.h> #include <stdlib.h> void RunClient(int i) { printf("Starting client %d\n", i); while (true) { } } int main(int argc, char** argv) { for (int i = 0; i < 4; ++i) { pid_t p_id = fork(); if (p_id == -1) { perror("fork"); } else if (p_id == 0) { RunClient(i); exit(0); } } return 0; } This machine has a lot more than 4 cores so we'd expect all processes to be running at 100%. When I check on top, the cpu usage varies. Sometimes it's split (100%, 33%, 33%, 33%), other times it's split (100%, 100%, 50%, 50%). When I try this test on another server of ours (running RHEL 5), there are no issues (it's 100%, 100%, 100%, 100%) as expected. What's causing this and how can I fix it? Thanks

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  • How to know if the client has terminated in sockets

    - by shadyabhi
    Suppose, I have a connected socket after writing this code.. if ((sd = accept(socket_d, (struct sockaddr *)&client_addr, &alen)) < 0) { perror("accept failed\n"); exit(1); } How can I know at the server side that client has exited. My whole program actually does the following.. Accepts a connection from client Starts a new thread that reads messages from that particular client and then broadcast this message to all the connected clients. If you want to see the whole code... In this whole code. I am also struggling with one more problem that whenever I kill a client with Ctrl+C, my server terminates abruptly.. It would be nice if anyone could suggest what the problem is.. #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <signal.h> #include <errno.h> #include <pthread.h> /*CONSTANTS*/ #define DEFAULT_PORT 10000 #define LISTEN_QUEUE_LIMIT 6 #define TOTAL_CLIENTS 10 #define CHAR_BUFFER 256 /*GLOBAL VARIABLE*/ int current_client = 0; int connected_clients[TOTAL_CLIENTS]; extern int errno; void *client_handler(void * socket_d); int main(int argc, char *argv[]) { struct sockaddr_in server_addr;/* structure to hold server's address*/ int socket_d; /* listening socket descriptor */ int port; /* protocol port number */ int option_value; /* needed for setsockopt */ pthread_t tid[TOTAL_CLIENTS]; port = (argc > 1)?atoi(argv[1]):DEFAULT_PORT; /* Socket Server address structure */ memset((char *)&server_addr, 0, sizeof(server_addr)); server_addr.sin_family = AF_INET; /* set family to Internet */ server_addr.sin_addr.s_addr = INADDR_ANY; /* set the local IP address */ server_addr.sin_port = htons((u_short)port); /* Set port */ /* Create socket */ if ( (socket_d = socket(PF_INET, SOCK_STREAM, 0)) < 0) { fprintf(stderr, "socket creation failed\n"); exit(1); } /* Make listening socket's port reusable */ if (setsockopt(socket_d, SOL_SOCKET, SO_REUSEADDR, (char *)&option_value, sizeof(option_value)) < 0) { fprintf(stderr, "setsockopt failure\n"); exit(1); } /* Bind a local address to the socket */ if (bind(socket_d, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) { fprintf(stderr, "bind failed\n"); exit(1); } /* Specify size of request queue */ if (listen(socket_d, LISTEN_QUEUE_LIMIT) < 0) { fprintf(stderr, "listen failed\n"); exit(1); } memset(connected_clients,0,sizeof(int)*TOTAL_CLIENTS); for (;;) { struct sockaddr_in client_addr; /* structure to hold client's address*/ int alen = sizeof(client_addr); /* length of address */ int sd; /* connected socket descriptor */ if ((sd = accept(socket_d, (struct sockaddr *)&client_addr, &alen)) < 0) { perror("accept failed\n"); exit(1); } else printf("\n I got a connection from (%s , %d)\n",inet_ntoa(client_addr.sin_addr),ntohs(client_addr.sin_port)); if (pthread_create(&tid[current_client],NULL,(void *)client_handler,(void *)sd) != 0) { perror("pthread_create error"); continue; } connected_clients[current_client]=sd; current_client++; /*Incrementing Client number*/ } return 0; } void *client_handler(void *connected_socket) { int sd; sd = (int)connected_socket; for ( ; ; ) { ssize_t n; char buffer[CHAR_BUFFER]; for ( ; ; ) { if (n = read(sd, buffer, sizeof(char)*CHAR_BUFFER) == -1) { perror("Error reading from client"); pthread_exit(1); } int i=0; for (i=0;i<current_client;i++) { if (write(connected_clients[i],buffer,sizeof(char)*CHAR_BUFFER) == -1) perror("Error sending messages to a client while multicasting"); } } } } My client side is this (Maye be irrelevant while answering my question) #include <stdio.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <netdb.h> #include <string.h> #include <stdlib.h> void error(char *msg) { perror(msg); exit(0); } void *listen_for_message(void * fd) { int sockfd = (int)fd; int n; char buffer[256]; bzero(buffer,256); printf("YOUR MESSAGE: "); fflush(stdout); while (1) { n = read(sockfd,buffer,256); if (n < 0) error("ERROR reading from socket"); if (n == 0) pthread_exit(1); printf("\nMESSAGE BROADCAST: %sYOUR MESSAGE: ",buffer); fflush(stdout); } } int main(int argc, char *argv[]) { int sockfd, portno, n; struct sockaddr_in serv_addr; struct hostent *server; pthread_t read_message; char buffer[256]; if (argc < 3) { fprintf(stderr,"usage %s hostname port\n", argv[0]); exit(0); } portno = atoi(argv[2]); sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) error("ERROR opening socket"); server = gethostbyname(argv[1]); if (server == NULL) { fprintf(stderr,"ERROR, no such host\n"); exit(0); } bzero((char *) &serv_addr, sizeof(serv_addr)); serv_addr.sin_family = AF_INET; bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->h_length); serv_addr.sin_port = htons(portno); if (connect(sockfd,&serv_addr,sizeof(serv_addr)) < 0) error("ERROR connecting"); bzero(buffer,256); if (pthread_create(&read_message,NULL,(void *)listen_for_message,(void *)sockfd) !=0 ) { perror("error creating thread"); } while (1) { fgets(buffer,255,stdin); n = write(sockfd,buffer,256); if (n < 0) error("ERROR writing to socket"); bzero(buffer,256); } return 0; }

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  • How to debug a kernel created using ubuntu-vm-builder?

    - by user265592
    Aim: Trying to perform a code walkthrough of what functions are getting called for sending and receiving packets over the network. I am building a kernel and using gdb for debugging/ tracing purposes. I have build a vm using the following command : time sudo ubuntu-vm-builder qemu precise --arch 'amd64' --mem '1024' --rootsize '4096' --swapsize '1024' --kernel-flavour 'generic' --hostname 'ubuntu' --components 'main' --name 'Bob' --user 'ubuntu' --pass 'ubuntu' --bridge 'br0' --libvirt 'qemu:///system' And I can run the VM successfully in qemu using the following command: qemu-system-x86_64 -smp 1 -drive file=tmpGgEOzK.qcow2 "$@" -net nic -net user -serial stdio -redir tcp:2222::22 Now, I want to debug the kernel using gdb. For this I need an executable with debug symbols(vmlinux), which apparently I don't have, as the vm-builder never asked for any such options and simply created a .qcow2 file. Question 1: Am I taking the correct approach to solve the problem and is there an easier way to do it? Question 2: Is there a way to debug this kernel using GDB? P.S: I don't have hardware support for KVM. Please correct me if I am wrong. Thanks.

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  • cannot delete from doubly linked list using visual studios in C

    - by Jesus Sanchez
    hello I am currently doing an assignment that is supposed to read in a file, use the information, and then print out another file. all using doubly linked list. Currently i am trying to just read in the file into a doubly linked list, print it out onto the screen and a file, and finally delete the list and close the program. The program works fine as long as I don't call the dlist_distroy function which is supposed to delete the string. as soon as I do it the program starts running and then a window pops up saying "Windows has triggered a breakpoint in tempfilter.exe. This may be due to a corruption of the heap, which indicates a bug in tempfilter.exe or any of the DLLs it has loaded. This may also be due to the user pressing F12 while tempfilter.exe has focus. The output window may have more diagnostic information." I have revised the destroy and remove functions and cant understand the problem. my program is the following main.c #include <stdlib.h> #include <stdio.h> #include <string.h> #include "dlinklist.h" #include "DlistElmt.h" #include "Dlist.h" #include "dlistdata.h" /**************************************************************************************************/ int main ( int argc, char *argv[] ) { FILE *ifp, *ofp; int hour, min; Dlist *list; DlistElmt *current=NULL, *element; float temp; list = (Dlist *)malloc(sizeof(list)); element = (DlistElmt *)malloc(sizeof(element)); if ( argc != 3 ) /* argc should be 3 for correct execution */ { /* We print argv[0] assuming it is the program name */ /* TODO: This is wrong, it should be: usage: %s inputfile outputfile */ printf( "usage: %s filename", argv[0] ); } else { // We assume argv[1] is a filename to open ifp = fopen( argv[1], "r" ); if (ifp == 0 ){ printf("Could not open file\n"); } else{ ofp = fopen(argv[2], "w"); dlist_init(list);//, (destroy)(hour, min, temp)); while (fscanf(ifp, "%d:%d %f ", &hour, &min, &temp) == 3) { current=list->tail; if(dlist_size(list)==0){ dlist_ins_prev(list, current, hour, min, temp); } else{ dlist_ins_next(list, current, hour, min, temp); } } current = list->head; while(current != NULL){ if(current==list->head){ current=current->next; } else if((current->temp > (current->prev->temp +5)) || (current->temp < (current->prev->temp -5))){ dlist_remove(list, current); current=current->next; } else current=current->next; } current = list->head; while(current != NULL){ printf("%d:%d %2.1lf\n" ,current->time, current->time2, current->temp ); fprintf(ofp, "%d:%d %2.1lf\n", current->time, current->time2, current->temp ); current = current->next; } //dlist_destroy(list); //} fclose(ifp); fclose(ofp); } } getchar(); } dlistdata.c #include <stdlib.h> #include <stdio.h> #include <string.h> #include "dlinklist.h" #include "DlistElmt.h" #include "dlistdata.h" /**************************************************************************************************/ void dlist_init(Dlist *list){ list->size = 0; list->head = NULL; list->tail = NULL; return; } void dlist_destroy(Dlist *list){ while (dlist_size(list) > 0){ dlist_remove(list, list->head); } memset(list, 0, sizeof(Dlist)); return; } int dlist_ins_next(Dlist *list, DlistElmt *element, const int time, const int time2, const float temp){ DlistElmt *new_element; if (element == NULL && dlist_size(list) != 0) return -1; if ((new_element = (DlistElmt *)malloc(sizeof(new_element))) == NULL) return -1; new_element->time = (int )time; new_element->time2 = (int )time2; new_element->temp = (float )temp; if (dlist_size(list) == 0) { list->head = new_element; list->head->prev = NULL; list->head->next = NULL; list->tail = new_element; } else { new_element->next = element->next; new_element->prev = element; if(element->next == NULL) list->tail = new_element; else element->next->prev = new_element; element->next = new_element; } list->size++; return 0; } int dlist_ins_prev(Dlist *list, DlistElmt *element, const int time, const int time2, const float temp){ DlistElmt *new_element; if (element == NULL && dlist_size(list) != 0) return -1; if ((new_element = (DlistElmt *)malloc(sizeof(new_element))) == NULL) return -1; new_element->time = (int )time; new_element->time2 = (int )time2; new_element->temp = (float )temp; if (dlist_size(list) == 0){ list->head = new_element; list->head->prev = NULL; list->head->next=NULL; list->tail = new_element; } else{ new_element->next = element; new_element->prev = element->prev; if(element->prev ==NULL) list->head = new_element; else element->prev->next = new_element; element->prev = new_element; } list->size++; return 0; } int dlist_remove(Dlist *list, DlistElmt *element){//, int time, int time2, float temp){ if (element == NULL || dlist_size(list) == 0) return -1; if (element == list->head) { list->head = element->next; if (list->head == NULL) list->tail = NULL; else element->next->prev = NULL; } else{ element->prev->next = element->next; if (element->next = NULL) list->tail = element->prev; else element->next->prev = element->prev; } free(element); list->size--; return 0; }

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  • C sockets, chat server and client, problem echoing back.

    - by wretrOvian
    Hi This is my chat server : #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netdb.h> #include <string.h> #define LISTEN_Q 20 #define MSG_SIZE 1024 struct userlist { int sockfd; struct sockaddr addr; struct userlist *next; }; int main(int argc, char *argv[]) { // declare. int listFD, newFD, fdmax, i, j, bytesrecvd; char msg[MSG_SIZE], ipv4[INET_ADDRSTRLEN]; struct addrinfo hints, *srvrAI; struct sockaddr_storage newAddr; struct userlist *users, *uptr, *utemp; socklen_t newAddrLen; fd_set master_set, read_set; // clear sets FD_ZERO(&master_set); FD_ZERO(&read_set); // create a user list users = (struct userlist *)malloc(sizeof(struct userlist)); users->sockfd = -1; //users->addr = NULL; users->next = NULL; // clear hints memset(&hints, 0, sizeof hints); // prep hints hints.ai_family = AF_INET; hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; // get srver info if(getaddrinfo("localhost", argv[1], &hints, &srvrAI) != 0) { perror("* ERROR | getaddrinfo()\n"); exit(1); } // get a socket if((listFD = socket(srvrAI->ai_family, srvrAI->ai_socktype, srvrAI->ai_protocol)) == -1) { perror("* ERROR | socket()\n"); exit(1); } // bind socket bind(listFD, srvrAI->ai_addr, srvrAI->ai_addrlen); // listen on socket if(listen(listFD, LISTEN_Q) == -1) { perror("* ERROR | listen()\n"); exit(1); } // add listfd to master_set FD_SET(listFD, &master_set); // initialize fdmax fdmax = listFD; while(1) { // equate read_set = master_set; // run select if(select(fdmax+1, &read_set, NULL, NULL, NULL) == -1) { perror("* ERROR | select()\n"); exit(1); } // query all sockets for(i = 0; i <= fdmax; i++) { if(FD_ISSET(i, &read_set)) { // found active sockfd if(i == listFD) { // new connection // accept newAddrLen = sizeof newAddr; if((newFD = accept(listFD, (struct sockaddr *)&newAddr, &newAddrLen)) == -1) { perror("* ERROR | select()\n"); exit(1); } // resolve ip if(inet_ntop(AF_INET, &(((struct sockaddr_in *)&newAddr)->sin_addr), ipv4, INET_ADDRSTRLEN) == -1) { perror("* ERROR | inet_ntop()"); exit(1); } fprintf(stdout, "* Client Connected | %s\n", ipv4); // add to master list FD_SET(newFD, &master_set); // create new userlist component utemp = (struct userlist*)malloc(sizeof(struct userlist)); utemp->next = NULL; utemp->sockfd = newFD; utemp->addr = *((struct sockaddr *)&newAddr); // iterate to last node for(uptr = users; uptr->next != NULL; uptr = uptr->next) { } // add uptr->next = utemp; // update fdmax if(newFD > fdmax) fdmax = newFD; } else { // existing sockfd transmitting data // read if((bytesrecvd = recv(i, msg, MSG_SIZE, 0)) == -1) { perror("* ERROR | recv()\n"); exit(1); } msg[bytesrecvd] = '\0'; // find out who sent? for(uptr = users; uptr->next != NULL; uptr = uptr->next) { if(i == uptr->sockfd) break; } // resolve ip if(inet_ntop(AF_INET, &(((struct sockaddr_in *)&(uptr->addr))->sin_addr), ipv4, INET_ADDRSTRLEN) == -1) { perror("* ERROR | inet_ntop()"); exit(1); } // print fprintf(stdout, "%s\n", msg); // send to all for(j = 0; j <= fdmax; j++) { if(FD_ISSET(j, &master_set)) { if(send(j, msg, strlen(msg), 0) == -1) perror("* ERROR | send()"); } } } // handle read from client } // end select result handle } // end looping fds } // end while return 0; } This is my client: #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netdb.h> #include <string.h> #define MSG_SIZE 1024 int main(int argc, char *argv[]) { // declare. int newFD, bytesrecvd, fdmax; char msg[MSG_SIZE]; fd_set master_set, read_set; struct addrinfo hints, *srvrAI; // clear sets FD_ZERO(&master_set); FD_ZERO(&read_set); // clear hints memset(&hints, 0, sizeof hints); // prep hints hints.ai_family = AF_INET; hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; // get srver info if(getaddrinfo(argv[1], argv[2], &hints, &srvrAI) != 0) { perror("* ERROR | getaddrinfo()\n"); exit(1); } // get a socket if((newFD = socket(srvrAI->ai_family, srvrAI->ai_socktype, srvrAI->ai_protocol)) == -1) { perror("* ERROR | socket()\n"); exit(1); } // connect to server if(connect(newFD, srvrAI->ai_addr, srvrAI->ai_addrlen) == -1) { perror("* ERROR | connect()\n"); exit(1); } // add to master, and add keyboard FD_SET(newFD, &master_set); FD_SET(STDIN_FILENO, &master_set); // initialize fdmax if(newFD > STDIN_FILENO) fdmax = newFD; else fdmax = STDIN_FILENO; while(1) { // equate read_set = master_set; if(select(fdmax+1, &read_set, NULL, NULL, NULL) == -1) { perror("* ERROR | select()"); exit(1); } // check server if(FD_ISSET(newFD, &read_set)) { // read data if((bytesrecvd = recv(newFD, msg, MSG_SIZE, 0)) < 0 ) { perror("* ERROR | recv()"); exit(1); } msg[bytesrecvd] = '\0'; // print fprintf(stdout, "%s\n", msg); } // check keyboard if(FD_ISSET(STDIN_FILENO, &read_set)) { // read data from stdin if((bytesrecvd = read(STDIN_FILENO, msg, MSG_SIZE)) < 0) { perror("* ERROR | read()"); exit(1); } msg[bytesrecvd] = '\0'; // send if((send(newFD, msg, bytesrecvd, 0)) == -1) { perror("* ERROR | send()"); exit(1); } } } return 0; } The problem is with the part where the server recv()s data from an FD, then tries echoing back to all [send() ]; it just dies, w/o errors, and my client is left looping :(

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  • Can't seem to get C TCP Server-Client Communications Right

    - by Zeesponge
    Ok i need some serious help here. I have to make a TCP Server Client. When the Client connects to server using a three stage handshake. AFterwards... while the Client is running in the terminal, the user enters linux shell commands like xinput list, ls -1, ect... something that uses standard output. The server accepts the commands and uses system() (in a fork() in an infinite loop) to run the commands and the standard output is redirected to the client, where the client prints out each line. Afterward the server sends a completion signal of "\377\n". In which the client goes back to the command prompt asking for a new command and closes its connection and exit()'s when inputting "quit". I know that you have to dup2() both the STDOUT_FILENO and STDERR_FILENO to the clients file descriptor {dup2(client_FD, STDOUT_FILENO). Everything works accept when it comes for the client to retrieve system()'s stdout and printing it out... all i get is a blank line with a blinking cursor (client waiting on stdin). I tried all kinds of different routes with no avail... If anyone can help out i would greatly appreciate it TCP SERVER CODE include #include <sys/socket.h> #include <stdio.h> #include <string.h> #include <netinet/in.h> #include <signal.h> #include <unistd.h> #include <stdlib.h> #include <errno.h> //Prototype void handle_client(int connect_fd); int main() { int server_sockfd, client_sockfd; socklen_t server_len, client_len; struct sockaddr_in server_address; struct sockaddr_in client_address; server_sockfd = socket(AF_INET, SOCK_STREAM, 0); server_address.sin_family = AF_INET; server_address.sin_addr.s_addr = htonl(INADDR_ANY); server_address.sin_port = htons(9734); server_len = sizeof(server_address); bind(server_sockfd, (struct sockaddr *)&server_address, server_len); /* Create a connection queue, ignore child exit details and wait for clients. */ listen(server_sockfd, 10); signal(SIGCHLD, SIG_IGN); while(1) { printf("server waiting\n"); client_len = sizeof(client_address); client_sockfd = accept(server_sockfd, (struct sockaddr *)&client_address, &client_len); if(fork() == 0) handle_client(client_sockfd); else close(client_sockfd); } } void handle_client(int connect_fd) { const char* remsh = "<remsh>\n"; const char* ready = "<ready>\n"; const char* ok = "<ok>\n"; const char* command = "<command>\n"; const char* complete = "<\377\n"; const char* shared_secret = "<shapoopi>\n"; static char server_msg[201]; static char client_msg[201]; static char commands[201]; int sys_return; //memset client_msg, server_msg, commands memset(&client_msg, 0, sizeof(client_msg)); memset(&server_msg, 0, sizeof(client_msg)); memset(&commands, 0, sizeof(commands)); //read remsh from client read(connect_fd, &client_msg, 200); //check remsh validity from client if(strcmp(client_msg, remsh) != 0) { errno++; perror("Error Establishing Handshake"); close(connect_fd); exit(1); } //memset client_msg memset(&client_msg, 0, sizeof(client_msg)); //write remsh to client write(connect_fd, remsh, strlen(remsh)); //read shared_secret from client read(connect_fd, &client_msg, 200); //check shared_secret validity from client if(strcmp(client_msg, shared_secret) != 0) { errno++; perror("Invalid Security Passphrase"); write(connect_fd, "no", 2); close(connect_fd); exit(1); } //memset client_msg memset(&client_msg, 0, sizeof(client_msg)); //write ok to client write(connect_fd, ok, strlen(ok)); // dup2 STDOUT_FILENO <= client fd, STDERR_FILENO <= client fd dup2(connect_fd, STDOUT_FILENO); dup2(connect_fd, STDERR_FILENO); //begin while... while read (client_msg) from server and >0 while(read(connect_fd, &client_msg, 200) > 0) { //check command validity from client if(strcmp(client_msg, command) != 0) { errno++; perror("Error, unable to retrieve data"); close(connect_fd); exit(1); } //memset client_msg memset(&client_msg, 0, sizeof(client_msg)); //write ready to client write(connect_fd, ready, strlen(ready)); //read commands from client read(connect_fd, &commands, 200); //run commands using system( ) sys_return = system(commands); //check success of system( ) if(sys_return < 0) { perror("Invalid Commands"); errno++; } //memset commands memset(commands, 0, sizeof(commands)); //write complete to client write(connect_fd, complete, sizeof(complete)); } } TCP CLIENT CODE #include <sys/types.h> #include <sys/socket.h> #include <stdio.h> #include <string.h> #include <netinet/in.h> #include <arpa/inet.h> #include <unistd.h> #include <stdlib.h> #include <errno.h> #include "readline.c" int main(int argc, char *argv[]) { int sockfd; int len; struct sockaddr_in address; int result; const char* remsh = "<remsh>\n"; const char* ready = "<ready>\n"; const char* ok = "<ok>\n"; const char* command = "<command>\n"; const char* complete = "<\377\n"; const char* shared_secret = "<shapoopi>\n"; static char server_msg[201]; static char client_msg[201]; memset(&client_msg, 0, sizeof(client_msg)); memset(&server_msg, 0, sizeof(server_msg)); /* Create a socket for the client. */ sockfd = socket(AF_INET, SOCK_STREAM, 0); /* Name the socket, as agreed with the server. */ memset(&address, 0, sizeof(address)); address.sin_family = AF_INET; address.sin_addr.s_addr = inet_addr(argv[1]); address.sin_port = htons(9734); len = sizeof(address); /* Now connect our socket to the server's socket. */ result = connect(sockfd, (struct sockaddr *)&address, len); if(result == -1) { perror("ACCESS DENIED"); exit(1); } //write remsh to server write(sockfd, remsh, strlen(remsh)); //read remsh from server read(sockfd, &server_msg, 200); //check remsh validity from server if(strcmp(server_msg, remsh) != 0) { errno++; perror("Error Establishing Initial Handshake"); close(sockfd); exit(1); } //memset server_msg memset(&server_msg, 0, sizeof(server_msg)); //write shared secret text to server write(sockfd, shared_secret, strlen(shared_secret)); //read ok from server read(sockfd, &server_msg, 200); //check ok velidity from server if(strcmp(server_msg, ok) != 0 ) { errno++; perror("Incorrect security phrase"); close(sockfd); exit(1); } //? dup2 STDIN_FILENO = server socket fd? //dup2(sockfd, STDIN_FILENO); //begin while(1)/////////////////////////////////////// while(1){ //memset both msg arrays memset(&client_msg, 0, sizeof(client_msg)); memset(&server_msg, 0, sizeof(server_msg)); //print Enter Command, scan input, fflush to stdout printf("<<Enter Command>> "); scanf("%s", client_msg); fflush(stdout); //check quit input, if true close and exit successfully if(strcmp(client_msg, "quit") == 0) { printf("Exiting\n"); close(sockfd); exit(EXIT_SUCCESS); } //write command to server write(sockfd, command, strlen(command)); //read ready from server read(sockfd, &server_msg, 200); //check ready validity from server if(strcmp(server_msg, ready) != 0) { errno++; perror("Failed Server Communications"); close(sockfd); exit(1); } //memset server_msg memset(&server_msg, 0, sizeof(server_msg)); //begin looping and retrieving from stdin, //break loop at EOF or complete while((read(sockfd, server_msg, 200) != 0) && (strcmp(server_msg, complete) != 0)) { //while((fgets(server_msg, 4096, stdin) != EOF) || (strcmp(server_msg, complete) == 0)) { printf("%s", server_msg); memset(&server_msg, 0, sizeof(server_msg)); } } }

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