Please help! Network programming error :/
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Thread: Please help! Network programming error :/

  1. #1
    Join Date
    Dec 2010

    Please help! Network programming error :/

    Hello everyone..

    I have a problem.. The main idea of my project is a server that accept client connections and everytime someone connects it checks if the client is available for reading or for writing with select() function.
    If is ready for writing then is send a buffer.. Well, this is a sample of code..

    FD_SET(fdmax, &master);
    for(; {
    read_fds = master;
    write_fds = master;

    if(select(fdmax + 1, &read_fds, &write_fds, NULL, NULL) == -1) {
    return -1;

    for(i = 0; i <= fdmax; i++) { // check through all socket

    if(FD_ISSET(i, &read_fds) != 0) {

    bla bla bla


    if(FD_ISSET(i, &write_fds)) { // teh client is ready for writing

    printf("send bytes: %ld\n", sizeof(jobs[counter]) );
    bytes = send(i, &jobs[counter], sizeof(jobs[counter]), 0);


    also the client source is..

    while(f == 0) {

    memset(&jobs, 0, sizeof(jobs));

    if((bytes = recv(sockfd, &jobs, sizeof(jobs), 0)) == -1) {
    printf("Error recving\n");


    bla bla bla

    the problem is that the server althougt is was supposed to send the msg only 1 time it is send it 10-15 times... it is like finds the client client all the time available for writing ( maybe i am doing sthng wrong with select and fds?).. Also the client exiting with segmentation fault JUST AFTER the printf function and i dunno why.. i suppose it is from the "oversending" of the packets from the server

    What should i do ? Thanks in advance..
    (i compiled it with gcc on Ubuntu distro)

  2. #2
    VictorN's Avatar
    VictorN is offline Super Moderator Power Poster
    Join Date
    Jan 2003
    Wallisellen (ZH), Switzerland

    Re: Please help! Network programming error :/

    Quote Originally Posted by Zisis View Post
    What should i do ? Thanks in advance..
    The first thing you have to do is edit your post to add Code tags around code snippets and proper code indentations inside the snippets. Otherwise your "code" is absolutely unreadable.

    See Announcement: Before you post....
    Victor Nijegorodov

  3. #3
    Join Date
    May 2001

    Re: Please help! Network programming error :/

    you have to re-initialise your read_fds and write_fds after select() returns, because they will be altered by the select() call.

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