simple server & client getting Segmentation fault error

This is a discussion on simple server & client getting Segmentation fault error within the Linux Programming forums, part of the Platform Specific Boards category; I'm trying to make a server program that uses sockets and threads. I can get it to compile, but it ...

  1. #1
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    Question simple server & client getting Segmentation fault error

    I'm trying to make a server program that uses sockets and threads. I can get it to compile, but it keeps giving me a segmentation fault. I've made a number of changes to the program, and have no idea what is causing it. If anyone has an idea, please let me know. Here's the code, followed by the output i get. (Compiled using gcc) I've gotten the client code to work with the server code before I added the threads, but not now.

    Code:
    #include <sys/types.h>
    #include <sys/socket.h>
    #include <stdio.h>
    #include <netinet/in.h>
    #include <signal.h>
    #include <unistd.h>
    #include <pthread.h>
    
    void *thread_function(void *arg);
    
    int main ()
    {
    int res; /* for error checking */
    pthread_t client;
    void *thread_result;
    int j = 0; /* counter */
    int server_sockfd, client_sockfd;
    int 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);
    
    listen(server_sockfd, 5);
    
    signal(SIGCHLD, SIG_IGN);
    
    while(1) {
    client_len = sizeof(client_address);
    client_sockfd = accept(server_sockfd, (struct sockaddr *)&client_address, &client_len);
    printf("client_sockfd after accept call: %d\n", client_sockfd);
    if(client_sockfd < 0) {
    perror("server: accept error");
    exit(1);
    }
    printf("fixin to create pthread\n");
    res = pthread_create(&client, NULL, thread_function, (void *) client_sockfd);
    if(res != 0) {
    perror("Thread creation failed");
    exit(1);
    }
    printf("pthread created\n");
    res = pthread_join(client, &thread_result);
    printf("pthread joined?\n");
    if(res != 0) {
    perror("Thread join failed");
    exit(1);
    }
    printf("pthread joined.\n");
    }
    }
    
    void *thread_function(void *arg)
    {
    char ch;
    int sockfd;
    printf("inside thread_function\n");
    sockfd = *((int *)arg);
    printf("client_sockfd assigned: %d\n", sockfd);
    read(sockfd, &ch, 1);
    printf("char read: %c\n", ch);
    sleep(1);
    ch++;
    write(sockfd, &ch, 1);
    printf("char sent: %c\n", ch);
    close(sockfd);
    pthread_exit(1);
    }
    output:

    client_sockfd after accept call: 4
    fixin to create pthread
    inside thread_function
    pthread created
    char from server = z
    [1]+ Segmentation fault ./server4.exe

    (client code)
    Code:
    #include<sys/types.h>
    #include<sys/socket.h>
    #include<stdio.h>
    #include<netinet/in.h>
    #include<arpa/inet.h>
    #include<unistd.h>
    
    int main()
    {
    int sockfd;
    int len;
    
    struct sockaddr_in address;
    int result;
    char ch = 'A';
    
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = inet_addr("127.0.0.1");
    address.sin_port = htons(9734);
    len = sizeof(address);
    
    result = connect(sockfd, (struct sockaddr *)&address, len);
    
    if(result == -1) {
    perror("client1");
    exit(1);
    }
    
    write(sockfd, &ch, 1);
    ch = 'z';
    read(sockfd, &ch, 1);
    printf("char from server: %c\n", ch);
    close(sockfd);
    exit(0);
    }

  2. #2
    Registered User
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    Dec 2007
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    Sorry. I finally figured my problem out. I had an extra asterisk. *facepalm*

  3. #3
    and the hat of wrongness Salem's Avatar
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    Is your code that badly indented in your IDE ?
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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