Question

Linux GCC 4.4.2

I am doing some socket programming.

However, I keep getting this error when I try and assign the sockfd from the socket function.

" Socket operation on non-socket"

Many thanks for any advice,

#if defined(linux)
#include <pthread.h>
/* Socket specific functions and constants */
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <errno.h>
#endif

#include "server.h"
#include "cltsvr_ults.h"

/* Listens for a connection on the designated port */
void wait_client()
{
    struct addrinfo add_info, *add_res;
    int sockfd;

    /* Load up the address information using getaddrinfo to fill the struct addrinfo */
    memset(&add_info, 0, sizeof(add_info));
    /* Use either IPv4 or IPv6 */
    add_info.ai_family = AF_UNSPEC; 
    add_info.ai_socktype = SOCK_STREAM;
    /* Fill in my IP address */
    add_info.ai_flags = AI_PASSIVE;

    /* Fill the struct addrinfo */
    int32_t status = 0;
    if(status = getaddrinfo(NULL, "6000", &add_info, &add_res) != 0)
    {
        fprintf(stderr, "getaddrinfo [ %s ]\n", gai_strerror(status));

        return;
    }

    if((sockfd = (socket(add_res->ai_family, add_res->ai_socktype, add_res->ai_protocol)) == -1))
    {
        fprintf(stderr, "Socket failed [ %s ]\n", strerror(errno));

        return;
    }

    /* Bind to the port that has been assigned by getaddrinfo() */
    if(bind(sockfd, add_res->ai_addr, add_res->ai_addrlen) != 0)
    {
        fprintf(stderr, "Bind failed [ %s ]\n", strerror(errno));

        return;
    }

    printf("Listening for clients\n");
}

Edit == coding in the old-school method

    int32_t sockfd = 0;
    struct sockaddr_in my_addr;

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

    my_addr.sin_family = AF_INET;
    my_addr.sin_port = htons(6000);
    my_addr.sin_addr.s_addr = inet_addr("127.0.0.1");

    sockfd = socket(PF_INET, SOCK_STREAM, 0);
    if(sockfd == -1)
    {
    fprintf(stderr, "Socket failed [ %s ]\n", strerror(errno));
    return;
    }

    if(bind(sockfd, (struct sockaddr *) &my_addr, sizeof(my_addr)) == -1)
    {
    fprintf(stderr, "Bind failed [ %s ]\n", strerror(errno));
    return;
    }

Answer 1

Your main problem is that you have the wrong check for when socket() has an error. socket() will return -1 on error, not 0 on success. You may be getting a good socket value (2, 3, etc.) and treating it like an error.

There is also a second problem in the way you are parenthesizing your code. When you write:

if (sockfd = socket(add_res->ai_family, add_res->ai_socktype, add_res->ai_protocol) != 0)

That is being treated as:

if (sockfd = (socket(add_res->ai_family, add_res->ai_socktype, add_res->ai_protocol) != 0))

So sockfd will not be assigned the return value of socket, but the value of comparing it against 0. Fixing both problems, you should be writing:

if ((sockfd = socket(add_res->ai_family, add_res->ai_socktype, add_res->ai_protocol)) == -1)