Question

So I programmed a multi threaded web server, here is one function from the program. This function takes output file descriptor (fd), content type, pointer to data to be served (*buf) and size of the data (numbytes). It always gets stuck at 5775 bytes! I’ve tried using write() instead of send(), but no avail! I tried to send whole buf at a time, and even tried to transfer it in chunks, but wget shows that it gets stck at 5775 bytes! Here is the code:

int return_result(int fd, char *content_type, char *buf, int numbytes)
{
    char out_buf[BUF_SIZE], numb[6];
    int buf_len, total = 0, buf_size;
    long int i = 0;
    sprintf(numb, "%d", numbytes);
    strcpy(out_buf, "HTTP/1.1 200 OK \nContent-Type: ");
    strcat(out_buf, content_type);
    strcat(out_buf, "\nContent-Length: ");
    strcat(out_buf, numb);
    strcat(out_buf, "\nConnection: Close\n  \n");
    printf("\nSending HTTP Header\n %d bytes sent!",
           send(fd, out_buf, strlen(out_buf), 0));
    char *start = NULL, *str = NULL, *temp = NULL;
    start = buf;
    printf("\n Start Pointer Val = %ld", &start);
    while (start != NULL) {
        printf("\n While Loop");
        if (i + 2048 * sizeof(char) < numbytes) {
            printf("\n If 1");
            str = (char *)malloc(sizeof(char) * 2048);
            memcpy(str, start, sizeof(char) * 2048);
            i = i + 2048 * sizeof(char);
            buf_size = send(fd, str, 2048, 0);
            free(str);
            printf("\n Sent %d bytes total : %d", buf_size, total =
                   total + buf_size);

            temp = start + sizeof(char) * 2048;
            start = temp;

        } else {

            i = numbytes - i * sizeof(char);
            if (i > 0) {
                printf("\n If 2");
                printf("\n Value of i %d", i);
                str = (char *)malloc(sizeof(char) * i);
                memcpy(str, start, sizeof(char) * i);
                printf("Total bytes finally sent:%d", total =
                       total + send(fd, str, i, 0));
                if (total == numbytes) {
                    printf("\nTransfer Complete!");
                }
                free(str);

            }
            start = NULL;
        }
    }
    printf("out of loop!");
    return 0;
}

Answer 1

Try something like this (printf() statements omitted for clarity):

int send_buf(in fd, void *buf, int numbytes)
{
    char *start = (char*) buf;
    while (numbytes > 0)
    {
        int sent = send(fd, start, numbytes, 0);
        if (sent <= 0)
        {
            if ((sent == -1) && (errno == EAGAIN))
            {
                fd_set wfds;
                FD_ZERO(&wfds);
                FD_SET(fd, &wfds);
                if (select(fd + 1, NULL, &wfds, NULL, NULL) == 1)
                    continue;
            }
            return -1;
        }

        start += sent;
        numbytes -= sent;
    }

    return 0;
}

int return_result(int fd, char *content_type, void *buf, int numbytes) 
{ 
    char out_buf[BUF_SIZE], 

    int len = sprintf(out_buf,
        "HTTP/1.1 200 OK\r\n"
        "Content-Type: %s\r\n"
        "Content-Length: %d\r\n"
        "Connection: Close\r\n"
        "\r\n",
        content_type,
        numb); 

    if (send_buf(fd, out_buf, len) != 0)
        return -1;

    if (send_buf(fd, buf, numbytes) != 0)
        return -1;

    return 0; 
}