Listing 1. nonblock.c

/* set socket non blocking */
fl = fcntl(accsock, F_GETFL);
fcntl(accsock, F_SETFL, fl | O_NONBLOCK);


void
poll_wait(int fd, int events)
{
    int n;
    struct pollfd pollfds[1];
    memset((char *) &pollfds, 0, sizeof(pollfds));

    pollfds[0].fd = fd;
    pollfds[0].events = events;

    n = poll(pollfds, 1, -1);
    if (n < 0) {
        perror("poll()");
        errx(1, "Poll failed");
    }
}

size_t
readmore(int sock, char *buf, size_t n) {

        fd_set rfds;
        int ret, bytes;



        poll_wait(sock,POLLERR | POLLIN );
        bytes = readall(sock, buf, n);

        if (0 == bytes) {
                perror("Connection closed");
                errx(1, "Readmore Connection closure");
                /* NOT REACHED */
        }

        return bytes;
}

size_t
readall(int sock, char *buf, size_t n) {
        size_t pos = 0;
        ssize_t res;

        while (n > pos) {
                res = read (sock, buf + pos, n - pos);
                switch ((int)res) {
                        case -1:
                                if (errno == EINTR || errno == EAGAIN)
                                        continue;
                                return 0;
                        case 0:
                                errno = EPIPE;
                                return pos;
                        default:
                                pos += (size_t)res;
                }
        }
        return (pos);
}


size_t
writenw(int fd, char *buf, size_t n)
{
        size_t pos = 0;
        ssize_t res;
        while (n > pos) {
                poll_wait(fd, POLLOUT | POLLERR);
                res = write (fd, buf + pos, n - pos);
                switch ((int)res) {
                        case -1:
                                if (errno == EINTR || errno == EAGAIN)
                                        continue;
                                return 0;
                        case 0:
                                errno = EPIPE;
                                return pos;
                        default:
                                pos += (size_t)res;
                }
        }
        return (pos);

}