Question about survey recv timeout

[zlkang]

void server(const char *url)
{
nng_socket sock;
int rv;

if ((rv = nng_surveyor0_open(&sock)) != 0)
{
    fatal("nng_surveyor0_open", rv);
}

if ((rv = nng_listen(sock, url, NULL, 0)) != 0)
{
    fatal("nng_listen", rv);
}

nng_socket_set_ms(sock, NNG_OPT_RECVTIMEO, 3000);

for (;;)
{
    printf("SERVER: SENDING DATE SURVEY REQUEST\n");
    char date_str[] = "DATE";
    if ((rv = nng_send(sock, date_str, strlen(date_str) + 1, 0)) != 0)
    {
        fatal("nng_send", rv);
    }

    for (;;)
    {
        char *buf = NULL;
        size_t sz;

        rv = nng_recv(sock, &buf, &sz, NNG_FLAG_ALLOC);
        if (rv == NNG_ETIMEDOUT)
        {
            break;
        }

        if (rv != 0)
        {
            fatal("nng_recv", rv);
        }
        printf("SERVER: RECEIVED \"%s\" SURVEY RESPONSE\n", buf);
        nng_free(buf, sz);
    }

    printf("SERVER: SURVEY COMPLETE\n");
}

}

I encountered a problem. On the survey server, I want to change the timeout of nng_recv. When using nng_socket_set_ms(sock, NNG_OPT_RECVTIMEO, timeout), if the timeout is less than 1 second, nng_recv will successfully block the corresponding time. But when the timeout is greater than 1 second, nng_recv is always blocked for 1 second.