nRF9151: fcntl() errno 9 EBADF

RE: nRF9151: fcntl() errno 9 EBADF

Hakon — Tue, 09 Dec 2025 07:40:11 GMT

Using fcntl() instead of nrf_fcntl() seems to work for me. This kinda makes sense since you are using the Zephyr socket API when creating the socket, but you are calling nrf_fcntl() which is the modem lib API. I think you should stick to one API when dealing with sockets.

Edit; Never mind, it works with the Zephyr stack, but not with the offloaded sockets.

Edit2; This works for me;

#include <stdio.h>
#include <ncs_version.h>
#include <zephyr/kernel.h>
#include <zephyr/net/socket.h>
#include <zephyr/logging/log.h>
#include <fcntl.h>

#include <nrf_socket.h>
#include <modem/nrf_modem_lib.h>
#include <modem/lte_lc.h>

int main(void) {
    int fd;
    int err;
    printk("Starting fcntl test\n");
    
    err = nrf_modem_lib_init();
    fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    /* fd >= 0 */

    int rai = RAI_ONGOING;
    err = setsockopt(fd, SOL_SOCKET, SO_RAI, &rai, sizeof(rai));
    /* err == 0 */

    err = fcntl(fd, NRF_F_SETFL, NRF_O_NONBLOCK);
    /* err == -1 && errno == 9 */
    printk("%d\n", err);
    printk("%d\n", errno);
    return 0;
}

RE: nRF9151: fcntl() errno 9 EBADF

klaasg — Fri, 05 Dec 2025 12:53:59 GMT

We use SDK v2.7.0 (working on moving up), modem firmware 2.0.2 on nRF9151.

It's really this simple piece of code:

fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
/* fd >= 0 */

int rai = RAI_ONGOING;
err = setsockopt(fd, SOL_SOCKET, SO_RAI, &rai, sizeof(rai));
/* err == 0 */

nrf_fcntl(fd, NRF_F_SETFL, NRF_O_NONBLOCK);
/* err == -1 && errno == 9 */

While Registered and RRC Connected on an NB-IoT network (example 20620), sometimes nrf_fcntl returns this.

The response is immediate (<1ms).

In what case does fcntl set errno to EBADF?

RE: nRF9151: fcntl() errno 9 EBADF

Hakon — Thu, 04 Dec 2025 13:18:03 GMT

Hello,

can you provide more information? What SDK, modem firmware, and hardware are you using? Any logs?