TCP IPv6 connection fails with Zephyr BSD sockets (errno 116) on nRF54L15 Thread CLI, while OpenThread TCP works

RE: TCP IPv6 connection fails with Zephyr BSD sockets (errno 116) on nRF54L15 Thread CLI, while OpenThread TCP works

Marte Myrvold — Tue, 20 Jan 2026 10:41:02 GMT

Hi,

Can you share what you have in your prj.conf?

There are some socket samples in Zephyr that use BSD sockets, such as the Echo server and Echo client. These can be built with OpenThread overlays (overlay-ot.conf), so I recommend looking at them. Please note that TCP is disabled in the OpenThread overlays in these samples to avoid heavy traffic, but it should still be possible to use TCP by leaving it enabled.

Best regards,
Marte

RE: TCP IPv6 connection fails with Zephyr BSD sockets (errno 116) on nRF54L15 Thread CLI, while OpenThread TCP works

rezwin — Mon, 19 Jan 2026 04:57:54 GMT

Thank you for the suggestion.

I have already verified that the OpenThread native TCP API (as seen in cli_tcp.cpp) works correctly. I am able to establish a connection and send data using the otTcp CLI commands.

However, my project requirements specifically require the use of the Standard BSD Socket API (socket(), connect(), send()) rather than the native OpenThread calls. Currently, when I attempt to use BSD sockets over the Thread interface, I am encountering errors (specifically 116 ) that do not occur when using the CLI.

Could you please help me identify if there are specific Kconfig requirements or buffer configurations needed in Zephyr to properly bridge the BSD socket layer to the OpenThread TCP stack?

RE: TCP IPv6 connection fails with Zephyr BSD sockets (errno 116) on nRF54L15 Thread CLI, while OpenThread TCP works

Marte Myrvold — Fri, 16 Jan 2026 12:58:50 GMT

Hi,

Have you tried using the socket functions used by the OpenThread CLI commands? You can find them in modules/lib/openthread/src/cli/cli_tcp.cpp,

Best regards,
Marte

RE: TCP IPv6 connection fails with Zephyr BSD sockets (errno 116) on nRF54L15 Thread CLI, while OpenThread TCP works

rezwin — Thu, 15 Jan 2026 16:09:30 GMT

I have already enabled these configs and still the problem exists.

RE: TCP IPv6 connection fails with Zephyr BSD sockets (errno 116) on nRF54L15 Thread CLI, while OpenThread TCP works

Marte Myrvold — Thu, 15 Jan 2026 15:58:50 GMT

Hi,

You can use UDP and TCP via the BSD sockets if you use Zepyr's OpenThread integration and IP stack. To use Zephyr's stack and BSD sockets, make sure that these configs are enabled:

CONFIG_NETWORKING=y
CONFIG_NET_L2_OPENTHREAD=y
CONFIG_NET_SOCKETS=y

Please note that nRF Connect SDK 3.1.0 the OpenThread samples were changed: by default they now use the architecture where Zephyr networking is disabled and the OpenThread stack is used directly with the 802.15.4 driver, meaning Zephyr’s networking features (including BSD sockets) are not available unless you explicitly re‑enable them, see Migration guide 3.1.

Best regards,
Marte