How to set a udp socket peer connect timeout?

RE: How to set a udp socket peer connect timeout?

Ron Segal — Tue, 20 Sep 2022 19:58:53 GMT

Hi Sigurd

Yes, bearing in mind that this is a dtls link (as mentioned above, although the question should probably have been titled that), connect (zsock_connect) is blocking. This is clear because the print diagnostics in the code above is never reached until the call eventually times out.

However, by implementing the SO_SNDTIMEO socket option that you mentioned, the dtls connect is now timing out at the set number of seconds. Here's code that works:

	struct timeval timeo = {
		.tv_sec = 5,
		.tv_usec = 0,
	};

	err = setsockopt(client_fd, SOL_SOCKET, SO_SNDTIMEO, &timeo, sizeof(timeo));
	if (err) {
		DBG_PRINTF("Failed to set socket timeout, errno %d", errno);
		err = -errno;
		goto error;
	}

	DBG_PRINTF("Trying to connect to: ");
#ifdef CONFIG_PRINT_DBG
	printhex(host_addr.data,sizeof(host_addr.data));
#endif
	DBG_PRINTF("\r\n");

	//** zsock_connect - connect socket to dtls peer - our udp2mqtt gateway
	//** https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.0.0/zephyr/connectivity/networking/api/sockets.html
	err = connect(client_fd, (struct sockaddr *)&host_addr, sizeof(struct sockaddr_in));
	if (err < 0) {
		printk("Connect failed : %d\n", errno);
		goto error;
	}
	else {
		DBG_PRINTF("Server Connected\r\n");
	}

	return 0;

So problem solved. Thanks for your help in putting me on the right track.

Cheers, Ron

RE: How to set a udp socket peer connect timeout?

Sigurd Hellesvik — Tue, 20 Sep 2022 13:09:15 GMT

After looking around myself for another setting or socket option, I asked our developers.

Here is what they say:

"No connection is established for connection-less sockets upon connect(). That will only set the peer address. Therefore connect() on a UDP socket is always a blocking operation. We do support timeouts on connect() for TCP sockets via SO_SNDTIMEO"

EDIT: Are you certain that it is connect() that is blocking, and not for example send()?

Regards,
Sigurd Hellesvik

RE: How to set a udp socket peer connect timeout?

Ron Segal — Tue, 20 Sep 2022 07:44:01 GMT

Hi Sigurd,

Thanks. I had already tried NET_SOCKETS_CONNECT_TIMEOUT in prj.conf but it doesn't seem to do anything. The socket still hangs for a long timeout if there is no response from the other end. Unlike CONFIG_LTE_NETWORK_TIMEOUT which does timeout the LTE/NB-IoT connection. Any other ideas. Perhaps the code that is supposed to use that net sockets timeout configuration value can itself be modified?

RE: How to set a udp socket peer connect timeout?

Sigurd Hellesvik — Tue, 20 Sep 2022 07:27:19 GMT

Hi Ron,

I have not tried it myself, but I think you are looking for the NET_SOCKETS_CONNECT_TIMEOUT configuration option.

Is this what you needed?

(It does not appear in our Kconfig search for some reason. I will ask our documentation team about this.)
EDIT: nvm, I found it at https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.1.0/kconfig/index.html#CONFIG_NET_SOCKETS_CONNECT_TIMEOUT

Regards,
Sigurd Hellesvik

RE: How to set a udp socket peer connect timeout?

Ron Segal — Tue, 20 Sep 2022 04:59:21 GMT

Thank you Sigurd.

There is a dtls to mqtt gateway at the other end of the link, which is also communicating over NB-IoT. If the gateway isn't working properly or is unreachable for some reason, the client needs to timeout quickly to avoid unnecessary current draw from the battery before trying again. So far I haven't been able to find a reasonably straightforward way to either timeout or gracefully abort the socket.

RE: How to set a udp socket peer connect timeout?

Sigurd Hellesvik — Mon, 19 Sep 2022 13:57:26 GMT

Hi Ron,

I will look into your case and return with more information tomorrow.

Regards,
Sigurd Hellesvik