mqtts reported an error when creating a socket: Operation not supported on socket.

Question

I want nRF9160 to do mqtts connection without certificate.

Modem FW:1.2.3

Here is my mqtt client_init:

static int client_init(struct mqtt_client *client)
{
	int err;

	mqtt_client_init(client);

	err = broker_init();
	if (err) {
		LOG_ERR("Failed to initialize broker connection");
		return err;
	}

	/* MQTT client configuration */
	client->broker = &broker;
	client->evt_cb = mqtt_evt_handler;
	client->client_id.utf8 = (uint8_t *)CONFIG_MQTT_CLIENT_ID;
	client->client_id.size = strlen(CONFIG_MQTT_CLIENT_ID);
	client->password = NULL;
	client->user_name = NULL;
	client->protocol_version = MQTT_VERSION_3_1_1;

	/* MQTT buffers configuration */
	client->rx_buf = rx_buffer;
	client->rx_buf_size = sizeof(rx_buffer);
	client->tx_buf = tx_buffer;
	client->tx_buf_size = sizeof(tx_buffer);

	/* MQTT transport configuration */
	struct mqtt_sec_config *tls_cfg = &(client->transport).tls.config;
	static sec_tag_t sec_tag_list[] = { CONFIG_MQTT_TLS_SEC_TAG };

	LOG_INF("TLS enabled");
	client->transport.type = MQTT_TRANSPORT_SECURE;

	tls_cfg->peer_verify = TLS_PEER_VERIFY_NONE;
	tls_cfg->cipher_count = 0;
	tls_cfg->cipher_list = NULL;
	tls_cfg->sec_tag_count = 0;
	tls_cfg->sec_tag_list = NULL;
	tls_cfg->hostname = CONFIG_MQTT_BROKER_HOSTNAME;

	tls_cfg->session_cache = IS_ENABLED(CONFIG_MQTT_TLS_SESSION_CACHING) ?
					    TLS_SESSION_CACHE_ENABLED :
					    TLS_SESSION_CACHE_DISABLED;

	return err;
}

When I use 9160DK, mqtts is connected normally. But when using the 9160 chip, there is an error in the connection. Here is my log:

[00:00:00.243,316] [0m<inf> main: Connecting to LTE network.[0m
[00:00:00.243,316] [0m<inf> main: This may take several minutes.[0m
[00:00:00.243,377] [0m<inf> flash_control: No apn found, use default apn[0m
[00:00:00.249,908] [0m<inf> main: Set to the default APN CMNBIOT2.[0m
[00:00:00.258,087] [0m<inf> lte_lc: Using legacy LTE PCO mode...[0m
[00:00:02.258,117] [0m<inf> main: CSCON : 1[0m
[18:48:50.833]收←◆[00:00:04.283,386] [0m<inf> main: Connected to LTE network.[0m

[00:00:04.286,163] [0m<inf> mqtt_engine: IPv4 Address found 47.106.164.80[0m
[00:00:04.286,193] [0m<inf> mqtt_engine: TLS enabled[0m
[00:00:04.286,468] [0m<dbg> net_mqtt_sock_tls.mqtt_client_tls_connect: (0x20015220): Created socket 1[0m
[00:00:04.660,552] [1;31m<err> mqtt_engine: mqtt_connect -45[0m
[00:00:04.660,583] [1;31m<err> mqtt_engine: ERROR: mqtt_disconnect -57[0m

-45 is EOPNOTSUPP, and typically indicates that you have written wrong certificates to the device. But I had peer_verify set to 0. Why is there a -45 error?

Heidi · Accepted Answer

Hi! 
 
 From the modem trace and the return of %CMNG it looks like there is a Root CA stored in sec_tag 24 and sec_tag 16842753 but the TLS connection is trying to be establishing using sec_tag 1, where there is no root certificate. 
 
 Try using the correct sec_tag in your application, and the modem should be able to find the root certificate. 
 
 Best regards, 
 Heidi

Heidi · Answer

The modem trace from the custom board. 
 
 Your certificates aren't stored with the correct type. The root CA needs to be stored as type 0. Right now, a client certificate is stored as a root CA which is why the TLS connection is failing.

mqtts reported an error when creating a socket: Operation not supported on socket.

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