Send data to SED devices

Question

Hi, 
 I have a functioning CoAP client/server based OpenThread mesh network. My clients are SEDs. I can send data from clients to the CoAP server. Now I want to do the opposite, to send data from server to the SED clients. I have the unicast IPV6 of the SEDs on server side. I am thinking of using 'coap_send_request ()' as used by the clients to send data packet from server. I am not clear how on clients side to receive this. On server side I can see 'srv_context' and 'otCoapResource' structures and 'otCoapStart' used to manage data transmitted by the client. But I dont think I can start another CoAP server on client side, and there is no need for that. May be what we need is a kernel thread to look into packets being received and then set an kernel event or something like that to indicate data receive. What would be the best way of moving foward. 
 Cheers, 
 Kaushalya

kaushalyasat · Accepted Answer

Thanks Susheel, your help is much appreciated.

kaushalyasat · Answer

Hi Susheel, 
 Thanks. I think I managed to get it done. Still I dont know if the way I have done it is acceptable. So good to get some Thread expert run through this. 
 What I have done is in the host or coap server 
 static otCoapResource host_resource = {	
	.mUriPath = HOST_URI_PATH,
	.mHandler = NULL,
	.mContext = NULL,
	.mNext = NULL,
};

static const char *const host_option[] = {HOST_URI_PATH, NULL};

static void sensor_send_handler(void *context, otMessage *message, const otMessageInfo *message_info) {
..
}

int ot_coap_init (...) {

coap_init(AF_INET6, NULL);
 .
 .
 .
 srv_context.on_sensor_data_request = on_sensor_data_request;
 .
 srv_context.ot = openthread_get_default_instance();
 .
 host_resource.mContext = srv_context.ot;
	host_resource.mHandler = sensor_send_handler;
	.
	otCoapAddResource(srv_context.ot, &sensor_resource);
}

On coap client side 
 static otCoapResource host_resource = {
	.mUriPath = HOST_URI_PATH,
	.mHandler = NULL,
	.mContext = NULL,
	.mNext = NULL,
};

struct server_context {
	struct otInstance *ot;
	host_data_request_callback_t on_host_data_request;
};

static struct server_context srv_context = {
	.ot = NULL,
	.on_host_data_request = NULL
};

static void on_host_data_request (uint8_t host_msg_ID) {
	switch (host_msg_ID) {
	.
	.
	.
}

static void host_request_handler(void *context, otMessage *message, const otMessageInfo *message_info) {
	uint8_t buff[50];
	uint16_t msgLen=0;
	uint16_t byteCnt=0;

msgLen = otMessageGetLength (message)-otMessageGetOffset(message);
	byteCnt = otMessageRead(message, otMessageGetOffset(message), buff, msgLen);	
	LOG_INF ("Bytes Read %d", byteCnt);

srv_context.on_host_data_request (buff[1]);	// host message ID
}

static void coap_default_handler(void *context, otMessage *message, const otMessageInfo *message_info)
{
	ARG_UNUSED(context);
	ARG_UNUSED(message);
	ARG_UNUSED(message_info);

LOG_INF("Received CoAP message that does not match any request "
 "or resource");
}

void coap_client_utils_init (...) {
 .
 .
 .
 srv_context.on_host_data_request = on_host_data_request; 
 srv_context.ot = openthread_get_default_instance();
 
 host_resource.mContext = srv_context.ot;
	host_resource.mHandler = host_request_handler;
	
	otCoapSetDefaultHandler(srv_context.ot, coap_default_handler, NULL);
	otCoapAddResource(srv_context.ot, &host_resource);

err = otCoapStart(srv_context.ot, COAP_PORT);
	if (err != OT_ERROR_NONE) {
 LOG_ERR("Failed to start OT CoAP. Error: %d", err);
	}
 
} 
 Basically I have done what the coap client has done on its side on coap server on initialization. I had to increase stack size for system workqueue to 2048 in prj.conf (may be this can be lowered but I havent tested it). 
 Is this method acceptable? 
 
 Cheers, 
 Kaushalya

Send data to SED devices

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