LTE_M reconnect

[Hoang]

Dear, 

I am using THINGY91 for proving my concept, I put THINGY91 in the freezer - to adapt to the temperature. 

I am using NB_iot of telia (norway)

My problem is: sometimes my thingy91 lost the network (the freezer is so good :( ),  and couldn't send the data to my webserver

I tried to change my state-machine: THINGY91 will check the network and reconnect if it couldn't find the network 

1. check the network:

/****************************************************************************************************
*name:  NETWORK CHECK
*todo:  find status of the network
*return: connect/disconnect: *mccmnc
  * 
****************************************************************************************************/
void NETW_CHECK(char *mccmnc )
 {
	const char *ATCOPS="AT+COPS?"; 
        
        
        int at_socket_fd = socket(AF_LTE, 0, NPROTO_AT);
       // printk("LTE socket is: %d \n",at_socket_fd); 
	
	if (at_socket_fd < 0) {
		printk("Socket err: %d, errno: %d\r\n", at_socket_fd, errno);
	}
	/*
        * find MNC and MCC
        */
        int bytes_written0 = send(at_socket_fd, ATCOPS, strlen(ATCOPS), 0);
	if (bytes_written0 > 0) {
			int r_bytes =
				blocking_recv(at_socket_fd, recv_buf,
					      sizeof(recv_buf), MSG_DONTWAIT);
			if (r_bytes > 0) {
				//printk("%s", recv_buf);
                                char splitStringsmcc[10][10]; 
                                 split_string_ltepos(recv_buf,splitStringsmcc);
                                 memcpy(mccmnc,splitStringsmcc[1],sizeof(splitStringsmcc[1]));
                                
                                  printk("MCC&MNC: %s\n\r",mccmnc);
			              }
		
	}
       
        (void)close(at_socket_fd);
         
}

I will return MCCMNC,"24202" for telia, and if it couldnt find the network, I will try to reconnect: 

void reconnect_nw(void){
                
                int err;
		printk("ReConnecting to LTE network. ");
		printk("This may take several minutes.\n");
		//ui_led_set_pattern(UI_LTE_CONNECTING);

		err = lte_lc_init_and_connect();
		if (err) {
			printk("LTE link could not be established.\n");
			
		}

		printk("Connected to LTE network\n");
}  

But, this function lte_lc_init_and_connect()  didnt work, it just returned "LTE link could not be established.;

I am using the config file as the same with : master/applications/asset_tracker/prj_nrf9160_pca20035ns.conf, it will contain "CONFIG_LTE_AUTO_INIT_AND_CONNECT=n"

Could you plz help me, I need a solution how can thingy91 can automatically re-connect the network if the network is disconnected. 

Thanks so much 

Best Regards, 

Hoang Nguyen

[Didrik Rokhaug]

Hi.

The modem will automatically try to reconnect to the network, so there is no action necessary from the application.

However, if the signal in the freezer is so bad that you lose connection, it is probably not strong enough for the device to be able to reconnect while inside the freezer.

Best regards,

Didrik

[Hoang]

Hi Didrik Rokhaug, 

I tried to simulate the situation: I used aluminum paper to cover the THINGY:91, and put them in 1 metal box, and connect to my computer to adapt the output report.

I am using NB_ioT (Telia) 

 I got the problem in http_post: 

bool myhttp_post (char *PostString, char *HTTP_HOST, int HTTP_PORT)
{
     
   bool poststat = false;
   struct sockaddr_in local_addr;
   struct addrinfo *res;
   printk("Webserver: http://%s:%d \n\r",HTTP_HOST,HTTP_PORT); 

   local_addr.sin_family = AF_INET;
   local_addr.sin_port = htons(0);
   local_addr.sin_addr.s_addr = 0;
 
    int err = getaddrinfo(HTTP_HOST, NULL, NULL, &res);
    printk("get addrinfo\n\r");
    printk("getaddrinfo err: %d\n\r", err);
    ((struct sockaddr_in *)res->ai_addr)->sin_port = htons(HTTP_PORT);
    
   
    char send_buf[MAXLINE + 1];
    int send_data_len_post  = snprintk(send_buf,
				         500, 
				         POST_TEMPLATE, HTTP_PATH,
				         HTTP_HOST, strlen(PostString),
				         PostString);

    // printf("send_buf is: %s \n",send_buf);
    // printk("send err: %d\n\r", send_data_len_post);
     
     int client_fd = socket(AF_INET, SOCK_STREAM, 0);

     printk("client_fd: %d\n\r", client_fd);
     err = bind(client_fd, (struct sockaddr *)&local_addr, sizeof(local_addr));
     printk("bind err: %d\n\r", err);
     err = blocking_connect(client_fd, (struct sockaddr *)res->ai_addr,sizeof(struct sockaddr_in));
     printk("connect err: %d\n\r", err);

     int num_bytes = send(client_fd, send_buf, send_data_len_post, 0);
    
     printk("send err: %d\n\r", num_bytes);
     
     
     printk("Close socket \n\r");
     err = close(client_fd);
     
     freeaddrinfo(res);
     printk("============================== DONE SENDING =============================================== \n\r");
     poststat = true; 
     return poststat; 
     
     /*
     problem: take so long time to send()
     */
        
}

when the signal is bad (put the device in the metal box with aluminum paper cover around) 

get addrinfo

getaddrinfo err: 0

client_fd: 3

bind err: 0

It stuck here 

................

Case1: If I tried to take the device out early ( < 30s ) - the network is backed early

It could work: 

connect err: 0

send err: 495

Close socket 

============================== DONE SENDING =============================================== 

 

Case 2: Keep the device in the box 

It will return error after 30-40s:

connect err: -1

send err: -1

Close socket 

// couldnt send

Case3:  If I tried to take the device out late( 1mn after that ) - the network is backed 

Nothing comes, it just stuck here forever:

get addrinfo

getaddrinfo err: 0

client_fd: 3

bind err: 0

..................... the device stopped sending data and stuck here ( took the device out of the box, took away the aluminum paper) 

I checked the code: I stuck at this step: 

err = blocking_connect(client_fd, (struct sockaddr *)res->ai_addr,sizeof(struct sockaddr_in));

and blocking_connect():

int blocking_connect(int fd, struct sockaddr *local_addr, socklen_t len)
{
	int err;

	do {
		err = connect(fd, local_addr, len);
	} while (err < 0 && errno == EAGAIN);

	return err;
}

It stuck in the loop: do{}while() forever? without the timeout?

Do you have any suggestions to fix it? 

Thanks so much 

Hoang Nguyen

[Hoang]

I am using httpPost from: https://github.com/Rallare/fw-nrfconnect-nrf/blob/nrf9160_samples/samples/nrf9160/http/src/main.c

[Didrik Rokhaug]

I am a bit confused about the difference between cases 2 and 3.

Do you take the device out of the box later in case 3 than 2?

If so, why would you get a different result from case 2?

Connect and send returns their error values in the errno variable. Can you print that value as well?

Also, a modem trace in case 3 would be helpful.