Arduino MKR GSM 1400 SSL client example fails to connect

Question

I am using the GsmSSLWebClient example which comes with the MKRGSM library. The original example works just fine, I get the arduino ascii logo. But when I change the URL the arduino doesn't get any answer:

//char server[] = "arduino.cc"; 
//char path[] = "/asciilogo.txt";
char server[] = "wepardi.fi"; 
char path[] = "/robots.txt";
Starting Arduino web client.
connecting...
connected
GET /robots.txt HTTP/1.1
Host: wepardi.fi
Connection: close
disconnecting.

From Firefox https://www.wepardi.fi/robots.txt is displayed correctly. I tried also some other sites, and from some of them I get the ascii file content correctly, and from some others not.

Something wrong with my settings?

Prints from debug mode:

connecting...

...

AT+USECMNG=0,0,"VeriSign_Class_3_Public_Primary_Certification_Authority_G5",1239
>
+USECMNG: 0,0,"VeriSign_Class_3_Public_Primary_Certification_Authority_G5","cb17e431673ee209fe455793f30afa1c"
OK
AT+USOCR=6
+USOCR: 0
OK
AT+USOSEC=0,1,0
OK
AT+USECPRF=0,0,1,4,"www.wepardi.fi"
OK
AT+USOCO=0,"www.wepardi.fi",443
ERROR
+UUSOCL: 0
AT+USOCL=0
ERROR
connected
GET /robots.txt HTTP/1.1
Host: www.wepardi.fi
Connection: close
disconnecting.

Command AT+USOCO=0,"www.wepardi.fi",443 fails

GsmWebClient (no SSL) example works fine with any hosts I have tried.

• Juraj: in browser you enter www.wepardi.fi and in arduino only wepardi.fi

Answer 1

I finally found a solution to this problem. Disabling certificate validation in MKRGSM library makes the SSL connection succeed also to this site. In MKRGSM/src/GSMClient.cpp I changed

// MODEM.sendf("AT+USECPRF=0,0,1,4,\"%s\"", _host);
 MODEM.sendf("AT+USECPRF=0");

to use modem factory settings. I still don't know what was the problem with the certificates. Thanks to everyone who tried to help with this.

Answer 2

The problem you have is that of redirection.

You connect to wepardi.fi and request the file /robots.txt from that host. It immediately tells you "Ok, but that file is actually on www.wepardi.fi/robots.txt. Go get it from there.

But it won't.

You have to go direct to the source.

Here's a trace:

GET /robots.txt HTTP/1.1
Host: wepardi.fi
Connection: close
HTTP/1.1 302 Found
Date: 2019年1月08日 14:26:51 GMT
Server: Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips PHP/7.0.32
Strict-Transport-Security: max-age=63072000; includeSubdomains;
X-Powered-By: PHP/7.0.32
Location: https://www.wepardi.fi/
Cache-Control: max-age=1296000
Expires: 2019年1月23日 14:26:51 GMT
Content-Length: 0
Connection: close
Content-Type: text/html; charset=UTF-8

And when you change to www.wepardi.fi:

GET /robots.txt HTTP/1.1
Host: www.wepardi.fi
Connection: close
HTTP/1.1 200 OK
Date: 2019年1月08日 14:27:49 GMT
Server: Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips PHP/7.0.32
Strict-Transport-Security: max-age=63072000; includeSubdomains;
X-Powered-By: PHP/7.0.32
X-Robots-Tag: noindex, follow
Link: <https://www.wepardi.fi/wp-json/>; rel="https://api.w.org/"
Cache-Control: max-age=300
Expires: 2019年1月08日 14:32:49 GMT
Content-Length: 67
Connection: close
Content-Type: text/plain; charset=utf-8
User-agent: *
Disallow: /wp-admin/
Allow: /wp-admin/admin-ajax.php
read:errno=0

• Tiina: Thanks, but still I don't get the file content: Starting Arduino web client. connecting... connected GET /robots.txt HTTP/1.1 Host: www.wepardi.fi Connection: close disconnecting.
• Majenko: Can you get any sort of feedback to the request?