failure to open TCP socket when using SSL with SARA-410M

[gasagna]

[x] I have read the Troubleshooting section of the ReadMe

What type of issues is this?

[ ] Request to support a new module [ ] Bug or problem compiling the library [x] Bug or issue with library functionality (ie, sending data over TCP/IP) [ ] Question or request for help

What are you working with?

Modem: SARA-R410M-02B-00 Main processor board: MKR NB 1500 TinyGSM version: 0.11.3 Code: Here is the relevant code I am using. Read below for further info on the background

// enable http logging
#define LOGGING

// dump commands to serial port
#define DUMP_AT_COMMANDS true

// define sim module
#define TINY_GSM_MODEM_SARAR4

// Your GPRS credentials, if any
const char apn[]      = "em";
const char gprsUser[] = "";
const char gprsPass[] = "";

// import libraries
#include <ArduinoHttpClient.h>
#include <ArduinoLowPower.h>
#include <StreamDebugger.h>
#include <TinyGsmClient.h>
#include <MKRNB.h>

// influxdb parameters
#define INFLUXDB_TOKEN "Token ** YOU WILL NEED YOUR OWN TOKEN **"
#define INFLUXDB_ADDR  "europe-west1-1.gcp.cloud2.influxdata.com"
#define INFLUXDB_PORT 443
#define INFLUXDB_BUCKET "your-own-bucket"
#define INFLUXDB_ORG "your-own-org"

// send message to the cloud
int sendSample(const String& message, HttpClient& httpclient) {
    // create request string
    String request = "/api/v2/write?bucket=";
    request += INFLUXDB_BUCKET;
    request += "&org=" ;
    request += INFLUXDB_ORG ;
    request += "&precision=s";

    // send request
    httpclient.beginRequest();
    int httpCode = httpclient.post(request);
    httpclient.sendHeader("Authorization", INFLUXDB_TOKEN);
    httpclient.sendHeader("Content-Type", "text/plain; charset=utf-8");
    httpclient.sendHeader("Content-Length", message.length());
    httpclient.sendHeader("Accept", "application/json");
    httpclient.beginBody();
    httpclient.print(message);
    httpclient.endRequest();

    // read status code
    return httpclient.responseStatusCode();
}


/****************************************************/
/*    Global variables                              */
/****************************************************/

// tools to attach to the cellular network
#if DUMP_AT_COMMANDS
    StreamDebugger debugger(Serial2, Serial);
    TinyGsm        modem(debugger);
#else
    TinyGsm        modem(Serial2);
#endif

// gsm client
TinyGsmClientSecure client(modem);

// initialize the clients
HttpClient httpclient = HttpClient(client, INFLUXDB_ADDR, INFLUXDB_PORT);

// example data to be sent
String line = "test message";

/****************************************************/
/*    Main functions                                */
/****************************************************/
// setup function
void setup() {
    // initialize serial communications for monitoring via usb
    Serial.begin(115200);
    while (!Serial) {}

    // initialise connection with module SARA
    Serial2.begin(115200);
    while (!Serial2) {}

    Serial.print("Connecting to cellular network ... ");
    modem.restart();
    Serial.println("done");
    String modemInfo = modem.getModemInfo();
    Serial.print("Modem Info: ");
    Serial.println(modemInfo);
}

// loop function
void loop() {
    // begin loop
    Serial.println();

    Serial.print("Waiting for network ...");
    if (!modem.waitForNetwork()) {
        Serial.println(" fail");
        delay(10000);
        return;
    }
    Serial.println(" success");

    if (modem.isNetworkConnected()) { Serial.println("Network connected"); }

    // GPRS connection parameters are usually set after network registration
    Serial.print(F("Connecting to "));
    Serial.print(apn);
    Serial.print(" ... ");
    if (!modem.gprsConnect(apn, gprsUser, gprsPass)) {
        Serial.println(" fail");
        delay(10000);
        return;
    }
    Serial.println(" success");

    if (modem.isGprsConnected()) { Serial.println("GPRS connected"); }

    // Currently, this is needed for HTTPS (see TinyGSM lib examples)
    httpclient.connectionKeepAlive();  

    // send message
    Serial.println("Starting request ...");
    int httpResponseCode = sendSample(line, httpclient);

    // if all good
    if (httpCode == HTTP_SUCCESS) {
        Serial.println(" Sending POST request");
        if (httpResponseCode == 204) {
            Serial.println("  Sample sent correctly, got 204");
        } else {
            Serial.print("  Sample not sent, got  ");
            Serial.println(httpResponseCode); 
            Serial.print(" ");
            Serial.print(httpResponse);
        }
    } else { 
        Serial.print(" Post request not sent, got ");
        Serial.println(httpCode);
    }

    // disconnect
    modem.gprsDisconnect();
    Serial.println(F("GPRS disconnected"));

    // wait till next time
    LowPower.sleep(SAMPLING_TIME);
}

Scenario, steps to reproduce (with AT command log)

I am using the TinyGSM and ArduinoHTTPClient libraries to post data to my InfluxDB cloud account via SSL. The server is managed by google cloud and is located at "europe-west1-1.gcp.cloud2.influxdata.com", as described in the official InfluxDB docs. As can be seen from the code above, I am trying to open a secure connection at port 443. This does not seem to work, and here is the relevant excerpt from the AT command dump.

20:31:18.363 -> AT+USOCR=6
20:31:18.363 -> 
20:31:18.363 -> +USOCR: 0
20:31:18.363 -> 
20:31:18.363 -> OK
20:31:18.363 -> AT+USOSEC=0,1
20:31:18.396 -> 
20:31:18.396 -> OK
20:31:18.396 -> AT+USOCO=0,"europe-west1-1.gcp.cloud2.influxdata.com",443,1
20:31:18.396 -> 
20:31:18.396 -> OK
20:31:20.783 -> 
20:31:20.783 -> +UUSOCO: 0,255

The return code from the AT+USOCO command is +UUSOCO: 0,255. From the modem's docs this return code is not documented, so I am at a loss here, and can't proceed.

I have tried posting data on an private InfluxDB instance managed on my own server that does not use SSL (using a TinyGsmClient object), and I can successfully post data.

[gasagna]

This does not appear to be an issue with the InfluxDB website or my own code, but rather a general issue with some https websites and my gsm modem. I have also tried the HttpsClient example provided by this library, using other websites (e.g. discourse.julialang.org), and the same +UUSOCO: 0,255 code is returned.