SIM900 TCP Connection issue

Question

I am having a strange issue where if I try and create a TCP connection to my service, it doesn't work. But any other website, such as google, works fine. The serial monitor output is also slightly different, but I cannot see any difference in the code. I am using this module for communications.

This is the method that I am using:

void SendPost()
{
  Serial1.println("AT+CGATT?");
  delay(1000); 
  ShowSerialData();

  Serial1.println("AT+CSTT=\"everywhere\"");//start task and setting the APN,
  delay(1000); 
  ShowSerialData();

  Serial1.println("AT+CIICR");//bring up wireless connection
  delay(3000); 
  ShowSerialData();

  Serial1.println("AT+CIFSR");//get local IP adress
  delay(2000); 
  ShowSerialData();

  Serial1.println("AT+CIPSPRT=0");
  delay(3000); 
  ShowSerialData();

  Serial1.println("AT+CIPSTART=\"tcp\",\"www.google.com/\",\"80\"");//start up the connection //https://rocky-garden-56471.herokuapp.com/breadcrum/lifecycle/register
  delay(5000); 
  ShowSerialData();

  Serial1.println("AT+CIPSEND");//begin send data to remote server
  delay(4000);
  ShowSerialData();
  
  Serial1.println("{\"device_info\":\"breadcrum-prototype-a\"}");  
  delay(500);
  ShowSerialData();

  Serial1.println((char)26);//sending
  delay(5000);//waitting for reply, important! the time is base on the condition of internet 
  
  Serial1.println(); 
  ShowSerialData();

  Serial1.println("AT+CIPCLOSE");//close the connection
  delay(100);
  ShowSerialData();
}

Using 'www.google.com' I get an OK upon tcp connection (with an expected error on the data as I try to POST):

Setup CompleteAT+CGATT?

+CGATT: 1

OK
AT+CSTT="everywhere"

OK
AT+CIICR

OK
AT+CIFSR

100.66.4.95
AT+CIPSPRT=0

OK
AT+CIPSTART="tcp","www.google.com/","80"

OK

STATE: IP STAAT+CIPSEND

ERROR
{"device_info":"breadcrum-prototype-a"}


AT+CIPCLOSE

ERROR

But using the address I actually want to post data to (https://rocky-garden-56471.herokuapp.com/breadcrum/lifecycle/register), it cannot connect and I get this:

Setup CompleteAT+CGATT?

+CGATT: 1

OK
AT+CSTT="everywhere"

OK
AT+CIICR

OK
AT+CIFSR

100.66.4.95
AT+CIPSPRT=0

OK
AT+CIPSTART="tcp","https://rocky-garden-56471.herokuapp.com/breAT+CIPSEND

ERROR
{"device_info":"breadcrum-prototype-a"}


AT+CIPCLOSE

ERROR

This errors on connection, and you can also see that the full address isn't printed out for some reason. Does anyone have any idea what could be causing this issue?

Thanks :)

EDIT: @Majenko, my previous version did what I believe you are describing. The issue being I got an error that I struggled to resolve so attempted this version. The previous version is:

void SubmitHttpRequest()
{
  Serial1.println("AT+CSQ");
  delay(100); 
  ShowSerialData();

  Serial1.println("AT+CGATT?");
  delay(100); 
  ShowSerialData();

  Serial1.println("AT+SAPBR=3,1,\"CONTYPE\",\"GPRS\"");//setting the SAPBR, the connection type is using gprs
  delay(1000); 
  ShowSerialData();

  Serial1.println("AT+SAPBR=3,1,\"APN\",\"everywhere\"");//setting the APN, the second need you fill in your local apn server
  delay(4000); 
  ShowSerialData();

 //Enable GPRS
  Serial1.println("AT+SAPBR=1,1");
  delay(2000); 
  ShowSerialData();

  //Query if connection is setup correctly, return IP address if it is 
  Serial1.println("AT+SAPBR=2,1");
  delay(2000); 
  ShowSerialData();

  Serial1.println("AT+HTTPINIT"); //init the HTTP request 
  delay(2000); 
  ShowSerialData();

//Set up bearer profile identifier (NEW PART)
  Serial1.println("AT+HTTPPARA=\"CID\",1");
  delay(2000); 
  ShowSerialData();


  Serial1.println("AT+HTTPPARA=\"URL\",\"https://rocky-garden-56471.herokuapp.com/breadcrum/lifecycle/register\"");// setting the httppara, the second parameter is the website you want to access
  delay(3000); 
  ShowSerialData();

  Serial1.println("AT+HTTPPARA=\"CONTENT\",\"application/json\"");
  delay(3000); 
  ShowSerialData();  

  Serial1.println("AT+HTTPDATA=1000,10000");
  delay(3000);
  ShowSerialData();

  Serial1.println("{\"device_info\":\"breadcrum-prototype-a\"}");
  delay(3000); 
  ShowSerialData();

  Serial1.println("AT+HTTPACTION=1");//submit the request //0:READ 1:POST 2:HEAD
  delay(10000);//the delay is very important, the delay time is base on the return from the website, if the return datas are very large, the time required longer.
  ShowSerialData();

  Serial1.println("AT+HTTPREAD");// read the data from the website you access
  delay(1000); 
  ShowSerialData();

  Serial1.println("");
  delay(100);
}

But the results I got from this was another error when attempting to post:

Setup CompleteAT+CSQ

+CSQ: 18,0

OK
AT+CGATT?

+CGATT: 1

OK
AT+SAPBR=3,1,"CONTYPE","GPRS"

OK
AT+SAPBR=3,1,"APN","everywhere"

OK
AT+SAPBR=1,1

OK
AT+SAPBR=2,1

+SAPBR: 1,1,"19.177.18.205"

OK
AT+HTTPINIT

OK
AT+HTTPPARA="CID",1

OK
AT+HTTPPARA="URL","https://rocky-garden-56471.herokuapp.com/breAT+HTTPPARA="CONTENT","application/json"

OK
AT+HTTPDATA=1000,10000

DOWNLOAD

ERROR
AT+HTTPREAD

OK

EDIT 2: Following HTTPS commands:

 AT+CSQ

+CSQ: 18,0

OK
AT+CGATT?

+CGATT: 1

OK
AT+SAPBR=3,1,"CONTYPE","GPRS"

OK
AT+SAPBR=3,1,"APN","everywhere"

OK
AT+SAPBR=1,1

ERROR
AT+SAPBR=2,1

+SAPBR: 1,1,"31.94.203.234"

OK
AT+HTTPSSL=1

OK
AT+HTTPINIT

OK
AT+HTTPPARA="CID",1

OK
AT+HTTPPARA="URL","https://rocky-garden-56471.herokuapp.com/breAT+HTTPPARA="CONTENT","application/json"

OK
AT+HTTPDATA=100,10000

DOWNLOAD

ERROR
AT+HTTPREAD

OK
AT+HTTPTERM

OK

Answer 1

There is so many things wrong that I don't know where to start.

1. You are trying to use a URL in place of a hostname.
2. You are trying to connect to an HTTPS service which runs on port 443 not on port 80
3. HTTPS is encrypted. You are opening a plain TCP socket to an encrypted service.

Your whole methodology is wrong. You need to use the SIM900 HTTPS AT Command Set to get the SIM900 to perform an HTTPS request on your behalf rather than opening a socket and sending / receiving data.