How can I include a body while sending a POST request using HTTP AT commands with a SIM7000A module and an Arduino? - c++

Question

I'm crossposting this from where I posted it on the Arduino forum in hopes that maybe someone here has an answer. I am working on a project that involves sending POST requests to a Twilio function using an Arduino Uno and a SIMCOM SIM7000A breakout board using AT commands. So far with the Uno, I can only POST an empty request that contains headers but no body. The following code is a test sketch where I am POSTing to a RequestBin repository.
#include <AltSoftSerial.h>
unsigned char data = 0;
AltSoftSerial SIM7000;
char incomingChar;
void setup() {
Serial.begin(9600);
SIM7000.begin(19200);
// put your setup code here, to run once:
SIM7000.print("AT+CMGF=1\r"); //put in text mode
delay(100);
SIM7000.print("AT+CGDCONT=1\"IP\",\"super\"\r"); //create profile. "super" is APN for twilio super sim
delay(1000);
SIM7000.print("AT+COPS=1,2,\"310410\"\r"); //log on to AT&T network
delay(5000);
SIM7000.print("AT+SAPBR=3,1,\"APN\",\"super\"\r"); //create SAPBR profile. same APN.
delay(300);
SIM7000.print("AT+SAPBR=1,1\r");
delay(2000);
Serial.println("Setup complete. Module should be online and fast-blinking\n from successful SAPBR profile setup.\n Entering loop. Send \"CHECK\" to test POST");
}
void loop() {
SIM7000.print("AT+CMGL\r");
if (SIM7000.available() > 0) {
incomingChar = SIM7000.read();
if (incomingChar == 'C') {
delay(10);
Serial.print(incomingChar);
incomingChar = SIM7000.read();
if (incomingChar == 'H') {
delay(10);
Serial.print(incomingChar);
incomingChar = SIM7000.read();
if (incomingChar == 'E') {
delay(10);
Serial.print(incomingChar);
incomingChar = SIM7000.read();
if (incomingChar == 'C') {
delay(10);
Serial.print(incomingChar);
incomingChar = SIM7000.read();
if (incomingChar == 'K') {
delay(10);
Serial.print(incomingChar);
incomingChar = "";
Serial.println(F("\nGOOD CHECK"));
Serial.println(F("SENDING POST REQUEST NOW")) ;
sendText();
Serial.println("POST SENT");
return;
}
}
}
}
}
}
incomingChar = "";
return;
}
void sendText()
{
SIM7000.print("AT+HTTPINIT\r");
delay(1000);
getResponse();
SIM7000.print("AT+HTTPPARA=\"CID\",1\r");
delay(1000);
getResponse();
SIM7000.print("AT+HTTPPARA=\"URL\",\"http://engt62k9mgbgo.x.pipedream.net\"\r");
delay(1000);
getResponse();
SIM7000.print("AT+HTTPPARA=\"CONTENT\",\"text/plain\"\r");
delay(1000);
getResponse();
SIM7000.print("AT+HTTPDATA=100,5000\r\n");
delay(100);
getResponse();
SIM7000.print("\"TEST MESSAGE\"\r\n");
SIM7000.print("\r\n");
delay(5000);
getResponse();
SIM7000.print("AT+HTTPACTION=1\r");
delay(1000);
getResponse();
SIM7000.print("AT+HTTPTERM\r");
getResponse();
}
void getResponse()
{
if (SIM7000.available())
{
while (SIM7000.available())
{
data = SIM7000.read();
Serial.write(data);
}
data = 0;
}
}
//NOV 3 2020, note: need to include AT command AT+CMGD=0,4 for routinely deleting messages
//message storage limited and not automatically overwritten
I've included the output on the Serial monitor below.
Output on Serial Monitor
I'm thinking that the problem lies between
SIM7000.print("AT+HTTPDATA=100,5000\r\n");
and
SIM7000.print("AT+HTTPACTION=1\r");
You can see on the output where it prompts for DOWNLOAD, but the "TEST MESSAGE" that I try to insert here doesn't go. I've also attached a screenshot of the RequestBin output to show that it's showing up as an empty POST with nothing but headers and a content length of 0. Output in RequestBin
When I've done similar POST requests using the same SIM7000A module with the same AT commands on PuTTY via USB, all I have to do is enter my text during the time specified in the AT+HTTPDATA command and hit enter. Whatever I enter during that time as it says "DOWNLOAD" shows up as the body of my POST. But I have as of yet been unable to do the same using the Uno.
Any help you can offer is much appreciated.

Answer 1

First of all, you must to send CR NL char after all AT commands...
SIM7000.print("AT+HTTPDATA=100,5000\r\n");
Note: \r and \n = CR and NL respectively.
Second, try the steps below:
// SEND HTTP PROCESS
SIM7000.println("AT+HTTPINIT\r\n");
delay(1500);
Serial.println(SIM7000.readString());
SIM7000.println("AT+HTTPPARA=\"CID\",1\r\n");
delay(1500);
Serial.println(SIM7000.readString());
char httpSend[105] = "[URL]";
SIM7000.println(httpSend + String("\r\n"));
delay(1500);
Serial.println(SIM7000.readString());
SIM7000.println("AT+HTTPSSL=1\r\n"); // THIS LINE FOR SSL URL
delay(1500);
Serial.println(SIM7000.readString());
SIM7000.println("AT+HTTPACTION=0\r\n"); //GET REQUEST = 0 | POST REQUEST = 1
delay(7000);
Serial.println(SIM7000.readString());
SIM7000.println("AT+HTTPREAD\r\n");
delay(1500);
Serial.println(SIM7000.readString());
SIM7000.println("AT+HTTPTERM\r\n");
delay(1500);
Serial.println(SIM7000.readString());

Answer 2

Try adding ctrl-z Character (decimal 26) to the end of the data buffer you are sending after seeing DOWNLOAD.