HTTP post request in JSON Format using SIM900 module

Question

I tried to send HTTP post requests to a server in JSON Format using a SIM900 module. But the code is not posting the data. While posting the data I'm getting the error response while initializing the server using the command:

{("AT+HTTPPARA=\"URL\",\"http://test.server/insert-path")}

I don't know what the error is and how to fix it. Please help me to fix this.

#include<SoftwareSerial.h>

SoftwareSerial client(2,3);

String testReading="{  \"testID\" : 1,  \"testLevel\" : 1, }";

void setup() {
  Serial.begin(9600);
  client.begin(9600);
  delay(1000);
  if(client.available()) {
    Serial.print("Connected");
  } else {
    Serial.print("Not Connected");
  }
  checkSignal();
  connectGPRS();
  postData();
  delay(1000);
}

void loop() {
  if(client.available()) {
    checkSignal();
    connectGPRS();
    postData();
    delay(1000);
  }
}

void connectGPRS() {
  client.println("AT+CGATT?");
  delay(1000);
  ShowSerialData();
  client.println("AT+SAPBR=3,1,\"CONTYPE\",\"GPRS\"");
  delay(1000);
  ShowSerialData();
  client.println("AT+SAPBR=3,1,\"APN\",\"www\"");
  //Using Indian Standard Vodafone Sim and so APN is www
  delay(1000);
  ShowSerialData();

  client.println("AT+SAPBR=1,1");
  delay(1000);
  ShowSerialData();

  client.println("AT+SAPBR=2,1");
  delay(1000);
  ShowSerialData();
}

void checkSignal() {
  client.println("AT+CSQ");
  delay(1000);
  ShowSerialData();
}

void ShowSerialData() {
  while(client.available()!=0)
    Serial.write(client.read());
}

void postData() {
  client.println("AT+HTTPINIT");
  delay(1000);
  ShowSerialData();

  client.println("AT+HTTPPARA=\"CID\",1");
  delay(1000);
  ShowSerialData();

  client.println("AT+HTTPPARA=\"URL\",\"http://test.server/insert-path");
  delay(1000);
  ShowSerialData();

  client.println("AT+HTTPPARA=\"CONTENT\",\"application/json");
  delay(1000);
  ShowSerialData();

  client.println("AT+HTTPDATA=99,10000");
  delay(1000);
  ShowSerialData;

  client.println(testReading);
  delay(1000);
  ShowSerialData;

  client.println("AT+HTTPACTION=1");
  delay(10000);
  while(!client.available());
  ShowSerialData();
}

Answer 1

Hi all use this code below for establishing HTTP connection with the server. And to neglect the 601 or 504 error use proper posting format. Here I'm using JSON format. I just gave manual data. Ignore those errors in HTTPINIT, AT+SAPBR=2,1. The data will be posted to the server

 #include<SoftwareSerial.h>

SoftwareSerial client(2,3);


String reading="{  \" : 1,  \"latitude\" : 12.983027,  \"longitude\" : 80.2594,  \"timestamp\" : 100,  }";

void setup()
{
  Serial.begin(9600);
  client.begin(9600);
  delay(500);

  if(client.available())
  {
    Serial.print("Connected");
  }
  else
  {
    Serial.print("NotConnected");
  }

  //initSIM();
  connectGPRS();
  connectHTTP();
}

void loop()
{

}



void connectGPRS()
{ 
  client.println("AT+SAPBR=3,1,\"Contype\",\"GPRS\"");
  delay(1000);
  ShowSerialData();

  client.println("AT+SAPBR=3,1,\"APN\",\"www\"");//APN
  delay(1000);
  ShowSerialData();

  client.println("AT+SAPBR=1,1");
  delay(1000);
  ShowSerialData();

  client.println("AT+SAPBR=2,1");
  delay(1000);
  ShowSerialData();
}

void connectHTTP()
{
  client.println("AT+HTTPINIT");
  delay(1000);
  ShowSerialData();

  client.println("AT+HTTPPARA=\"CID\",1");
  delay(1000);
  ShowSerialData();

  client.println("AT+HTTPPARA=\"URL\",\"http://xxx.xxx.xx/Listener/\"");//Public server IP address
  client.println("AT+HTTPPARA=\"URL\",\"http://testServer/Listener/\"");//Public server address
  delay(1000);
  ShowSerialData();

  client.println("AT+HTTPPARA=\"CONTENT\",\"application/json\"");
  delay(1000);
  ShowSerialData();


  client.println("AT+HTTPDATA=" + String(reading.length()) + ",100000");
  delay(1000);
  ShowSerialData();

  client.println(reading);
  delay(1000);
  ShowSerialData;

  client.println("AT+HTTPACTION=1");
  delay(1000);
  ShowSerialData();

  client.println("AT+HTTPREAD");
  delay(1000);
  ShowSerialData();

  client.println("AT+HTTPTERM");
  delay(1000);
  ShowSerialData;
}

void ShowSerialData()
{
  while(client.available()!=0)
  {
  Serial.write(client.read());
  delay(100);
  }
}

Answer 2

client.println(reading);
delay(1000);
ShowSerialData;

The above line of code would result in an error.