ATMega 328p: Sending TCP packet using SIM808, SIM900

tcp.ino

#include <SoftwareSerial.h>
SoftwareSerial SIM(8, 9);

int8_t answer;
int onModulePin = 2;
char aux_str[50];
char ip_data[40] = "Test string from GPRS shieldrn";
void setup() {
	pinMode(onModulePin, OUTPUT);
	SIM.begin(9600);
	Serial.begin(9600);
	Serial.println("Starting...");
	power_on();
	delay(3000);
	// sets the PIN code
	sendATcommand2("AT+CPIN=****", "OK", "ERROR", 2000);
	delay(3000);
	Serial.println("Connecting to the network...");
	while (sendATcommand2("AT+CREG?", "+CREG: 0,1", "+CREG: 0,5", 1000) == 0);
}
void loop() {
	// Selects Single-connection mode
	if (sendATcommand2("AT+CIPMUX=0", "OK", "ERROR", 1000) == 1)
	{
		// Waits for status IP INITIAL
		while (sendATcommand2("AT+CIPSTATUS", "INITIAL", "", 500) == 0);
		delay(5000);

		// Sets the APN, user name and password
		if (sendATcommand2("AT+CSTT=\"www\",\"\",\"\"", "OK", "ERROR", 30000) == 1)
		{
			// Waits for status IP START
			while (sendATcommand2("AT+CIPSTATUS", "START", "", 500) == 0);
			delay(5000);

			// Brings Up Wireless Connection
			if (sendATcommand2("AT+CIICR", "OK", "ERROR", 30000) == 1)
			{
				// Waits for status IP GPRSACT
				while (sendATcommand2("AT+CIPSTATUS", "GPRSACT", "", 500) == 0);
				delay(5000);

				// Gets Local IP Address
				if (sendATcommand2("AT+CIFSR", ".", "ERROR", 10000) == 1)
				{
					// Waits for status IP STATUS
					while (sendATcommand2("AT+CIPSTATUS", "IP STATUS", "", 500) == 0);
					delay(5000);
					Serial.println("Openning TCP");

					// Opens a TCP socket
					if (sendATcommand2("AT+CIPSTART=\"TCP\",\"104.130.162.53\",\"1997\"", "CONNECT OK", "CONNECT FAIL", 30000) == 1)
					{
						Serial.println("Connected");

						// Sends some data to the TCP socket
						sprintf(aux_str, "AT+CIPSEND=%d", strlen(ip_data));
						if (sendATcommand2(aux_str, ">", "ERROR", 10000) == 1)
						{
							sendATcommand2(ip_data, "SEND OK", "ERROR", 10000);
						}

						// Closes the socket
						sendATcommand2("AT+CIPCLOSE", "CLOSE OK", "ERROR", 10000);
					}
					else
					{
						Serial.println("Error openning the connection");
					}
				}
				else
				{
					Serial.println("Error getting the IP address");
				}
			}
			else
			{
				Serial.println("Error bring up wireless connection");
			}
		}
		else
		{
			Serial.println("Error setting the APN");
		}
	}
	else
	{
		Serial.println("Error setting the single connection");
	}

	sendATcommand2("AT+CIPSHUT", "OK", "ERROR", 10000);
	delay(10000);
}

void power_on() {

	uint8_t answer = 0;

	// checks if the module is started
	answer = sendATcommand2("AT", "OK", "OK", 2000);
	if (answer == 0)
	{
		// power on pulse
		digitalWrite(onModulePin, HIGH);
		delay(3000);
		digitalWrite(onModulePin, LOW);

		// waits for an answer from the module
		while (answer == 0) {     // Send AT every two seconds and wait for the answer
			answer = sendATcommand2("AT", "OK", "OK", 2000);
		}
	}

}

int8_t sendATcommand2(char* ATcommand, char* expected_answer1, char* expected_answer2, unsigned int timeout) {

	uint8_t x = 0, answer = 0;
	char response[100];
	unsigned long previous;

	memset(response, ' ', 100);    // Initialize the string

	delay(100);

	while (SIM.available() > 0) SIM.read();    // Clean the input buffer

	SIM.println(ATcommand);    // Send the AT command

	x = 0;
	previous = millis();

	// this loop waits for the answer
	do {
		// if there are data in the UART input buffer, reads it and checks for the asnwer
		if (SIM.available() != 0) {
			response[x] = SIM.read();
			x++;
			// check if the desired answer 1  is in the response of the module
			if (strstr(response, expected_answer1) != NULL)
			{
				answer = 1;
			}
			// check if the desired answer 2 is in the response of the module
			else if (strstr(response, expected_answer2) != NULL)
			{
				answer = 2;
			}
		}
	}
	// Waits for the asnwer with time out
	while ((answer == 0) && ((millis() - previous) < timeout));

	return answer;
}