arduino + GSM/GPRS SIM 900A cannot able to read a message Here I am using Arduino uno and GSM sim900A, I want to read sms from sim900A. But i am trying to read message, it is showing the empty values. I tried different methods, but no use. Here I have added my script. Please help me.

#include &lt;avr wdt.h=""&gt;  
String phoneSMS = "+91xxxxxxxxxx";  
String messageTxt;  
void setup()  
{  
Serial.begin(9600);  
delay(60000);  
srl_msg();  
}  
String srl_msg()  
{  
Serial.println("AT+CMGF=1\r");  
delay(1000);  
Serial.println("AT+CNMI=2,2,0,0,0");  
delay(1000);  
Serial.println("AT+CMGL=\"ALL\"\r"); // to read ALL the SMS in text mode  
delay(1000);  
char txtmsg2[100]; // AT command output  
String date = readSerial(txtmsg2);  
String value = date.substring(1, 50);  
messageTxt = "Internal - Heart Beat;";  
messageTxt.concat(value);  
Serial.println(value);  
SendSMS(messageTxt);  
}  
void loop()  
{  
}  
void SendSMS(String message)  
{  
Serial.print("at+cmgf=1\r");  
delay(1000);  
Serial.print("at+cmgs=\"");  
Serial.print(phoneSMS);  
Serial.println("\"");  
delay(1000);  
Serial.println(message);  
delay(1000);  
Serial.print((char)26);  
delay(15000); // AAN  
}  
String readSerial(char result[])  
{  
int i = 0;  
while (Serial.available() &gt; 0)  
{  
char inChar = Serial.read();  
if (inChar != '\r')  
{  
result[i] = inChar;  
i++;  
}  
}  
return result;  
}  


output is look like this:
AT+CMGF=1  

OK  

AT+CNMI=2,2,0,0,0  

OK
AT+CMGL="ALL"  

OK
Check you sim card inbox. I also had the same problem, and it turns out the sim card sms inbox capacity is full.
You can also try to use another library, here is one of them