#include <SoftwareSerial.h>
SoftwareSerial SIM800(2, 3);
int relay = 4;
void setup()
{
SIM800.begin(115200);
Serial.begin(115200);
pinMode(relay,OUTPUT);
delay(1500);
}
void loop()
{
while(SIM800.available()>0)
{
digitalWrite(relay,HIGH);
Serial.println("relay on");
delay(1000);
digitalWrite(relay,LOW);
Serial.println("relay off");
}
}