Serial Example

//untested

#include <SoftwareSerial.h>

char data;
unsigned long previousMillis;
int interval = 5000;

// software serial port for esp8266
int rxPin = 2;
int txPin = 3;
SoftwareSerial espSerial (rxPin, txPin);

void setup() {
  // put your setup code here, to run once:
  // put your main code here, to run repeatedly:
  Serial.begin(9600);

  //setup software serial
  pinMode(rxPin, INPUT);
  pinMode(txPin, OUTPUT);
  espSerial.begin(9600);

}

void loop() {
    // get current time
    unsigned long currentMillis = millis();

    // send the AT command once very interval (5sec)
    if (currentMillis - previousMillis >= interval) {
        Serial.println("Sending AT Command");
        espSerial.print("AT+GMR\r\n");
        previousMillis = currentMillis;
    }

    // empty the RX buffer
    while (espSerial.available() > 0) {
        data = espSerial.read();
        Serial.print(data);
    }

}