Three Xbee synchronization blinking - arduino

Question

I'm doing synchronization blinking with three XBee module and Arduino Uno,
the first is master, second is slave/master and the other one is a slave.
The master is going to give the command for both slave/master and slave to blinking, and when the master is switch off, the slave/master will taking over his job giving the command to blinking.
But the slave/master didn't go so well because of the coding didn't right.
Can anyone take a look at my coding and show me what is wrong with my coding.
Master Coding =
#include <SoftwareSerial.h>
#define Dout 2
#define Din 3
//#define LED 9
SoftwareSerial XBee(Dout, Din);
//char XBee_message;
int MasterSignalSent = 0;
const long interval = 2500;
unsigned long previousMillis = 0;
void setup() {
Serial.begin(9600);
XBee.begin(9600);
pinMode(13, OUTPUT);
}
void loop(){
unsigned long currentMillis = millis();
if (currentMillis - previousMillis >= interval) {
Serial.println(currentMillis);
previousMillis = currentMillis;
{
delay(1500);
SendMasterSignal();//+
MasterSignalSent = 1;
delay(1000);
SendSyncSignal();//-
BlinkLed();
MasterSignalSent = 0;
}
}
}
void SendMasterSignal()
{
Serial.println("SendingMasterSignal. . .");
XBee.write('+');
}
void SendSyncSignal()
{
Serial.println("SendingSyncSignal. . .");
XBee.write('-');
}
void BlinkLed()
{
digitalWrite(13, HIGH);
delay(250);
digitalWrite(13, LOW);
//delay(2200);
}
Slave/Master Coding =
#include <SoftwareSerial.h>
#define Dout 2
#define Din 3
SoftwareSerial XBee (Dout, Din);
const long interval = 2500;
unsigned long previousMillis = 0;
int MasterSignalReceived = 0;
int ReceiveSyncSignal = 0;
int MasterSignalSent = 0;
char XBee_signal;
void setup() {
Serial.begin(9600);
XBee.begin(9600);
pinMode(13, OUTPUT);
}
void loop() {
unsigned long currentMillis = millis();
if (currentMillis - previousMillis >= interval) {
previousMillis = currentMillis;
while(XBee.available()){
XBee_signal = XBee.read();
Serial.println(XBee_signal);
delay(1500);
if (MasterSignalReceived == 0)
{
BecomeMaster();
}
else if (MasterSignalReceived == 1)
{
if (XBee_signal = '-'){
BlinkLed();
(MasterSignalReceived = 0);
}
else{
digitalWrite(13, LOW);
}
}
}
}
}
void BecomeMaster()
{
unsigned long currentMillis = millis();
if (currentMillis - previousMillis >= interval) {
Serial.println(currentMillis);
previousMillis = currentMillis;
{
delay(1500);
SendMasterSignal();
MasterSignalSent = 1;
delay(2500);
SendSyncSignal();
BlinkLed();
MasterSignalSent = 0;
}
}
}
void SendMasterSignal()
{
XBee.write('+');
Serial.println("SendMasterSignalDone");
}
void SendSyncSignal()
{
XBee.write('-');
Serial.println("SendSyncSignalDone");
}
void BlinkLed()
{
digitalWrite(13, HIGH);
delay(1000);
digitalWrite(13, LOW);
}
The slave is waiting for the command to blinking but the slave/master didn't send any command as the coding write when the master switches off.