Unable to send new message through RF433 transceiver and vitrualwire library

I am doing a project that combines hand gesture control (using an accelerometer) with obstacle avoidance (using an ultrasonic sensor)
So far, I successfully linked the hand gesture control with the dc motors powering the robot and I am able to control it remotely (though with the help of a code I found online that already had four messages sent through the rf module that I managed to utilize for forward, backward, left and right)
The issue I am having currently is how to add the obstacle avoidance capability of the robot to the code.
The concept is that the robot should be controllable remotely and when a push button is pressed; it performs its operation automatically

The transmitter code is shown below:

#include <VirtualWire.h>

int xPin=0;
int yPin=1;
int zPin=2;

int ledPin=13;//led on pin 13 is ON except when transmitter is parallel to the ground

void setup() 
{
  Wire.begin();//Initialise the serial connection debugging
  lcd.begin(16, 2);
  vw_setup(2000);//Bits per second
  pinMode(ledPin,OUTPUT);
  Serial.begin(9600);//Initialise the serial connection debugging
}

void loop() 
{
  int xval=analogRead(xPin);
  int yval=analogRead(yPin);
  int zval=analogRead(zPin);
  
  Serial.print("xval=");
  Serial.println(xval);
  
  Serial.print("yval=");
  Serial.println(yval); 

  Serial.print("zval=");
  Serial.println(zval); 
  
  delay(1000); //used to display values after 1s delay
  
  Serial.print("\n");
  
  if ((xval>330 && xval<370) && (yval>330 && yval<370)) //stationary or stop(transmitter parallel to ground)
  {
    digitalWrite(ledPin,LOW);
    send("s");
  } 
  else 
  { 
    if ((xval>371 && xval<420) && (yval>330 && yval<370)) //forward(transmitter tilted forward)
    {
      digitalWrite(ledPin,HIGH);
      send("f");
      
    }
    if ((xval>280 && xval<329) && (yval>330 && yval<370)) //backward(transmitter tilted backward)
    {
      digitalWrite(ledPin,HIGH);
      send("a");
      
    }
    if ((xval>330 && xval<370) && (yval>371 && yval<420)) //left(transmitter tilted to left)
    {
      digitalWrite(ledPin,HIGH);
      send("l");
     }
     if ((xval>330 && xval<370) && (yval>280 && yval<329))//right(transmitter tilted to right)
    {
      digitalWrite(ledPin,HIGH);
      send("r");
      
    }
  }
  //delay(1000);
  if ((zval>280 && zval<310) )//right(transmitter tilted to right)
    {
      digitalWrite(ledPin,HIGH);
      send("z");
      
    }
  
}


void send(char *message)//send function definition
{
  vw_send((uint8_t *)message, strlen(message));
  vw_wait_tx(); // Wait until the whole message is gone
}

and the receiver code is

#include <VirtualWire.h>
byte message[VW_MAX_MESSAGE_LEN]; // a buffer to store the incoming messages
byte messageLength = VW_MAX_MESSAGE_LEN; // the size of the message
int relay=12;
int lm = 4;
int lmr = 5;
int rm = 6;
int rmr = 7;
int ledPin = 13; //led on pin 13 is ON except when bot is stationary

  // defines pins numbers
 const int trigPin = 9;
 const int echoPin = 10; 
 // defines variables
 long duration;
 int distance; 
 
void setup()
{
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
  pinMode(lm, OUTPUT);
  pinMode(lmr, OUTPUT);
  pinMode(rm, OUTPUT);
  pinMode(rmr, OUTPUT);
  pinMode(relay, OUTPUT);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  
 
  vw_setup(2000); // Bits per sec
  vw_rx_start(); // Start the receiver
}
void loop()
{
  uint8_t buf[VW_MAX_MESSAGE_LEN];
  uint8_t buflen = VW_MAX_MESSAGE_LEN;
  if (vw_get_message(buf, & buflen)) // Non-blocking
  {
    int i;

    Serial.print("Got: ");//debugging

    for (i = 0; i < buflen; i++)
    {
       Serial.print(buf[i],HEX);//You may also use integer values debugging
      Serial.print(' ');// debugging

      if (buf[i] == 0x73) //Stationary
      {
        digitalWrite(lm, LOW);
        digitalWrite(lmr, LOW);
        digitalWrite(rm, LOW);
        digitalWrite(rmr, LOW);
        delay(5000);
        
 
        if (buf[i] == 0x73) 

        digitalWrite(ledPin, LOW);
      }
      else
      {
        if (buf[i] == 0x66) //Forward
        {
          digitalWrite(lm, LOW);
          digitalWrite(lmr, HIGH);
          digitalWrite(rm, HIGH);
          digitalWrite(rmr, LOW);
          digitalWrite(relay, HIGH);
          digitalWrite(ledPin, HIGH);
        }

        if (buf[i] == 0x61) //Backward
        {
          digitalWrite(lm, HIGH);
          digitalWrite(lmr, LOW);
          digitalWrite(rm, LOW);
          digitalWrite(rmr, HIGH);

          digitalWrite(ledPin, HIGH);
        }

        if (buf[i] == 0x72) //Left
        {
          digitalWrite(lm, LOW);
          digitalWrite(lmr, HIGHE);
          digitalWrite(rm, LOW);
          digitalWrite(rmr, LOW);
          digitalWrite(ledPin, HIGH);
        }

        if (buf[i] == 0x6C) //Right
        {
          digitalWrite(lm, LOW);
          digitalWrite(lmr, LOW);
          digitalWrite(rm, HIGH);
          digitalWrite(rmr, LOW);
          digitalWrite(ledPin, HIGH);
        }
      }
    }
    Serial.print("\n");// debugging
  }
  //delay(1000);
}

Can someone explain to me the relationship between the "send s" from the transmitter code and the 0X73 in the receiver.
Thank you.
your quick responses would be appreciated

0x73 is the hexadecimal representation of the ASCII code for the letter 's'.

Thank you very much. You just solved my problem