Hex packets over Wifi : Send Receive Question

Projects Programming
8

me myself I was only using code similar to this simple udp-send-receive-demo

#include <DebugTxtVar.h>

#include <ESP8266WiFi.h>
#include <WiFiUdp.h>
  
// Set WiFi credentials
#define WIFI_SSID "TheOtherESP"
#define WIFI_PASS "flashmeifyoucan"

char buttonState = 1;
int packetsize  = 0;

// UDP Buffer
char packetBuffer[UDP_TX_PACKET_MAX_SIZE];
 
// UDP
WiFiUDP UDP;
IPAddress remote_IP(192,168,4,1);
#define UDP_PORT 4210

void PrintFileNameDateTime() {
  Serial.println("Code running comes from file ");
  Serial.println(__FILE__);
  Serial.print("  compiled ");
  Serial.print(__DATE__);
  Serial.print(" ");
  Serial.println(__TIME__);  
}


boolean TimePeriodIsOver (unsigned long &periodStartTime, unsigned long TimePeriod) {
  unsigned long currentMillis  = millis();  
  if ( currentMillis - periodStartTime >= TimePeriod )
  {
    periodStartTime = currentMillis; // set new expireTime
    return true;                // more time than TimePeriod) has elapsed since last time if-condition was true
  } 
  else return false;            // not expired
}

unsigned long MyTestTimer = 0;                   // variables MUST be of type unsigned long
const byte    OnBoard_LED = 2;


void BlinkHeartBeatLED(int IO_Pin, int BlinkPeriod) {
  static unsigned long MyBlinkTimer;
  pinMode(IO_Pin, OUTPUT);
  
  if ( TimePeriodIsOver(MyBlinkTimer,BlinkPeriod) ) {
    digitalWrite(IO_Pin,!digitalRead(IO_Pin) ); 
  }
}

 
void setup() {
  Serial.begin(115200);
  Serial.println("Setup-Start");
  PrintFileNameDateTime();
 
  // Begin WiFi
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  WiFi.mode(WIFI_STA);
  
  // Connecting to WiFi...
  Serial.print("Connecting to ");
  Serial.print(WIFI_SSID);
  // Loop continuously while WiFi is not connected
  while (WiFi.status() != WL_CONNECTED)
  {
    delay(100);
    Serial.print(".");
  }
  
  // Connected to WiFi
  Serial.println();
  Serial.print("Connected! IP address: ");
  Serial.println(WiFi.localIP());
 
  // Begin UDP port
  UDP.begin(UDP_PORT);
  Serial.print("Opening UDP port ");
  Serial.println(UDP_PORT);
  
}
  
void loop() {
  BlinkHeartBeatLED(OnBoard_LED,100);

  if ( TimePeriodIsOver(MyTestTimer,2000) ) {
    if (buttonState == 1) {
      buttonState = 0;
      Serial.print("buttonState =");
      Serial.println(buttonState); 
    }
    else {
      buttonState = 1;      
      Serial.print("buttonState =");
      Serial.println(buttonState); 
    }
  // Send Packet
  UDP.beginPacket(remote_IP, UDP_PORT);
  UDP.write(buttonState);
  UDP.endPacket();
  Serial.println("UDP packed sended"); 
  delay(100);
  }  

  // Receive packet
  packetsize = UDP.parsePacket();
  UDP.read(packetBuffer, UDP_TX_PACKET_MAX_SIZE);
  
  if (packetsize){
    Serial.print("UDP-packet #");
    Serial.print(packetBuffer);
    Serial.print("# from IP");
    Serial.println(UDP.remoteIP() );
  }  
   
}

it is written for ESP8266 but the udp-part will be the same for ESP32

these are the commands for sending a string

  Udp.beginPacket(remoteIP, remotePort);
  Udp.write((const uint8_t*)UDP_Msg_SS.c_str(), UDP_Msg_SS.length() );
  Udp.endPacket();

as you can see for using the udp.write-function the string has to be type-casted into uint8_t anyway. So sending a few bytes with hexadecimal values should be pretty straight forward

best regards Stefan