Data separation in UDP connection

navidh91 · June 27, 2022, 10:19am

Hello
I connected two Arduinos with udp connection. Communicated and there is no problem. Because the temperature and humidity sensor is installed on the transmitter side. I want the data receiver to reach me separately and be sent to the server. For example, between the values that are sent, if the word "Temperature" is sent before the temperature data, Ardino realizes that the value sent is related to the temperature and sends it to the mqtt server.

Thank you for your help.

This is the sender's code:

/*  AHT10 Sensor              Active
    Scheduler                 Active
    Wifi Connectivity         Active
    HTTP UDP Stack            Active
    UID                       Active
    Software Watchdog         Active
    Masoud
    January 05, 2022
*/

#include <Arduino.h>
#include <Wire.h>
#include <AHT10.h>
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <ArduinoOTA.h>
#include <WiFiUdp.h>


//Prototyping
void tempSense();                        // Prototype so PlatformIO doesn't complain

// Set WiFi credentials
#define WIFI_SSID "Ang-Sim"
#define WIFI_PASS "qwerty2580"

// UDP
WiFiUDP UDP;
IPAddress remote_IP(192,168,1,1);
#define UDP_PORT 4210

// UDP Buffer
char packet[255];
char reply[] = "Packet received!";


const String prefix  = "/angizeh/toossab/1/4";
const char* clientID = "AirHumidityNode06";



String topic = "";
String message = "";

// AHT Sensor
AHT10 myAHT10(AHT10_ADDRESS_0X38);



//Timer Variables
long Day = 0;
int Hour = 0;
int Minute = 0;
int Second = 0;
int SecondStamp = 0;
int Once = 0;
int cnt=10;
int powerFlag;


//Variables
int strobe = 0;
float airTemperature = 0, airHumidity = 0;

WiFiClient wclient;                        
PubSubClient client(wclient);

void setup() {
   
  // Setup serial port
  Serial.begin(115200);
  Serial.println();
  
  // Begin WiFi
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  WiFi.mode(WIFI_AP_STA);
  
  while (myAHT10.begin() != true)
    {
      Serial.println(F("AHT10 not connected or fail to load calibration coefficient")); //(F()) save string to flash & keeps dynamic memory free
      delay(5000);
    }
  Serial.println(F("AHT10 OK"));

  // Connecting to WiFi...
  Serial.print("Connecting to ");
  Serial.print(WIFI_SSID);
  // Loop continuously while WiFi is not connected

  ArduinoOTA.setHostname("AirHumidityNode");
  ArduinoOTA.onStart([]() {
    String type;
    if (ArduinoOTA.getCommand() == U_FLASH) {
      type = "sketch";
    } else { // U_FS
      type = "filesystem";
    }

    // NOTE: if updating FS this would be the place to unmount FS using FS.end()
    Serial.println("Start updating " + type);
  });
  ArduinoOTA.onEnd([]() {
    Serial.println("\nEnd");
  });
  ArduinoOTA.onProgress([](unsigned int progress, unsigned int total) {
    Serial.printf("Progress: %u%%\r", (progress / (total / 100)));
  });
  ArduinoOTA.onError([](ota_error_t error) {
    Serial.printf("Error[%u]: ", error);
    if (error == OTA_AUTH_ERROR) {
      Serial.println("Auth Failed");
    } else if (error == OTA_BEGIN_ERROR) {
      Serial.println("Begin Failed");
    } else if (error == OTA_CONNECT_ERROR) {
      Serial.println("Connect Failed");
    } else if (error == OTA_RECEIVE_ERROR) {
      Serial.println("Receive Failed");
    } else if (error == OTA_END_ERROR) {
      Serial.println("End Failed");
    }
  });
  ArduinoOTA.begin();
  Serial.print("\n");

  Serial.println("OTA Ready");
  
  
    while (WiFi.status() != WL_CONNECTED){
//    ESP.wdtFeed();            
//    ESP.wdtDisable();                     
//    delay(500);
    Serial.print(".");
    delay(500);
//    cnt--;
//   if(cnt==0){
//    ESP.wdtDisable();
//    #ifdef SOFT_WATCHDOG
//    ESP.wdtEnable(0);
//    #endif  
//    while(1);
  delay(1000);
}

  
  // Connected to WiFi
  Serial.println();
  Serial.print("Connected! IP address: ");
  Serial.println(WiFi.localIP());

 client.setServer(mqttServerName, mqttport);
  client.setCallback(onMessageArrived);
//  
// while (!client.connected()){
//    delay(1000);
//    Serial.println("Connecting To Server ...");
// 
//    if (client.connect(clientID, mqttuser, mqttpass, toCharArray(prefix + "/Will"), 1, true, toCharArray("Bye"), true))
//    {
//      Serial.println("Connected To Server");
//    } 
//    else 
//    {
//      Serial.print("failed with state ");
//      Serial.print(client.state());
//      delay(2000);
//    }
//  }
  
   // Begin UDP port
  UDP.begin(UDP_PORT);
  Serial.print("Opening UDP port ");
  Serial.println(UDP_PORT);
}
  
void loop() {
  ESP.wdtFeed(); 
  ArduinoOTA.handle();
  tempSense();
   int a=analogRead(A0);
  int b=map(a,0,1023,0,255);
  Serial.println(b);
  if(b<=250){
    Serial.println("AC Power Disconnected");
    client.publish(toCharArray("/angizeh/toossab/1/4/ACPower:"), toCharArray("Disconnected"));
    //Serial.print(b);
    powerFlag = 0;
    delay(500);
  }
  if(b>250){
    Serial.println("AC Power Connected");
    client.publish(toCharArray("/angizeh/toossab/1/4/ACPower:"), toCharArray("Connected"));
    //Serial.print(b);
    powerFlag = 1;
    delay(500);
  }
  rtUDP();
  delay(2000);
}

//Functions
//=======================================================================
void tempSense(){
//   if (!client.connected()) {
//    ESP.wdtFeed(); 
//    Serial.print("reconnect");
//  reconnect();
//   } else { 
  **airTemperature = myAHT10.readTemperature(); airHumidity = myAHT10.readHumidity();**
**  Serial.print("Timestamp; ");Serial.print(Minute);Serial.print(":");Serial.println(Second);**
**  Serial.print("Device; ");Serial.print("Chip ID: ");Serial.print(ESP.getChipId());Serial.print(" MAC Address: ");Serial.println(WiFi.macAddress());**
**  Serial.print("Temperature: ");Serial.print(airTemperature);Serial.println(" degrees C");**
**  client.publish(toCharArray("/angizeh/toossab/1/4/Temperature"), toCharArray(String(airTemperature)));**
**  Serial.println("Published");**
**  Serial.print("Pressure: ");Serial.print(airHumidity);Serial.println(" RH %");**
**  client.publish(toCharArray("/angizeh/toossab/1/4/Humidity"), toCharArray(String(airHumidity)));**
**  UDP.print("Crestron connect");**
**  UDP.endPacket();**
**  UDP.write(toCharArray(String(airHumidity)));**
**  UDP.endPacket();**
**  Serial.println("Published");**
**   //}**
**}**

boolean reconnect() {
   while (WiFi.status() != WL_CONNECTED){
    ESP.wdtFeed();            
    ESP.wdtDisable();                     
    delay(500);
    Serial.print(".");
    delay(500);
    cnt--;
        if(cnt==0){
    ESP.wdtDisable();
    #ifdef SOFT_WATCHDOG
    ESP.wdtEnable(0);
    #endif  
    while(1);  
  }
  }
  delay(1000);
  if (client.connect(clientID, mqttuser, mqttpass, toCharArray(prefix + "/Will"), 1, true, toCharArray("Disconnected"), true)) {
    client.setCallback(onMessageArrived);
    Serial.print("***Disconnected***");
  return client.connected();
  }
}

char* toCharArray(String str) {
  return &str[0];
}

void onMessageArrived(char* t, byte* m, unsigned int length) {
  topic = String(t);
  message = String((char*)m);
  message = message.substring(0, length);

  if (message == "HELLO") {
    Serial.println("Hello client");
    client.publish(toCharArray(prefix + "/server"), toCharArray("HELLO"));
    Serial.println("Hello server");
  }
}

void rtUDP(){
  // Send Packet
   ESP.wdtFeed();
  UDP.beginPacket(remote_IP, UDP_PORT);
  if(powerFlag == 0){
    int data = 0;
  UDP.write(data);
  UDP.endPacket();
  Serial.println(data + "Sent");
  }
  if(powerFlag == 1){
    int data = 1;
  UDP.write(data);
  UDP.endPacket();
  Serial.println(data + "Sent");
  }
  Serial.print("UDP transmitted ");
  //Serial.println(data++);
  delay(5000);
}// END
//=======================================================================

This is the recipient side code:

#include <Arduino.h>
#include <ESP8266WiFi.h>
#include <WiFiUdp.h>
#include <SoftwareSerial.h>
#include<ESP8266WebServer.h>
#include <PubSubClient.h>





#define rxPin D6
#define txPin D5
SoftwareSerial mySerial(rxPin,txPin);

#define ssid "Ang-Sim"
#define pass "qwerty2580"

//// UDP
WiFiUDP UDP;
IPAddress local_ip(192, 168, 1, 1);
IPAddress gateway(192, 168, 1, 1);
IPAddress subnet(255, 255, 255, 0);
#define UDP_PORT 4210

ESP8266WebServer server(80);

const char* wifi = "Ang-IoT";
const char* password = "qwerty2580";

const String prefix  = "/angizeh/toossab/1/4";
const char* clientID = "AirHumidityNode06";

const char* mqttServerName = "";
const int   mqttport = ;
const char* mqttuser =  "";
const char* mqttpass =  "";

WiFiClient wclient;                        
PubSubClient client(wclient);


String topic = "";
String message = "";


// UDP Buffer
char packet[255];
char reply[] = "Packet received!";
char packetBuffer[UDP_TX_PACKET_MAX_SIZE];
int ACState = 3;
int newACState = 3;
int cnt=10;


void setup()
{
  
   // Setup serial port
  Serial.begin(115200);
  Serial.println();
  // Begin Access Point
  Serial.println("UDP server\nStarting access point...");
  WiFi.mode(WIFI_AP_STA);
  WiFi.softAPConfig(local_ip, gateway, subnet);
  WiFi.softAP(ssid, pass);
  IPAddress myIP = WiFi.softAPIP();
  Serial.print("AP IP address: ");
  Serial.println(myIP); 
  // Begin listening to UDP port
  UDP.begin(UDP_PORT);
  Serial.print("Listening on UDP port ");
  Serial.println(UDP_PORT); 
  STA();

  mySerial.begin(9600);

  Serial.println("Initializing...");
  delay(1000);

  mySerial.println("AT");
  updateSerial();
  delay(500);
  mySerial.println("AT+CSQ"); 
  updateSerial();
  delay(500);
   mySerial.println("AT+CSCS?"); 
  updateSerial();
  delay(500);
  mySerial.println("AT+CREG=1"); 
  updateSerial();
  delay(500);
  mySerial.println("AT+CMGF=1"); 
  updateSerial();
  delay(500);
  mySerial.println("AT+CMGF?"); 
  updateSerial();
  delay(500);
  mySerial.println("AT+CMGS=\"+989390726967\"");
  updateSerial();
  delay(500);
  
  delay(3000);
}

void loop()
{
  server.handleClient();
   if(UDP.parsePacket()) {
      UDP.read(packetBuffer, UDP_TX_PACKET_MAX_SIZE);   
      if(strcmp(packetBuffer,"Crestron connect")==0){
        UDP.read(packetBuffer, UDP_TX_PACKET_MAX_SIZE);
        Serial.println(packetBuffer); 
      client.publish(toCharArray("/angizeh/toossab/1/4/Humidity"), toCharArray(String(packetBuffer)));
        Serial.println("Published");
      }else{
      //Serial.println((int) packetBuffer[0]); 
      newACState = (int) packetBuffer[0];
//      Serial.print(ACState);
//      Serial.print(newACState);
      if (ACState != newACState){
        ACState = newACState;
        Serial.println("UDP packet received ");
        if (ACState == 1){
        client.publish(toCharArray("/angizeh/toossab/1/4/ACPower"), toCharArray("Connected"));
        Serial.println("Published");
        Serial.println ("AC Connected");
         mySerial.println("AT+CMGS=\"+989390726967\"");
         updateSerial();
        delay(500);
        mySerial.print("AC Connected"); 
        updateSerial();
        mySerial.write(26);
        delay(500);
      }
      if (ACState == 0) {
        client.publish(toCharArray("/angizeh/toossab/1/4/ACPower"), toCharArray("Disconnected"));
        Serial.println("Published");
        Serial.println ("AC Disconnected");
         mySerial.println("AT+CMGS=\"+989390726967\"");
         updateSerial();
        delay(500);
        mySerial.print("AC Disconnected"); 
        updateSerial();
        mySerial.write(26);
        delay(500);    
      }
     }
      }
  
  updateSerial();
}
}

void updateSerial()
{
  delay(500);
  while (Serial.available()) 
  {
    mySerial.write(Serial.read());
  }
  while(mySerial.available()) 
  {
    Serial.write(mySerial.read());
  }
}

void STA()
{
      WiFi.begin(wifi, password);

    while(WiFi.status()!= WL_CONNECTED)
    {
      Serial.print(".");
      delay(500);
    }

      Serial.println();

      Serial.print(".....Connect to the WiFi and open the IP address given below.....");
      Serial.println("IP address:-");
      Serial.println(WiFi.localIP());

      server.on ("/", [] () {server.send(200, "text/plain", "HELLO THERE");});
      server.begin();

      client.setServer(mqttServerName, mqttport);
  client.setCallback(onMessageArrived);
//  
 while (!client.connected()){
    delay(1000);
    Serial.println("Connecting To Server ...");
 
    if (client.connect(clientID, mqttuser, mqttpass, toCharArray(prefix + "/Will"), 1, true, toCharArray("Bye"), true))
    {
      Serial.println("Connected To Server");
    } 
    else 
    {
      Serial.print("failed with state ");
      Serial.print(client.state());
      delay(2000);
    }
  }
   client.publish(toCharArray("/angizeh/toossab/1/4/Temperature"), toCharArray("Hellooo"));
       Serial.println("Published");
}


char* toCharArray(String str) {
  return &str[0];
}

void onMessageArrived(char* t, byte* m, unsigned int length) {
  topic = String(t);
  message = String((char*)m);
  message = message.substring(0, length);

  if (message == "HELLO") {
    Serial.println("Hello client");
    client.publish(toCharArray(prefix + "/server"), toCharArray("HELLO"));
    Serial.println("Hello server");
  }
}


boolean reconnect() {
   while (WiFi.status() != WL_CONNECTED){
    ESP.wdtFeed();            
    ESP.wdtDisable();                     
    delay(500);
    Serial.print(".");
    delay(500);
    cnt--;
        if(cnt==0){
    ESP.wdtDisable();
    #ifdef SOFT_WATCHDOG
    ESP.wdtEnable(0);
    #endif  
    while(1);  
  }
  }
  delay(1000);
  if (client.connect(clientID, mqttuser, mqttpass, toCharArray(prefix + "/Will"), 1, true, toCharArray("Disconnected"), true)) {
    client.setCallback(onMessageArrived);
    Serial.print("***Disconnected***");
  return client.connected();
  }
}

navidh91 · June 27, 2022, 10:37am

In this line, the receiver side is supposed to compare the received string value udp, and if it does not match, the correct comparison will be done, but the line after else is also read.

 if(strcmp(packetBuffer,"Crestron connect")==0){
        UDP.read(packetBuffer, UDP_TX_PACKET_MAX_SIZE);
        Serial.println(packetBuffer); 
      client.publish(toCharArray("/angizeh/toossab/1/4/Humidity"), toCharArray(String(packetBuffer)));
        Serial.println("Published");
      }else{
      //Serial.println((int) packetBuffer[0]); 
      newACState = (int) packetBuffer[0];
//      Serial.print(ACState);
//      Serial.print(newACState);
      if (ACState != newACState){
        ACState = newACState;
        Serial.println("UDP packet received ");
        if (ACState == 1){
        client.publish(toCharArray("/angizeh/toossab/1/4/ACPower"), toCharArray("Connected"));
        Serial.println("Published");
        Serial.println ("AC Connected");
         mySerial.println("AT+CMGS=\"+989390726967\"");
         updateSerial();
        delay(500);
        mySerial.print("AC Connected");
        updateSerial();
        mySerial.write(26);
        delay(500);
      }
      if (ACState == 0) {
        client.publish(toCharArray("/angizeh/toossab/1/4/ACPower"), toCharArray("Disconnected"));
        Serial.println("Published");
        Serial.println ("AC Disconnected");
         mySerial.println("AT+CMGS=\"+989390726967\"");
         updateSerial();
        delay(500);
        mySerial.print("AC Disconnected");
        updateSerial();
        mySerial.write(26);
        delay(500);    
      }
     }
      }

StefanL38 · June 27, 2022, 12:02pm

I don't understand this. It sounds contradictionary

something does not match and then the correct comparison is done?????

but (then?) the "else" is also read?????

You should take time to expand what you want to say into 5 sentences
or write down an example for each case

best regards Stefan

navidh91 · June 27, 2022, 4:32pm

Excuse me for explaining in a hurry.
In general, what I want to do is connect several arduinoes (which are actually connected to each of the temperature and humidity sensors) using UDP to an arduino that acts as a data distributor on the server, and that arduino send data to mqtt server separately. Because all devices send data together, it is not clear which data is sent from which Arduino. I have trouble separating the data I get from different arduinoes with udp. How can I write code that separates the data coming from each arduino?
And in the next step, the temperature and humidity data sent from each device should be separated.

StefanL38 · June 27, 2022, 9:35pm

what exact type of microcontroller are you using?

combine the data with a device=number
ID=1,Temp=12.34, Hum=43%
ID=2,Temp=32.98, Hum=56%
etc.

parsing the code for identifiers and delimter-chacters
search where in the message is the "ID=" characters behind until comma is ID-number
search where in the message is the "Temp=" characters behind until comma is temperature-vaule
etc.

how do your arduinos send data over UDP?

best regards Stefan

Topic		Replies	Views
Simple UDP sending over ethernet Programming	36	1148	August 23, 2025
Bi-directional data over LAN Networking, Protocols, and Devices	24	681	January 31, 2025
Data exchange with 2 Arduino Uno via UDP Networking, Protocols, and Devices	8	2485	August 17, 2021
Server TCP e client TCP nello stesso Sketch - scambio dati tra 2 Arduini Software	23	1150	June 10, 2023
Uno Rev2 Wifi server/client connection problems UNO WiFi Rev2	10	231	July 7, 2025

Data separation in UDP connection

Related topics