#include <Wire.h>
void setup() {
Wire.begin();
Serial.begin(9600);
}
void loop() {
String message;
Serial.println("Send message: ");
while(Serial.available() == 0);
message = Serial.readString();
Wire.beginTransmission(9);``
Wire.write(message.c_str());
Wire.endTransmission();
delay(500);
}

#include <Wire.h>
void setup() {
 Wire.begin(9);
 Wire.onReceive(receiveEvent);
 Serial.begin(9600);
}
void loop() {
 delay(100);
}
void receiveEvent(int bytes) {
 while (Wire.available()) {
 char c = Wire.read();
 Serial.print("Received message: ");
 Serial.println(c);
 }
}