Radiohead library communication

Question

I am newbie, please bear me :)

I am following this client server example of RadioHead found in its library, http://www.airspayce.com/mikem/arduino/RadioHead/ I used Dragino Lora Shield with Arduino Uno and Arduino Mega. I have few questions if someone can help me:

1) I do not see server or client address so how server and clients are sending messages? 2) We can see code "while (!Serial) ;", Is it sending and receiving data by usb serial, not by wireless radio signals

Server

// rf95_server.pde
// -*- mode: C++ -*-
// Example sketch showing how to create a simple messageing server
// with the RH_RF95 class. RH_RF95 class does not provide for addressing or
// reliability, so you should only use RH_RF95  if you do not need the higher
// level messaging abilities.
// It is designed to work with the other example rf95_client
// Tested with Anarduino MiniWirelessLoRa, Rocket Scream Mini Ultra Pro with
// the RFM95W, Adafruit Feather M0 with RFM95

#include <SPI.h>
#include <RH_RF95.h>

// Singleton instance of the radio driver
RH_RF95 rf95;
//RH_RF95 rf95(5, 2); // Rocket Scream Mini Ultra Pro with the RFM95W
//RH_RF95 rf95(8, 3); // Adafruit Feather M0 with RFM95 

// Need this on Arduino Zero with SerialUSB port (eg RocketScream Mini Ultra Pro)
//#define Serial SerialUSB

int led = 9;

void setup() 
{
  // Rocket Scream Mini Ultra Pro with the RFM95W only:
  // Ensure serial flash is not interfering with radio communication on SPI bus
//  pinMode(4, OUTPUT);
//  digitalWrite(4, HIGH);

  pinMode(led, OUTPUT);     
  Serial.begin(9600);
  while (!Serial) ; // Wait for serial port to be available
  if (!rf95.init())
    Serial.println("init failed");  
  // Defaults after init are 434.0MHz, 13dBm, Bw = 125 kHz, Cr = 4/5, Sf = 128chips/symbol, CRC on

  // The default transmitter power is 13dBm, using PA_BOOST.
  // If you are using RFM95/96/97/98 modules which uses the PA_BOOST transmitter pin, then 
  // you can set transmitter powers from 5 to 23 dBm:
//  driver.setTxPower(23, false);
  // If you are using Modtronix inAir4 or inAir9,or any other module which uses the
  // transmitter RFO pins and not the PA_BOOST pins
  // then you can configure the power transmitter power for -1 to 14 dBm and with useRFO true. 
  // Failure to do that will result in extremely low transmit powers.
//  driver.setTxPower(14, true);
}

void loop()
{
  if (rf95.available())
  {
    // Should be a message for us now   
    uint8_t buf[RH_RF95_MAX_MESSAGE_LEN];
    uint8_t len = sizeof(buf);
    if (rf95.recv(buf, &len))
    {
      digitalWrite(led, HIGH);
//      RH_RF95::printBuffer("request: ", buf, len);
      Serial.print("got request: ");
      Serial.println((char*)buf);
//      Serial.print("RSSI: ");
//      Serial.println(rf95.lastRssi(), DEC);
      
      // Send a reply
      uint8_t data[] = "And hello back to you";
      rf95.send(data, sizeof(data));
      rf95.waitPacketSent();
      Serial.println("Sent a reply");
       digitalWrite(led, LOW);
    }
    else
    {
      Serial.println("recv failed");
    }
  }
}

Client

// rf95_client.pde
// -*- mode: C++ -*-
// Example sketch showing how to create a simple messageing client
// with the RH_RF95 class. RH_RF95 class does not provide for addressing or
// reliability, so you should only use RH_RF95 if you do not need the higher
// level messaging abilities.
// It is designed to work with the other example rf95_server
// Tested with Anarduino MiniWirelessLoRa, Rocket Scream Mini Ultra Pro with
// the RFM95W, Adafruit Feather M0 with RFM95

#include <SPI.h>
#include <RH_RF95.h>

// Singleton instance of the radio driver
RH_RF95 rf95;
//RH_RF95 rf95(5, 2); // Rocket Scream Mini Ultra Pro with the RFM95W
//RH_RF95 rf95(8, 3); // Adafruit Feather M0 with RFM95 

// Need this on Arduino Zero with SerialUSB port (eg RocketScream Mini Ultra Pro)
//#define Serial SerialUSB

void setup() 
{
  // Rocket Scream Mini Ultra Pro with the RFM95W only:
  // Ensure serial flash is not interfering with radio communication on SPI bus
//  pinMode(4, OUTPUT);
//  digitalWrite(4, HIGH);

  Serial.begin(9600);
  while (!Serial) ; // Wait for serial port to be available
  if (!rf95.init())
    Serial.println("init failed");
  // Defaults after init are 434.0MHz, 13dBm, Bw = 125 kHz, Cr = 4/5, Sf = 128chips/symbol, CRC on

  // The default transmitter power is 13dBm, using PA_BOOST.
  // If you are using RFM95/96/97/98 modules which uses the PA_BOOST transmitter pin, then 
  // you can set transmitter powers from 5 to 23 dBm:
//  driver.setTxPower(23, false);
  // If you are using Modtronix inAir4 or inAir9,or any other module which uses the
  // transmitter RFO pins and not the PA_BOOST pins
  // then you can configure the power transmitter power for -1 to 14 dBm and with useRFO true. 
  // Failure to do that will result in extremely low transmit powers.
//  driver.setTxPower(14, true);
}

void loop()
{
  Serial.println("Sending to rf95_server");
  // Send a message to rf95_server
  uint8_t data[] = "Hello World!";
  rf95.send(data, sizeof(data));
  
  rf95.waitPacketSent();
  // Now wait for a reply
  uint8_t buf[RH_RF95_MAX_MESSAGE_LEN];
  uint8_t len = sizeof(buf);

  if (rf95.waitAvailableTimeout(3000))
  { 
    // Should be a reply message for us now   
    if (rf95.recv(buf, &len))
   {
      Serial.print("got reply: ");
      Serial.println((char*)buf);
//      Serial.print("RSSI: ");
//      Serial.println(rf95.lastRssi(), DEC);    
    }
    else
    {
      Serial.println("recv failed");
    }
  }
  else
  {
    Serial.println("No reply, is rf95_server running?");
  }
  delay(400);
}

Answer 1

1) I do not see server or client address so how server and clients are sending messages?

1. Lora is a radio protocol that any receiver is able to decode (as long as they have the Semtech chip or equivalent). Like receiving FM radio - all you need is an antenna and the will to do it. :)

   LoraWAN is a network specification with Lora transmission as its physical layer. LoraWAN specifies facilities for end-to-end encryption of packets, device addressing, replay attack protection, congestion management, channel hopping, application provisioning, etc.

2) We can see code "while (!Serial) ;", Is it sending and receiving data by usb serial, not by wireless radio signals

2. The RadioHead libraries do not interact with Serial or redirect it in any way.

   while (!Serial); is a standard Arduino idiom. The Serial class implements a method operator bool() such that (bool)Serial evaluates to true when it is ready to use. Thus, while (!Serial); is a tight loop that waits until the Serial port is ready.