Send and Receive UDP String

This sketch waits for a UDP packet on a local port. When a valid packet is 
received, an acknowledge packet is sent back to client on a specified 
outgoing port.
LAST REVISION: 10/05/2022, 08:00 AM

This sketch waits for a UDP packet on a local port. When a valid packet is 
received, an acknowledge packet is sent back to client on a specified 
outgoing port.

Hardware Required
	Arduino WiFi Shield
	Shield-compatible Arduino board

Circuit
The WiFi shield uses pins 10, 11, 12, and 13 for SPI connection to 
HDG104 module. Digital pin 4 is used to control chip select pin on SD 
card.
You should have access to a 802.11b/g wireless network that connects to 
internet for this example. You will need to change network settings in 
sketch to correspond to your particular networks SSID.


WiFiShield bb

image developed using Fritzing. For more circuit examples, see Fritzing 
project page
In above image, Arduino board would be stacked below WiFi shield.
Code

/*H*******************************************************
WiFi UDP Send and Receive String
This sketch wait an UDP packet on localPort using a WiFi shield.
When a packet is received an Acknowledge packet is sent to client on port remotePort
Circuit:
* WiFi shield attached
created 30 December 2012
by dlf (Metodo2 srl)
********************************************************/
#include 
#include 
#include 

//************************* DEFINES ************************************

//************************* PROTOTYPES ************************************
void printWifiStatus(); 

//************************* VARIABLES ************************************
int status = WL_IDLE_STATUS;
char ssid[] = "yourNetwork";                         //  NETWORK SSID (NAME)
char pass[] = "secretPassword";// NETWORK PASSWORD (FOR WPA, OR AS KEY FOR WEP)
int keyIndex = 0;          // NETWORK KEY INDEX NUMBER (NEEDED ONLY FOR WEP)
unsigned int localPort = 2390;                    // LOCAL PORT TO LISTEN ON
char packetBuffer[255];                            // INCOMING PACKET BUFFER 
char  ReplyBuffer[] = "acknowledged";                     // RESPONSE STRING 
WiFiUDP Udp;

/*F********************************************************************
*
**********************************************************************/
void 
setup() 
{
	Serial.begin( BAUD );           // INIT SERIAL AND WAIT FOR PORT TO OPEN
	while( !Serial ) 
	{
		;// WAIT FOR SERIAL PORT TO CONNECT. NEEDED FOR NATIVE USB PORT ONLY
	}
	if( WiFi.status() == WL_NO_SHIELD )      // CHECK FOR PRESENCE OF SHIELD
	{
		Serial.println( "WiFi shield not present" );
		while( true );                                     // DON'T CONTINUE
	}
	String fv = WiFi.firmwareVersion();
	if( fv != "1.1.0" ) 
		Serial.println("Please upgrade firmware");
	while( status != WL_CONNECTED )    // ATTEMPT TO CONNECT TO Wifi NETWORK
	{
		Serial.print( "Attempting to connect to SSID: ");
		Serial.println( ssid );
// CONNECT TO WPA/WPA2 NETWORK. cHANGE THIS LINE IF USING OPEN OR WEP NETWORK
		status = WiFi.begin( ssid );
		delay( 10000 );                    // WAIT 10 SECONDS FOR CONNECTION
	}
	Serial.println( "Connected to wifi" );
	printWifiStatus();
	Serial.println("\nStarting connection to server...");
	// if you get a connection, report back via serial:
	Udp.begin(localPort);
}
/*F********************************************************************
*
**********************************************************************/
void 
loop() 
{
	int packetSize = Udp.parsePacket();
	if( packetSize )              // IF THERE'S DATA AVAILABLE, READ A PACKE
	{
		Serial.print( "Received packet of size ");
		Serial.println( packetSize);
		Serial.print( "From ");
		IPAddress remoteIp = Udp.remoteIP();
		Serial.print( remoteIp);
		Serial.print( ", port ");
		Serial.println( Udp.remotePort());
		int len = Udp.read( packetBuffer, 255 );  // READ PACKET INTO BUFFFER
		if( len > 0 ) 
			packetBuffer[len] = 0;
		Serial.println("Contents:");
		Serial.println(packetBuffer);
		// SEND A REPLY, TO IP ADDRESS AND PORT THAT SENT US PACKET RECEIVED
		Udp.beginPacket( Udp.remoteIP(), Udp.remotePort());
		Udp.write( ReplyBuffer );
		Udp.endPacket();
	}
}
/*F********************************************************************
*
**********************************************************************/
void 
printWifiStatus() 
{
	Serial.print("SSID: ");             // PRINT SSID OF NETWORK ATTACHED TO
	Serial.println(WiFi.SSID());
	IPAddress ip = WiFi.localIP();
	Serial.print( "IP Address: ");
	Serial.println( ip );                          // PRINT WiFi SHIELD'S IP
	long rssi = WiFi.RSSI();
	Serial.print( "signal strength (RSSI):");
	Serial.print( rssi );                  // PRINT RECEIVED SIGNAL STRENGTH
	Serial.println( " dBm" );
}