make WiFi/Ethernet interface compatible with Arduino Ethernet API (#8645)

* make WiFi/Ethernet interface compatible with Arduino Ethernet API
provide some minimaly adapted examples from legacy

* move ethernet compat globals to EthernetCompat.h

* LegacyEthernet: add UDP example

* adjust comments

Co-authored-by: Max Prokhorov <prokhorov.max@outlook.com>

libraries/lwIP_Ethernet/examples/LegacyUDPSendReceiveString/LegacyUDPSendReceiveString.ino

@@ -0,0 +1,156 @@
+/*
+ UDPSendReceiveString:
+ This sketch receives UDP message strings, prints them to the serial port
+ and sends an "acknowledge" string back to the sender
+
+ A Processing sketch is included at the end of file that can be used to send
+ and received messages for testing with a computer.
+
+ Circuit:
+ * Ethernet Wiznet5500/Wiznet5100/ENC28J60 on esp8266
+
+ created 21 Aug 2010
+ by Michael Margolis
+
+ This code is in the public domain.
+ */
+
+// specific to esp8266 w/lwIP
+#include <EthernetCompat.h>
+ArduinoWiznet5500lwIP Ethernet(/*SS*/ 16);  // <== adapt to your hardware
+// ArduinoWiznet5100lwIP Ethernet(/*SS*/ 16);  // <== adapt to your hardware
+// ArduinoENC28J60lwIP Ethernet(/*SS*/ 16);  // <== adapt to your hardware
+
+// Enter a MAC address for your controller below.
+// Newer Ethernet shields have a MAC address printed on a sticker on the shield
+byte notNeededButAllowed_mac[] = {
+  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED
+};
+byte* mac = nullptr;  // automatic mac
+IPAddress ip(192, 168, 1, 177);
+
+unsigned int localPort = 8888;  // local port to listen on
+
+// buffers for receiving and sending data
+char packetBuffer[UDP_TX_PACKET_MAX_SIZE];  // buffer to hold incoming packet,
+char ReplyBuffer[] = "acknowledged";        // a string to send back
+
+// An EthernetUDP instance to let us send and receive packets over UDP
+EthernetUDP Udp;
+
+void setup() {
+  // You can use Ethernet.init(pin) to configure the CS pin
+  // Ethernet.init(10);  // Most Arduino shields
+  // Ethernet.init(5);   // MKR ETH shield
+  // Ethernet.init(0);   // Teensy 2.0
+  // Ethernet.init(20);  // Teensy++ 2.0
+  // Ethernet.init(15);  // ESP8266 with Adafruit Featherwing Ethernet
+  // Ethernet.init(33);  // ESP32 with Adafruit Featherwing Ethernet
+  //                    // esp8266 w/lwIP: SS set in Ethernet constructor
+
+  // Open serial communications and wait for port to open:
+  Serial.begin(9600);
+  while (!Serial) {
+    ;  // wait for serial port to connect. Needed for native USB port only
+  }
+
+  // start the Ethernet
+  // Ethernet.begin(mac, ip);
+  if (Ethernet.begin(mac) == 0) {
+    Serial.println("Failed to configure Ethernet using DHCP");
+    while (true) {
+      delay(1000);  // do nothing, no point running without Ethernet hardware
+    }
+  }
+
+  // Check for Ethernet hardware present
+  if (Ethernet.hardwareStatus() == EthernetNoHardware) {
+    Serial.println("Ethernet shield was not found.  Sorry, can't run without hardware. :(");
+    while (true) {
+      delay(1000);  // do nothing, no point running without Ethernet hardware
+    }
+  }
+  if (Ethernet.linkStatus() == LinkOFF) {
+    Serial.println("Ethernet cable is not connected.");
+  }
+
+  Serial.println("Started and waiting");
+  Serial.print("IP Address: ");
+  Serial.println(Ethernet.localIP());
+  Serial.print("UDP port: ");
+  Serial.println(localPort);
+
+  // start UDP
+  Udp.begin(localPort);
+}
+
+void loop() {
+  // if there's data available, read a packet
+  int packetSize = Udp.parsePacket();
+  if (packetSize) {
+    Serial.print("Received packet of size ");
+    Serial.println(packetSize);
+    Serial.print("From ");
+    IPAddress remote = Udp.remoteIP();
+    for (int i = 0; i < 4; i++) {
+      Serial.print(remote[i], DEC);
+      if (i < 3) {
+        Serial.print(".");
+      }
+    }
+    Serial.print(", port ");
+    Serial.println(Udp.remotePort());
+
+    // read the packet into packetBufffer
+    Udp.read(packetBuffer, UDP_TX_PACKET_MAX_SIZE);
+    Serial.println("Contents:");
+    Serial.println(packetBuffer);
+
+    // send a reply to the IP address and port that sent us the packet we received
+    Udp.beginPacket(Udp.remoteIP(), Udp.remotePort());
+    Udp.write(ReplyBuffer);
+    Udp.endPacket();
+  }
+  delay(10);
+}
+
+
+/*
+  Processing sketch to run with this example
+ =====================================================
+
+ // Processing UDP example to send and receive string data from Arduino
+ // press any key to send the "Hello Arduino" message
+
+
+ import hypermedia.net.*;
+
+ UDP udp;  // define the UDP object
+
+
+ void setup() {
+ udp = new UDP( this, 6000 );  // create a new datagram connection on port 6000
+ //udp.log( true ); 		// <-- printout the connection activity
+ udp.listen( true );           // and wait for incoming message
+ }
+
+ void draw()
+ {
+ }
+
+ void keyPressed() {
+ String ip       = "192.168.1.177";	// the remote IP address
+ int port        = 8888;		// the destination port
+
+ udp.send("Hello World", ip, port );   // the message to send
+
+ }
+
+ void receive( byte[] data ) { 			// <-- default handler
+ //void receive( byte[] data, String ip, int port ) {	// <-- extended handler
+
+ for(int i=0; i < data.length; i++)
+ print(char(data[i]));
+ println();
+ }
+ */