Perfetto, partiamo con ordine:
questo è il mio sketch modificato a seguito del tuo suggerimento:
#include <SPI.h>
#include <Ethernet.h>
// Enter a MAC address for your controller below.
// Newer Ethernet shields have a MAC address printed on a sticker on the shield
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
// if you don't want to use DNS (and reduce your sketch size)
// use the numeric IP instead of the name for the server:
IPAddress server(192,168,1,80); // numeric IP for Google (no DNS)
//char server[] = "www.google.com"; // name address for Google (using DNS)
// Set the static IP address to use if the DHCP fails to assign
IPAddress ip(192, 168, 0, 177);
IPAddress myDns(192, 168, 0, 1);
// Initialize the Ethernet client library
// with the IP address and port of the server
// that you want to connect to (port 80 is default for HTTP):
EthernetClient client;
unsigned long byteCount = 0;
bool printWebData = true; // set to false for better speed measurement
void setup() {
// 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 connection:
Serial.println("Initialize Ethernet with DHCP:");
if (Ethernet.begin(mac) == 0) {
Serial.println("Failed to configure Ethernet using DHCP");
// 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(1); // do nothing, no point running without Ethernet hardware
}
}
if (Ethernet.linkStatus() == LinkOFF) {
Serial.println("Ethernet cable is not connected.");
}
// try to congifure using IP address instead of DHCP:
Ethernet.begin(mac, ip, myDns);
} else {
Serial.print(" DHCP assigned IP ");
Serial.println(Ethernet.localIP());
}
// give the Ethernet shield a second to initialize:
delay(1000);
Serial.print("connecting to ");
Serial.print(server);
Serial.println("...");
// if you get a connection, report back via serial:
int retcode = client.connect(server, 80);
if (retcode) {
Serial.print("connected to ");
Serial.println(client.remoteIP());
// Make a HTTP request:
client.println("GET /esempio.php?Username=Arduino HTTP/1.1");
client.println("Host: 192.168.1.80");
client.println("Connection: close");
client.println();
client.println();
} else {
// if you didn't get a connection to the server:
Serial.print("connection failed (");
Serial.print(retcode);
Serial.println(")");
}
}
void loop() {
int len = client.available();
if (len > 0) {
byte buffer[80];
if (len > 80) len = 80;
client.read(buffer, len);
if (printWebData) {
Serial.write(buffer, len); // show in the serial monitor (slows some boards)
}
byteCount = byteCount + len;
}
// if the server's disconnected, stop the client:
if (!client.connected()) {
Serial.println();
Serial.println("disconnecting.");
client.stop();
// do nothing forevermore:
while (true) {
delay(1);
}
}
}
l'output su monitor seriale che mi viene dato è:
Initialize Ethernet with DHCP:
DHCP assigned IP 192.168.1.107
connecting to 192.168.1.80...
connection failed (0)
disconnecting.
Lo scrip d'esempio che ho usato è questo:
#include <SPI.h>
#include <Ethernet.h>
// Enter a MAC address for your controller below.
// Newer Ethernet shields have a MAC address printed on a sticker on the shield
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
// if you don't want to use DNS (and reduce your sketch size)
// use the numeric IP instead of the name for the server:
IPAddress server(74,125,232,128); // numeric IP for Google (no DNS)
//char server[] = "www.google.com"; // name address for Google (using DNS)
// Set the static IP address to use if the DHCP fails to assign
IPAddress ip(192, 168, 0, 177);
IPAddress myDns(192, 168, 0, 1);
// Initialize the Ethernet client library
// with the IP address and port of the server
// that you want to connect to (port 80 is default for HTTP):
EthernetClient client;
// Variables to measure the speed
unsigned long beginMicros, endMicros;
unsigned long byteCount = 0;
bool printWebData = true; // set to false for better speed measurement
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
// 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 connection:
Serial.println("Initialize Ethernet with DHCP:");
if (Ethernet.begin(mac) == 0) {
Serial.println("Failed to configure Ethernet using DHCP");
// 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(1); // do nothing, no point running without Ethernet hardware
}
}
if (Ethernet.linkStatus() == LinkOFF) {
Serial.println("Ethernet cable is not connected.");
}
// try to congifure using IP address instead of DHCP:
Ethernet.begin(mac, ip, myDns);
} else {
Serial.print(" DHCP assigned IP ");
Serial.println(Ethernet.localIP());
}
// give the Ethernet shield a second to initialize:
delay(1000);
Serial.print("connecting to ");
Serial.print(server);
Serial.println("...");
// if you get a connection, report back via serial:
if (client.connect(server, 80)) {
Serial.print("connected to ");
Serial.println(client.remoteIP());
// Make a HTTP request:
client.println("GET /search?q=arduino HTTP/1.1");
client.println("Host: www.google.com");
client.println("Connection: close");
client.println();
} else {
// if you didn't get a connection to the server:
Serial.println("connection failed");
}
beginMicros = micros();
}
void loop() {
// if there are incoming bytes available
// from the server, read them and print them:
int len = client.available();
if (len > 0) {
byte buffer[80];
if (len > 80) len = 80;
client.read(buffer, len);
if (printWebData) {
Serial.write(buffer, len); // show in the serial monitor (slows some boards)
}
byteCount = byteCount + len;
}
// if the server's disconnected, stop the client:
if (!client.connected()) {
endMicros = micros();
Serial.println();
Serial.println("disconnecting.");
client.stop();
Serial.print("Received ");
Serial.print(byteCount);
Serial.print(" bytes in ");
float seconds = (float)(endMicros - beginMicros) / 1000000.0;
Serial.print(seconds, 4);
float rate = (float)byteCount / seconds / 1000.0;
Serial.print(", rate = ");
Serial.print(rate);
Serial.print(" kbytes/second");
Serial.println();
// do nothing forevermore:
while (true) {
delay(1);
}
}
}
Ed ho appena notato che effettivamente il server non si disconnette mai, continua a stamparmi cose su monitor seriale, cioè non entra mai nell'
if (!client.connected())
.
Ho catturato con uno screenshoot le prime informazioni stampate perché è impossibile fare copia incolla:
connected to 74.125.232.128
HTTP/1.1 200 OK
Content-Type: text/html; charset=ISO-8859-1
Date: Tue, 31 Mar 2020 12:00:02 GMT
Expires: -1
Cache-Control: private, max-age=0
P3P:CP="This is not a P3P policy! See g.co/p3phelp for more info."
Server: gws
X-XSS-Protection: 0
X-Frame-Options: SAMEORIGIN
Set-Cookie: IP_JAR=2020-03-31-12; expires=Thu, 30-Apr-2020 12:00:002 GMT; path=/; domain=.google.com; Secure
...
...
Volevo allegare direttamente qui lo screen, non è possibile hostare immagini sul forum? 
Non è che magari hai un firewall sul tuo Linux (che distro e versione?) che blocca le connessioni esterne (es. iptables)?
Attualmente sto usando un pc con Windwos 10 come Server, quindi escludo possa essere un problema di firewall, e poi in ogni caso essendo una comunicazione in locale potrebbero comunque esserci problemi di firewall?
