Improve Ethernet initialization and diagnostics

Added hardware presence and link status checks to Ethernet initialization. Enhanced error messages for failed configurations and included gateway and subnet information in successful initialization logs. Also added Ethernet.maintain() in loop to support DHCP lease maintenance and link status monitoring.

Author: dorkmo

TankAlarm-112025-Server-BluesOpta/TankAlarm-112025-Server-BluesOpta.ino

@@ -21,7 +21,12 @@
 #include <Wire.h>
 #include <ArduinoJson.h>
 #include <Notecard.h>
-#include <Ethernet.h>
+#if defined(ARDUINO_OPTA) || defined(ARDUINO_PORTENTA_H7_M7) || defined(ARDUINO_PORTENTA_H7_M4)
+  #include <PortentaEthernet.h>
+  #include <Ethernet.h>
+#else
+  #include <Ethernet.h>
+#endif
 #include <math.h>
 #include <string.h>
 #include <ctype.h>
@@ -2578,6 +2583,9 @@ void loop() {
   IWatchdog.reload();
 #endif
 
+  // Maintain DHCP lease and check link status
+  Ethernet.maintain();
+
   handleWebRequests();
 
   unsigned long now = millis();
@@ -2879,6 +2887,16 @@ static void scheduleNextViewerSummary() {
 
 static void initializeEthernet() {
   Serial.print(F("Initializing Ethernet..."));
+  
+  // Check if Ethernet hardware is present
+  if (Ethernet.hardwareStatus() == EthernetNoHardware) {
+    Serial.println(F(" FAILED - No Ethernet hardware detected!"));
+    Serial.println(F("ERROR: Cannot continue without Ethernet. Please check hardware."));
+    while (true) {
+      delay(1000);
+    }
+  }
+  
   int status;
   if (gConfig.useStaticIp) {
     status = Ethernet.begin(gMacAddress, gStaticIp, gStaticDns, gStaticGateway, gStaticSubnet);
@@ -2887,11 +2905,29 @@ static void initializeEthernet() {
   }
 
   if (status == 0) {
-    Serial.println(F(" failed"));
+    Serial.println(F(" FAILED - Could not configure Ethernet!"));
+    if (!gConfig.useStaticIp) {
+      Serial.println(F("ERROR: DHCP failed. Check network cable and DHCP server."));
+    } else {
+      Serial.println(F("ERROR: Static IP configuration failed."));
+    }
+    while (true) {
+      delay(1000);
+    }
+  }
+  
+  // Check link status
+  if (Ethernet.linkStatus() == LinkOFF) {
+    Serial.println(F(" WARNING - No network cable connected!"));
+    Serial.println(F("Continuing, but web server will not be accessible."));
   } else {
     Serial.println(F(" ok"));
     Serial.print(F("IP Address: "));
     Serial.println(Ethernet.localIP());
+    Serial.print(F("Gateway: "));
+    Serial.println(Ethernet.gatewayIP());
+    Serial.print(F("Subnet: "));
+    Serial.println(Ethernet.subnetMask());
   }
 }