Fix ESP8266 KNX unwanted reply (#24267)

CHANGELOG.md

@@ -18,6 +18,7 @@ All notable changes to this project will be documented in this file.
 - ESP32 BLE not starting (#24240)
 - GDK101 power on detection (#24242)
 - Udisplay backlight with SPI displays (#24277)
+- ESP8266 KNX unwanted reply (#24267)
 
 ### Removed
 

RELEASENOTES.md

@@ -127,6 +127,7 @@ The latter links can be used for OTA upgrades too like ``OtaUrl https://ota.tasm
 
 ### Fixed
 - ESP8266 TasmotaSerial flush receive buffer on executing `TasmotaSerial.flush();`
+- ESP8266 KNX unwanted reply [#24267](https://github.com/arendst/Tasmota/issues/24267)
 - ESP32-P4 unique MQTT Client based on hosted MCU MAC address
 - GDK101 power on detection [#24242](https://github.com/arendst/Tasmota/issues/24242)
 - Udisplay backlight with SPI displays [#24277](https://github.com/arendst/Tasmota/issues/24277)

lib/lib_div/esp-knx-ip-0.5.2/src/esp-knx-ip.cpp

@@ -558,7 +558,11 @@ void ESPKNXIP::__loop_knx()
 
   DEBUG_PRINTLN(F(""));
 
+#ifdef ESP8266
+  while (udp.available()) { udp.read(); }  // ESP8266 does endPacket() on flush() which in turn does send() which is NOT what we want
+#else
   udp.flush();
+#endif
 
   knx_ip_pkt_t *knx_pkt = (knx_ip_pkt_t *)buf;