c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::write(unsigned char)': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/WiFiClient.cpp:215: multiple definition of `WiFiClient::write(unsigned char)'; libraries\WiFi\WiFiClient.cpp.o:C:\Program Files (x86)\Arduino\libraries\WiFi\src/WiFiClient.cpp:74: first defined here c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::peek()': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/WiFiClient.cpp:283: multiple definition of `WiFiClient::peek()'; libraries\WiFi\WiFiClient.cpp.o:C:\Program Files (x86)\Arduino\libraries\WiFi\src/WiFiClient.cpp:133: first defined here c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::connected()': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/WiFiClient.cpp:333: multiple definition of `WiFiClient::connected()'; libraries\WiFi\WiFiClient.cpp.o:C:\Program Files (x86)\Arduino\libraries\WiFi\src/WiFiClient.cpp:162: first defined here c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::operator bool()': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/WiFiClient.cpp:349: multiple definition of `WiFiClient::operator bool()'; libraries\WiFi\WiFiClient.cpp.o:C:\Program Files (x86)\Arduino\libraries\WiFi\src/WiFiClient.cpp:185: first defined here c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::connect(char const*, unsigned short)': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/WiFiClient.cpp:126: multiple definition of `WiFiClient::connect(char const*, unsigned short)'; libraries\WiFi\WiFiClient.cpp.o:C:\Program Files (x86)\Arduino\libraries\WiFi\src/WiFiClient.cpp:41: first defined here c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::available()': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/WiFiClient.cpp:256: multiple definition of `WiFiClient::available()'; libraries\WiFi\WiFiClient.cpp.o:C:\Program Files (x86)\Arduino\libraries\WiFi\src/WiFiClient.cpp:105: first defined here c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::write(unsigned char const*, unsigned int)': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/WiFiClient.cpp:220: multiple definition of `WiFiClient::write(unsigned char const*, unsigned int)'; libraries\WiFi\WiFiClient.cpp.o:C:\Program Files (x86)\Arduino\libraries\WiFi\src/WiFiClient.cpp:78: first defined here c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::read()': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/WiFiClient.cpp:269: multiple definition of `WiFiClient::read()'; libraries\WiFi\WiFiClient.cpp.o:C:\Program Files (x86)\Arduino\libraries\WiFi\src/WiFiClient.cpp:114: first defined here c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::read(unsigned char*, unsigned int)': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/WiFiClient.cpp:278: multiple definition of `WiFiClient::read(unsigned char*, unsigned int)'; libraries\WiFi\WiFiClient.cpp.o:C:\Program Files (x86)\Arduino\libraries\WiFi\src/WiFiClient.cpp:124: first defined here c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::WiFiClient()': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266/Print.h:45: multiple definition of `WiFiClient::WiFiClient()'; libraries\WiFi\WiFiClient.cpp.o:C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266/Print.h:45: first defined here c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::WiFiClient()': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266/Print.h:45: multiple definition of `WiFiClient::WiFiClient()'; libraries\WiFi\WiFiClient.cpp.o:C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\cores\esp8266/Print.h:45: first defined here c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::connect(IPAddress, unsigned short)': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/WiFiClient.cpp:141: multiple definition of `WiFiClient::connect(IPAddress, unsigned short)'; libraries\WiFi\WiFiClient.cpp.o:C:\Program Files (x86)\Arduino\libraries\WiFi\src/WiFiClient.cpp:50: first defined here c:/users/serge/appdata/local/arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/2.5.0-4-b40a506/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: libraries\ESP8266WiFi\ESP8266WiFi.a(WiFiClient.cpp.o): in function `WiFiClient::status()': C:\Users\Serge\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.6.3\libraries\ESP8266WiFi\src/WiFiClient.cpp:342: multiple definition of `WiFiClient::status()'; libraries\WiFi\WiFiClient.cpp.o:C:\Program Files (x86)\Arduino\libraries\WiFi\src/WiFiClient.cpp:176: first defined here collect2.exe: error: ld returned 1 exit status exit status 1 Error compiling for board NodeMCU 1.0 (ESP-12E Module).