LwIP and .CPP file extension

There is a list of some errors founded...

*** [Core_Final.elf] Error 1 Core_Final

obj/apps/base.o *../apps/echo.cpp:222: undefined reference to `tcp_accept(tcp_pcb*, signed char (*)(void*, tcp_pcb*, signed char))' In function `con_erro':

obj/apps/base.o *../apps/base.cpp:314: undefined reference to `tcp_sent(tcp_pcb*, signed char (*)(void*, tcp_pcb*, unsigned short))'

../apps/base.cpp:315: undefined reference to `tcp_recv(tcp_pcb*, signed char (*)(void*, tcp_pcb*, pbuf*, signed char))'

obj/apps/base.o *../apps/base.cpp:315: undefined reference to `tcp_recv(tcp_pcb*, signed char (*)(void*, tcp_pcb*, pbuf*, signed char))'

../apps/base.cpp:316: undefined reference to `mem_free(void*)'

obj/apps/base.o *../apps/base.cpp:316: undefined reference to `mem_free(void*)'

../apps/base.cpp:317: undefined reference to `tcp_close(tcp_pcb*)'

obj/apps/base.o *../apps/base.cpp:317: undefined reference to `tcp_close

Best Regards,

Nosima