error reference with header files

I am writing a TCP client and server pair of programs to play around with sending string back and forth.
My program is I am having trouble making the compiler refernece the function prototypes in a header file
and the implemented souce file when I use the modulated code with the server and client.

TCPEchoServer.c:(.text+0x92): undefined reference to `dieWithError'
TCPEchoServer.c:(.text+0x18a): undefined reference to `handleTCPClient'

Thank you all