Quote Originally Posted by aash_89 View Post
undefined reference to '_imp__ZN10QTcpSocketC1EP7QObject'
That's a linker error. It means that it can't find a certain function or class in the libraries it has access to (or knows about).

Why you get this error is not easy to answer with the explanation you gave. So please post your complete code, including your .pro file and explain exactly how you build your code. Are you using Qt Creator for example?