opengl programming from Windows to Unix

I am trying to write a program in Unix and I keep getting a runtime error saying "GLUT: Fatal Error in myProgram: cannot open display." I wrote the exact same code in Windows Visual C++ and it runs perfectly. Is there something that I am missing? If anyone has had this problem, or know what to do, I could really use your help.

[rts]

There isn't nearly enough information here to really be able to help you... the problem could be anything from a misconfigured X session to "xhost + localhost".

Post more info. What's your X config. like? What does "glinfo" and "glxinfo" say? Can you get the Mesa demos to work (e.g. "gears")? Anything suspicious in your code? Distro? Kernel version? XFree86 version? ... ?