Any advice regarding porting from windows to Linux

[nabilchampion]

Hi all
I am assigned a task which is to port a windows project into linux. I am relatively new to the porting concept. However I find this as interesting. But to my wonder I don’t see much discussion or help on porting at web and forums. Usually people try to port an application to linux by using WINE but I think that it is not actual porting of the application but instead we are running a windows executable inside linux process through some virtual layer… but that is not porting as much as I have understood. Also to write a portable code is not as difficult as to try to port an existing Windows specific application code into the linux platform.
I have a windows application/project built in C/C++ using windows API and MFC at some spots. Now the application need to be ported to Linux. I want to understand that are there any rules & guidelines specific to the porting. Currently I have situation somewhat like this:
Application has a MS COM Component depending on various libraries present in the shape of DLLs.
This COM (Component Object Model) serves the basic and fundamental logic of the application. But it uses several other 3rd party libraries and some self built libraries present in the form of DLL. Some of these DLLs are using MFC library.

Can any body suggest me that what formula I shall apply and follow any theory of porting in my situation. Currently I am planning to try to convert all the DLLs in a Linux Dynamic shared library and exclude all the MFC/Win API specific part from the code(that can be analyzed later). But What I have confliction is that is there any replacement of MS COM technology in Linux or I have to convert that COM into the Shared Library as well such that a separate process is forked in linux which contain a shared object or some thing like that. I really need the expert programmers guidance and any kind of information will be appreciated.
Regards

[nabilchampion]

:m enjoying many replies here

[likwid]

AFAIK you'd just have to look at what the specific winapi function is doing, and find a comparable posix function or functions. I worked with a guy who helped port a big server application that accessed hardware also, from windows to linux. He just went through and changed the winapi stuff to posix or linux functions.

[nga_tom]

Two schools of thought on porting. One says this is an opportunity to rearchitect the application (I have yet to meet an app that could not stand some improvement in this area) and the other says it works just move it.
I personally think a port is a time to revisit the original requirements and see if they are still valid and if things need to be added/deleted. On the architecture front, is there good seperation between business logic, database access and front end? Is exception handling/error logging adequate? Can scability be improved? Can performance be improved (better code not a bigger box with with more memory and procs)? How are things from a security perspective (sql injection and buffer overflows as well as user roles and permissions)?
Moving GUI functionality will be a three ring circus - linux is a little short in the widget and controls department and trying to duplicate that functionality can prove more than interesting.
Good Luck
tom