Tcomport is very good for a free component and,I use Tcomport with delphi without any problem,I think that with "Builder" it's the same.
Otherwise you can use "Asyncpro" he is free now
The official site seems to have disappeared. You can get it from
**broken link removed**
-who wrote the C++ Builder port for this excellent library. I have used it with Builder 6 and it works, though there is a slightly tricky process to install it. This is described in the files.
It works with Windows XP when programmed with C++ Builder 6.
I would expect that it would work with Delphi since the library itself is delphi based (as well the the entire visual component library (VCL) of C++ Builder).
The project is now part of sourceforge and has been ported to Delphi 7 as well.