Suggestion on RSEINB00 ( file to idoc)

Hi,

What is the use of port in program RSEINB00. How does the program identifies to which idoc it has to convert the flat file.

Should we maintain any control record in the header of the flat file.If yes can anybody give me the format of the file which RSEINB00 identifies.

Will I be maintain a remote location for flat file in program RSEINB00 through FTP connection or the file has to from application server itself.

Thanks & Regards,

Karthik.k