We have vast experience in developing such systems , implementing various protocols over RS232, RS 485 , Ethernet and WiFi and we can definitely be of assistance to you in this project.
Even though you have described the salient features, I think the requirement will have to be refined, because it looks like some factors have not been considered.
For example, you are talking about sending a file across over serial port to a terminal. This ma be a test case and may be there is another device/computer receives this file. Have you considered the case of errors occurring over serial port? When you dump a file to a terminal the data will simply scroll off the screen and there may not be much use of it. It is ok for testing a concept, but may not be suitable for a properly designed solution
Can we discuss more on these issues , in which we have a lot to contribute
Thanks