How to handle independent request and response

Hi all,
Here I have scenario where communication happens with files. My asp.net application builds request as a plain text and save as a txt file and place it on a server. Then I shall be getting response as a plain text which is saved in a txt file and placed on the same server. Now I need to pick this file and process. As request and response are two independent tasks how to acheive this kind of communication? After placing request how could I wait and check for response file? Here communication happens over files only. Please suggest.