i have try explain below:

1. application1 create A1 file and write some text to A1 file.
application1 running windows server

2. application2 download A1 file from windows server to unix server.
application2 running unix server

problem is application1 writing text to A1 file(not finish) and this time try download application2 file A1.

application2 did download not complete A1 file.