Sharing files between 2 Amazon AWS instances

This is not intuitive at all, and moreover, I found only 1 post that indicated how to do this. The idea is to open the following ports between the instances:

• Microsoft file sharing SMB: User Datagram Protocol (UDP) ports from 135 through 139 and Transmission Control Protocol (TCP) ports from 135 through 139.
• Direct-hosted SMB traffic without a network basic input/output system (NetBIOS): port 445 (TCP and UPD).

After this, you should be good to go. I got this information from this post, or you can go to this KB article from Microsoft as well.