File transfer uses a direct peer-to-peer connection, which means that your computer and your friend's computer are connected directly to each other.
There are many reasons why this sort of connection may fail, including:
- The path between the two computers is incorrect.
- A failure in one of the routers between you and your friend.
- Your or your friend's computer is behind a firewall that is disrupting the connection.
You may want to check if either your or your friend's connection is restricted by a firewall.
