File transfer problem with Smack4 and OpenFire 3.93

My team is developing an Android chat application.

The sender is on a wifi network, the recipient is on the same wifi network.

OpenFire is on a separate network that is publicly accessible.

My file transfers always error out at the initial or the negotiating stage.

Here is my outgoing packet from the sender phone:

drawinghttp://jabber.org/protocol/ibb

And the error from OpenFire:

2014.06.12 13:32:03 org.jivesoftware.openfire.IQRouter - Packet sent to unreachable address drawinghttp://jabber.org/protocol/ibb

After weeks of going back and forth, we seemingly have solved the problem by:

Replacing the default resource of /Smack with /Android when sending files, and

Disabled proxy service on the OpenFire server

I hope this will help other users.