Broken pipe error

Errors in error log, but all work and users don’t report about problems. What this means?

2015.12.07 10:10:18 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 10:13:55 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 10:16:05 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 10:32:05 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 10:47:18 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 10:53:56 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 11:12:20 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 11:27:02 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 13:13:22 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 13:32:47 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 13:37:16 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 13:39:09 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 13:40:38 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 13:56:58 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 14:07:11 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 14:08:00 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 14:08:42 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe
2015.12.07 14:18:16 org.jivesoftware.openfire.net.SocketConnection - Failed to deliver stream close tag: Broken pipe

Ubuntu server 14.04.3 x64 openfire 3.10.3.

This message indicates a sever-to-server (S2S) network connection was terminated before the corresponding XMPP stream was properly closed. This is a benign error condition that does not directly affect any users and should not appear in the error log. Starting with the next release this message will appear in the debug log only.