As part of fixing an existing bug Oracle introduced a new bug into FilterOutputStream.close:
While the bug is marked as fixed the fix will not be available until Java 9 from what I can tell and is not in the latest release as of writing (1.8.91)
This bug can also be reproduced through remote socket closure.
Due to this bug the TelnetClient when calling disconnect() throws an unhandled exception and is unable to close the connection, if the socket was remotely closed.
java.net.SocketException: Socket closed