Be sure to set the following notes.ini params for the plugin to load properly:
XPagesPreload=1 
XPagesPreloadDB=websocket.nsf



xockets.io as of 2.0.1
-Fixed a problem with the plugin importing to the designer client (indirect reference to unneeded plugin removed)
-Updated the logic for message durability to save an inbound message during the onMessage method instead of during the send.
-(NOT TESTED YET) Added native transport settings WEBSOCKET_NATIVE_TRANSPORT for Linux based systems only (reduces memory consumption and GC overhead)
-Refactored NettyTestClient to use main method invocation so the loaded websocket clients stay loaded throughout the entire test.
-Refactored some of the notes api java operations for performance (e.g. use unid instead of view lookup where possible)
-Updated Config object to be based off an interface for easier substitutions during testing.
-Updated some netty calls to reduce memory overhead and GC
-(NOT TESTED) Removed the XPage 9.0.1 plugin references.  This might allow the websocket plugin to function in 8.5.3