Known support
  Browser:
    See: http://caniuse.com/#search=websocket
    For non websocket-aware browsers you can use https://github.com/gimite/web-socket-js/ , "HTML5 Web Socket implementation powered by Flash".
  Server:
    node-xmpp-bosh

References
  XMPP:
    http://xmpp.org/rfcs/rfc6120.html RFC 6120 - XML streams, SASL, TLS, stanza semantics 
    http://xmpp.org/rfcs/rfc6121.html RFC 6121 - XMPP extensions for basic instant messaging and presence
    http://xmpp.org/rfcs/rfc6122.html RFC 6122 - XMPP address format
    http://xmpp.org/xmpp-protocols/xmpp-extensions/
  WebSocket:
    http://dev.w3.org/html5/websockets/
  XMPP over WebSocket:
    https://tools.ietf.org/html/draft-moffitt-xmpp-over-websocket-00

    http://blog.superfeedr.com/xmpp-over-websockets/

Similar/related software
  Server-side:
    https://code.google.com/p/node-xmpp-bosh/ (a websocket/bosh proxy)
    https://github.com/superfeedr/ejabberd-websockets (a module that adds websocket support to ejabberd)
    https://code.google.com/p/prosody-modules/wiki/mod_websocket (a module that adds websocket support to prosody)
  Client-side:
    https://github.com/superfeedr/strophejs/tree/protocol-ed (a websocket-aware fork of strophejs)