public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { if ("upgrade".equals(req.getHeader("Upgrade"))) { res.setStatus(101); res.setHeader( "X-Powered-By", "Servlet/3.1 " + "(GlassFish Server Open Source Edition 4.0 Java/Oracle Corporation/1.7)"); res.setHeader("Upgrade", "upgrade"); res.setHeader("Connection", "Upgrade"); res.flushBuffer(); System.out.println("Upgrade OK " + req.getHeader("Upgrade")); MyHttpUpgradeHandler handler = req.upgrade(MyHttpUpgradeHandler.class); } else { System.out.println("No upgrade: "); } }