b.option(ChannelOption.SO_KEEPALIVE, true);
b.remoteAddress(HOST, PORT);
b.handler(initializer);
// Start the client.
Channel channel = b.connect().syncUninterruptibly().channel();
System.out.println("Connected to [" + HOST + ':' + PORT + ']');
// Wait for the HTTP/2 upgrade to occur.
Http2SettingsHandler http2SettingsHandler = initializer.settingsHandler();
http2SettingsHandler.awaitSettings(5, TimeUnit.SECONDS);