Official guide

I encountered some errors while following the Official guide.
Lucky, I fixed all the errors and make it work finally.
Notes my workaround here, hope it work for you if you have the same problem.

gpg: keyserver receive failed: keyserver error

local install guide

solution from stackoverflow

sudo apt-key adv --keyserver hkp://keys.gnupg.net:80 --recv-keys 5AFA7A83

WebSocket connection to 'wss://<local_ip>:8433/kurento' failed: Error in connection establishment: net::ERR_CONNECTION_REFUSED

cause

the application server is started with https if you follow the guide:

http-server -p 8443 -S -C keys/server.crt -K keys/server.key

but kurento media server start without ssl by default config.
You can get from the config and the default port is 8888.
/etc/kurento/kurento.conf.json

solution

modify kurento media server config to enable ssl and use the same cert that used for your application server. it is a little complex.
but we have a easy solution, just start your application without ssl and test with firefox(if use chrome, you will got a dom exception, then you have to enable ssl for kms).

modify js/index.js
ws_uri: 'ws://' + location.hostname + ':8888/kurento'

start application server with
http-server -p 8443

record callback not triggered

if you use kurento-hello-world-recorder-generator as the example, then everything works well.
but if you use kurento-tutorial-js/kurento-recorder, you might found record not work.

https://github.com/Kurento/kurento-tutorial-js/pull/3

Below patch is work solution for it, but it was not accepted, strange thing.
https://github.com/Kurento/kurento-tutorial-js/pull/3/commits/ccab45818f3336639eec3c02a56f14209124901c