communications with a server

I have a question when I am testing with the web request blocks, my html 5 game must be uploaded to a server for it to work, the same with the multiplayer extension, because nothing works for me

That depends on so many factors. You really should be very exact what you are trying to do.
Most colyseus multiplayer examples run from your local computer to a server on the world wide web.
(ColyseusTickTacToe for instance)

To have us help you need to give error/warning messages. 'nothing works for me' is not very explanatory!

If you mean the visit url block then depending on the URL and the location of the files you might receive CORS message.

Check the console for these. (Right Mouse Click on Chrome, select Inspect and navigate to console output)
If you have CORS message you need special file on the server that allows navigation. Otherwise you can only access pages on the same server.