jQuery AJAX to node server throws net::ERR_CONNECTION_REFUSED

Question

I have disabled my firewall (ufw on Ubuntu 15.04 server). This seems to be the most common cause of this problem.

Additionally some people have problems using AJAX,

Answer 1

data: JSON.stringify(testdata),

That's probably your problem. You need to serialize your json object. And you need to set the .ajax call to type of POST in options otherwise it will default to a get.