how can I implement pixel tracker in NodeJs

Question

I implement NodeJS api from what user can send multiple emails to multiple contacts (nodemailer), I want to track open rate, I test this from my localhost by inserting 1px image in html body with src call for server route : <img src="http://1xx.xxx.x.xx:4001/v1/users/google-tracker"/> but nothing happen in my server side when I open mail, no call for this route !!! anybody have an idea about the problem ? is it google who's blocking that ??