i found socket.io stop working on heroku.
Note: if you found you socket.io just stop working recently, this post may can help you!!
I found the reason in my case is:
I am using stack : heroku-16:
According to this:
heroku-16 is a docker image, which means it is a mini version of linux, it may been leaned too much, that's why our stocket.io stoped working.
I found the issue is fixed after I changed back to cedar-14: