Nginx not proxying websockets (using socket.io and nodejs) - node.js

Question

I have a nodejs application running on port 8000 and the following nginx configs to proxy my requests (8800 for http and 8443 for https):
http {
include mime.types;
default_type application/octet-stream;
sendfile on;
keepalive_timeout 65;
gzip on;
upstream node {
server 127.0.0.1:8000;
}
map $http_upgrade $connection_upgrade {
default upgrade;
'' close;
}
server {
listen 8800;
access_log /usr/local/etc/nginx/access.log;
error_log /usr/local/etc/nginx/error.log;
rewrite_log on;
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_set_header X-NginX-Proxy true;
proxy_pass http://node;
proxy_redirect off;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection $connection_upgrade;
}
}
server {
listen 8443;
ssl on;
ssl_certificate /usr/local/etc/nginx/server.crt;
ssl_certificate_key /usr/local/etc/nginx/server.key;
ssl_session_timeout 5m;
ssl_protocols SSLv2 SSLv3 TLSv1;
ssl_ciphers HIGH:!aNULL:!MD5;
ssl_prefer_server_ciphers on;
access_log /usr/local/etc/nginx/access.log;
error_log /usr/local/etc/nginx/error.log;
rewrite_log on;
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_set_header X-NginX-Proxy true;
proxy_pass http://node;
proxy_redirect off;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection $connection_upgrade;
}
}
}
When I try to run my application at http://localhost:8800 and check Chrome Dev Tools, the websocket request (ws://localhost) returns a successful '101 Switching protocols'. But the same request (wss://localhost) doesn't work when I run it on the https://localhost (with self certified SSL certs)
Also, when I try to debug the request on nginx with
curl -i -N -H "Connection: Upgrade" -H "Upgrade: websocket" http://localhost:8800/
or
curl -i -N -k -H "Connection: Upgrade" -H "Upgrade: websocket" https://localhost:8443/
the response is 502 Bad Gateway.
I am trying to figure out why nginx isn't proxying the request properly.