This is what my setup looks like:

INTERNET (subdomain.domain.com A Record to public IP 186....187)
Hurl.it -----POST-----> Public IP: https://186....187/API/switches?sw1?password=123456 -----> Linksys Router IP:186...187:443 Port Forward to 192...53

ONLAN (nginx setup https with ssl from letsencrypt)
192....53 RPi2 nginx config bypass 192...53:442 . ------> nodejs app.js listening on port 442

This is my nginx config file:

[code]
server {
listen 443 ssl;
listen [::]:443 ssl;
server_name subdomain.domain.com;

ssl_certificate /etc/letsencrypt/live/subdomain.domain.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/subdomain.domain.com/privkey.pem;

root /www/subdomain.domain.com/aism;
index index.php index.html index.htm;

error_page 404 /404.html;
error_page 500 502 503 504 /50x.html;

# Error & Access logs
error_log /www/subdomain.domain.com/logs/error.log error;
access_log /www/subdomain.domain.com/logs/access.log;

location / {
index index.html index.php;
proxy_pass http://192.168.1.53:442;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
location ~ /.well-known {
allow all;
}
location /public {
root /www/subdomain.domain.com/aism;
}
location ~ ^/(images/|img/|javascript/|js/|css/|stylesheets/|flash/|media/|static/) {
}
}[/code]

I have tested the nodejs app while on port 80 from hurl.it with the port forward config for port 80 instead and it works perfectly.

Here is the current error log:

[quote]
OST /API/switches/sw1?password=123456 HTTP/1.1", upstream: "http://192.168.1.53:442/50x.html", host: "subdomain.domain.com"
2017/04/23 20:08:38 [error] 20424#0: *4 upstream prematurely closed connection while reading response header from upstream, client: 192.168.1.56, server: subdomain.domain.com, request: "GET /aism/ HTTP/1.1", upstream: "http://192.168.1.53:442/aism/", host: "subdomain.domain.com"
2017/04/23 20:08:38 [error] 20424#0: *4 upstream prematurely closed connection while reading response header from upstream, client: 192.168.1.56, server: subdomain.domain.com, request: "GET /aism/ HTTP/1.1", upstream: "http://192.168.1.53:442/50x.html", host: "subdomain.domain.com"
2017/04/23 20:09:25 [error] 20467#0: *1 upstream prematurely closed connection while reading response header from upstream, client: 23.20.198.108, server: subdomain.domain.com, request: "POST /API/switches/sw1?password=123456 HTTP/1.1", upstream: "http://192.168.1.53:442/API/switches/sw1?password=123456", host: "subdomain.domain.com"
[/code]

Please help!