Connect openems edge to a distant backend

1

Hello,

I’m trying to connect an openems edge device to and openems backend installed on a server out of the local network.
the server will works as a database and will be able to show the monitorig of edge devices
I’ve configured the server with nginx to make reverse proxy.

I can’t have a connexion between the edge device and the backend on the server.
i have the following error

2019-10-04 16:07:07,093 [read-493] INFO [socket.AbstractWebsocketClient] Websocket [ws://my_domain/openems-ws/] closed. Code [1002] Reason [Invalid status code received: 502 Status line: HTTP/1.1 502 Bad Gateway]

I have the following parameters on edge side

url : ws://my_domain/openems-ws/
proxy port 80

I have the followinf nginx config parapeters for websocket

  location /openems-ws/ {
  	proxy_http_version 1.1;
  	proxy_set_header Upgrade $http_upgrade;
  	proxy_set_header Connection "upgrade";

  	proxy_pass http://openems-ws/;
  	proxy_set_header Accept-Encoding "";

  	proxy_set_header Host $host;
  	proxy_set_header X-Real-IP $remote_addr;
  	proxy_set_header X-Forwarded-Host $host;
  	proxy_set_header X-Forwarded-Server $host;
  	proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  }

anyone has an idea of the problem?

2

Hello,

I’m not familiar with nginx but in my apache2 config I had to proxy pass to ws://127.0.0.1:8078 (the port that is set in the backend configuration)

I hope that helps.

3

How did you configure the edge application to connect to the backend?
can you show me your apache config for the reverse proxy?

It seems my backend websocket is not available even on localhost
I have the following message when I run an edge app on the same machine

[​c​t​r​l​B​a​c​k​e​n​d​0​]​ ​E​r​r​o​r​:​ ​C​o​n​n​e​c​t​i​o​n​ ​r​e​f​u​s​e​d​ ​(​C​o​n​n​e​c​t​i​o​n​ ​r​e​f​u​s​e​d​)

the backend is configured to open port 8081 for edge app

4

Hi,

what you want to do? a proxy pass you will only need, if you want to have a secure communication…

normally your websocket runs on a port like 8082 (default)

and than the config would be more like this

proxy_pass http://localhost:8082;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "Upgrade";

if it is on the same machine, else of course not localhost.

5

I forgot to show another config paramater

upstream openems-ws {
	server localhost:8081;
	keepalive 10;
}

so your config seems to be the same

6

Hi,

this is an example for a NGINX configuration that is quite similar to a productive system. It provides three endpoints

  • /m/ for UI
  • /openems-backend-ui for websocket connection from UI to Backend
  • /openems-backend for websocket connection from Edge to Backend

In this example, you would have to configure OpenEMS Edge Controller Api.Backend to the URL ws://mydomain.com/openems-backend.

server {
    server_name mydomain.com;
    listen 80 default;

    # OpenEMS-UI
    location /m/ {
        alias /opt/openems-ui/;
        index index.html;
        try_files $uri$args $uri$args/ /m/index.html;
    }

    # Proxy for OpenEMS UI -> OpenEMS Backend
    location /openems-backend-ui {
        proxy_pass http://localhost:8092;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        keepalive_timeout 120s;
        proxy_connect_timeout 120s;
        proxy_read_timeout 36000s;
        proxy_send_timeout 36000s;
    }

    # Proxy for OpenEMS Edge -> OpenEMS Backend
    location /openems-backend {
        proxy_pass http://localhost:8091;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        keepalive_timeout 120s;
        proxy_connect_timeout 120s;
        proxy_read_timeout 36000s;
        proxy_send_timeout 36000s;
    }
}

Hope that helps.
Regards.