CODEWITHSUNDEEP
nginxflasksocket.ioreverse-proxyflask-socketio
Qubasa
Qubasa

Reputation: 183

Socket.io + Flask and frontend HTTPS reverse proxy & backend HTTP reverse proxy

so my client websockets can't connect to the webserver if I try to reach the website over https. Over http it works. My setup is the following:

I have a python socketio webserver and a http reverse proxy (the backend proxy) locally on that machine that passes the requests through. This works quite well.

Now I have a frontend https reverse proxy that passes the connection to the backend, at this point it breaks. The websockets fail to connect now. If my fronted proxy uses http it works again.

Client error message:

The connection to wss://frontend.example.com/socket.io/?EIO=3&transport=websocket&sid=92f50dc52f374c79baca0ecfd14f15b6 was interrupted while the page was loading.

I use the flask-socketio library and start the python application with:

app = f.Flask(__name__)
socketio = sockio.SocketIO(app)
socketio.run(app)

$ netstat -tulpen
tcp        0      0 127.0.0.1:5000          0.0.0.0:*               LISTEN      1000       86048      5619/python3.7      
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      0          115411     6903/nginx: master

Backend nginx conf:

 server {
    listen 0.0.0.0:80 ;
    listen [::]:80 ;
    server_name backend.example.com ;
    location / {
            proxy_pass http://127.0.0.1:5000;

    }
    location /socket.io {
        proxy_pass http://127.0.0.1:5000;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection $connection_upgrade;
        proxy_set_header        Host $host;
        proxy_set_header        X-Real-IP $remote_addr;
        proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header        X-Forwarded-Proto $scheme;
        proxy_set_header        X-Forwarded-Host $host;
        proxy_set_header        X-Forwarded-Server $host;
        proxy_set_header        Accept-Encoding "";
    }
}

Frontend nginx conf:

server {
        listen 0.0.0.0:443 ssl http2 ;
        listen [::]:443 ssl http2 ;
        server_name frontend.example.com ;
        location /.well-known/acme-challenge {
                root /var/lib/acme/acme-challenge;
                auth_basic off;
        }
        ssl_certificate /var/lib/acme/frontend.example.com/fullchain.pem;
        ssl_certificate_key /var/lib/acme/frontend.example.com/key.pem;
        ssl_trusted_certificate /var/lib/acme/frontend.example.com/full.pem;
        location / {
                set $nix_proxy_target "http://backend.example.com";
                proxy_pass $nix_proxy_target;
        }
        location /socket.io {
                set $nix_proxy_target "http://backend.example.com";
                proxy_pass $nix_proxy_target;
                proxy_http_version 1.1;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection $connection_upgrade;
                proxy_set_header        Host $host;
                proxy_set_header        X-Real-IP $remote_addr;
                proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header        X-Forwarded-Proto $scheme;
                proxy_set_header        X-Forwarded-Host $host;
                proxy_set_header        X-Forwarded-Server $host;
                proxy_set_header        Accept-Encoding "";
        }
    }

Upvotes: 0

Views: 1154

Answers (1)

Qubasa
Qubasa

Reputation: 183

So I found out that the error was caused by socketio itself because of its cross origin policy which was not set to the correct url.

The solution was to add the following:

socketio = sockio.SocketIO(
    app, engineio_logger=DEBUG, cors_allowed_origins=["https://frontend.example.com"]
)

Upvotes: 0

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