How to fix issue "Real-time connection lost" in Version 18 ?

🔍 The Problem

If you're running Odoo 18 and suddenly see the dreaded (especially in Discuss):

“Real-time connection lost”

...you might assume it's a network glitch, but it's often caused by Odoo's WebSocket-based bus system not being correctly proxied — especially when you're running behind NGINX.

🧠 Root Cause

Odoo 18 uses WebSockets (via gevent) to power its real-time features such as:

• Chat
• Notifications
• Live status indicators
• Bus communication

If WebSocket connections are not upgraded and routed correctly, the client fails to stay connected — hence the "Real-time connection lost" message.

🧪 Symptoms I Saw

• The message shows frequently in the web UI.
• Real-time updates (chat, bus events) don’t work.
• Logs show connection resets or 400/403 on /websocket.

🛠️ The Fix:

Step 1: Enable gevent with a dedicated port in odoo.conf

[options]
proxy_mode = True
gevent_port = 8072

Odoo uses this port to handle WebSocket traffic via gevent workers, normally it is 8072.

Step 2: Add a WebSocket location block in your NGINX config

upstream odoochat {
    server 127.0.0.1:20018;  # Your Odoo longpolling port
}

location /websocket {
    proxy_pass http://odoochat;

    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "Upgrade";
    proxy_set_header X-Forwarded-Host $http_host;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_set_header X-Real-IP $remote_addr;

    # Optional: Force HTTPS Strict Transport Security
    add_header Strict-Transport-Security "max-age=31536000; includeSubDomains";
}

This block tells NGINX to upgrade the connection from HTTP to WebSocket using the proper headers. Without this, Odoo's frontend won't stay connected to the backend event bus.

🚀 Result

✅ Real-time features work again

✅ No more connection lost messages

✅ Chat and live events are stable

✅ All handled via config — no code changes

🧠 Final Notes

• If you're using Docker, be sure to expose both Odoo’s HTTP and WebSocket ports.
• If you're behind Cloudflare or another CDN, make sure they allow WebSocket connections to your backend. 
  

🙌 This is a summary of my investigation and solution to the "Real-time connection lost" issue in Odoo 18 Community Edition. After testing and refining the configuration, the problem was resolved successfully.

One of the most helpful resources I came across during this process was a discussion on the Odoo Forum titled: Error (Real-time connection lost) Odoo 18 Community