Microsoft Edge Websockets: "SCRIPT12030" error after 30secs

Question

I am developing an Angular 5 Application, which talks to the Server (IoT Device) over a Websocket connection, where JSON-messages are sent and also received.

The application works fine on Firefox, Chrome and Opera - but with Microsoft Edge, the connection closes after an idle time of 30sec with the following error message:

SCRIPT12030: WebSocket Error: Network Error 12030, The connection with the server was terminated abnormally

Additional information:

• IoT-Device is in LAN, so no Proxy is used
• Connection closes after 30sec of inactivity on the websocket connection
• There is no difference, if i use "ws://" or "wss://"
• The other parts of the Angular applications work normal
• Version of Edge is 40.15063.674.0, EdgeHTML 15.15063

How can i keep the connection open?

Answer 1

Microsoft Edge sends "Pong"-messages - even if their was no "Ping"-Message before.

The IoT-Device could not parse the "Pong"-message and closed the websocket connection.

Other browser only respond with "Pong"-messages, if their was a "Ping"-message before. As solution we implemented Ping/Pong-in our IoT-Device.