Details
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Bug
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Resolution: Duplicate
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Not Evaluated
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None
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6.5.1
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None
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Emscripten 3.1.25. Qt v6.5.1 for Linux Desktop (Debian Bookworm) x64.
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WebAssembly
Description
Using the "WebSockets MQTT Subscription Example" compiled to a WebAssembly target the "Sec-WebSocket-Protocol" is missing from the list of headers. Tested against a Mosquitto broker which ignores the client when the subprotocol is not set correctly. Wireshark trace shows that it is missing from the WASM target. The response message "Switching Protocols" doesn't contain the subprotocol header so the communication fails to continue correctly.
Compiling the same exact code for C++ works as expected.
https://doc.qt.io/qt-6/qtmqtt-websocketsubscription-example.html
Note: I hard-coded the default command line options for my setup.
WASM target from Wireshark for initial WebSocket connection:
Hypertext Transfer Protocol GET / HTTP/1.1\r\n Host: 10.101.30.101:9001\r\n Connection: Upgrade\r\n Pragma: no-cache\r\n Cache-Control: no-cache\r\n User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36\r\n Upgrade: websocket\r\n Origin: http://localhost:8080\r\n Sec-WebSocket-Version: 13\r\n Accept-Encoding: gzip, deflate\r\n Accept-Language: en-US,en;q=0.9\r\n Sec-WebSocket-Key: 3x3wFkBbMUcr42Q4mH4bww==\r\n Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits\r\n \r\n [Full request URI: http://10.101.30.101:9001/] [HTTP request 1/1] [Response in frame: 886]
C++ target for initial WebSocket connection:
Hypertext Transfer Protocol
GET / HTTP/1.1\r\n
Host: 10.101.30.101:9001\r\n
Upgrade: websocket\r\n
Connection: Upgrade\r\n
Sec-WebSocket-Key: MTjWOjycHIQ8o9NiYZoZcA==\r\n
Sec-WebSocket-Version: 13\r\n
Sec-WebSocket-Protocol: mqttv3.1\r\n
\r\n
[Full request URI: http://10.101.30.101:9001/]
[HTTP request 1/1]
[Response in frame: 90]
Mosquitto configuration file:
listener 9001
protocol websockets
allow_anonymous true