WebSocket handshake fails in Chrome due to missing Sec-WebSocket-Protocol field

[triska]

Steps to reproduce:

1. Start the echo server that is shown in the documentation of library(http/websocket), using:

   ?- http_server(http_dispatch, [port(8090)]).
   

2. Use the following JavaScript line to establish a WebSocket connection in Chrome:

   var s = new WebSocket("ws://localhost:8090/ws", "protocolOne");
   

Chrome refuses the connection with:

Error during WebSocket handshake: Sent non-empty 'Sec-WebSocket-Protocol' header but no response was received

If possible, please add this header field to the response. Thank you!