[BUG] Serve application at random port failed #10175
Description
Hello,
since Bokeh 2.1.0 (windows 10), trying to serve an application with random port (--port=0) does not work anymore and result in the following error:
(py37) D:\PythonWorkspace\divers>bokeh serve C:\Users\xa235208\Downloads\bokeh-master\examples\app\sliders.py --show --port=0
2020-06-16 09:39:45,845 Starting Bokeh server version 2.1.0 (running on Tornado 6.0.4)
2020-06-16 09:39:45,847 User authentication hooks NOT provided (default user enabled)
2020-06-16 09:39:45,850 Bokeh app running at: http://localhost:61622/sliders
2020-06-16 09:39:45,850 Starting Bokeh server with process id: 14652
2020-06-16 09:39:46,587 Refusing websocket connection from Origin 'http://localhost:61622'; use --allow-websocket-origin=localhost:61622 or set BOKEH_ALLOW_WS_ORIGIN=localhost:61622
to permit this; currently we allow origins {'localhost:0'}