Thanks,Bryan.
I ran the bokeh server with --log–level debug, and I got the logs as following:
PS C:\DeployTest> bokeh serve .\test1.py --allow-websocket-origin="*" --log-level debug
2021-06-24 08:16:58,304 Starting Bokeh server version 2.3.2 (running on Tornado 6.1)
2021-06-24 08:16:58,306 Host wildcard '*' will allow connections originating from multiple (or possibly all) hostnames or IPs. Use non-wildcard values to restrict access explicitly
2021-06-24 08:16:58,309 User authentication hooks NOT provided (default user enabled)
2021-06-24 08:16:58,309 These host origins can connect to the websocket: ['*']
2021-06-24 08:16:58,310 Patterns are:
2021-06-24 08:16:58,311 [('/test1/?',
2021-06-24 08:16:58,311 <class 'bokeh.server.views.doc_handler.DocHandler'>,
2021-06-24 08:16:58,311 {'application_context': <bokeh.server.contexts.ApplicationContext object at 0x0000017350ACAD00>,
2021-06-24 08:16:58,312 'bokeh_websocket_path': '/test1/ws'}),
2021-06-24 08:16:58,313 ('/test1/ws',
2021-06-24 08:16:58,313 <class 'bokeh.server.views.ws.WSHandler'>,
2021-06-24 08:16:58,313 {'application_context': <bokeh.server.contexts.ApplicationContext object at 0x0000017350ACAD00>,
2021-06-24 08:16:58,314 'bokeh_websocket_path': '/test1/ws',
2021-06-24 08:16:58,315 'compression_level': None,
2021-06-24 08:16:58,315 'mem_level': None}),
2021-06-24 08:16:58,315 ('/test1/metadata',
2021-06-24 08:16:58,316 <class 'bokeh.server.views.metadata_handler.MetadataHandler'>,
2021-06-24 08:16:58,316 {'application_context': <bokeh.server.contexts.ApplicationContext object at 0x0000017350ACAD00>,
2021-06-24 08:16:58,321 'bokeh_websocket_path': '/test1/ws'}),
2021-06-24 08:16:58,321 ('/test1/autoload.js',
2021-06-24 08:16:58,322 <class 'bokeh.server.views.autoload_js_handler.AutoloadJsHandler'>,
2021-06-24 08:16:58,322 {'application_context': <bokeh.server.contexts.ApplicationContext object at 0x0000017350ACAD00>,
2021-06-24 08:16:58,323 'bokeh_websocket_path': '/test1/ws'}),
2021-06-24 08:16:58,323 ('/?',
2021-06-24 08:16:58,324 <class 'bokeh.server.views.root_handler.RootHandler'>,
2021-06-24 08:16:58,324 {'applications': {'/test1': <bokeh.server.contexts.ApplicationContext object at 0x0000017350ACAD00>},
2021-06-24 08:16:58,325 'index': None,
2021-06-24 08:16:58,325 'prefix': '',
2021-06-24 08:16:58,325 'use_redirect': True}),
2021-06-24 08:16:58,325 ('/static/extensions/(.*)',
2021-06-24 08:16:58,325 <class 'bokeh.server.views.multi_root_static_handler.MultiRootStaticHandler'>,
2021-06-24 08:16:58,326 {'root': {}}),
2021-06-24 08:16:58,326 ('/static/(.*)',
2021-06-24 08:16:58,327 <class 'bokeh.server.views.static_handler.StaticHandler'>)]
2021-06-24 08:16:58,332 Bokeh app running at: http://localhost:5006/test1
2021-06-24 08:16:58,332 Starting Bokeh server with process id: 3612
2021-06-24 08:17:13,347 [pid 3612] 0 clients connected
2021-06-24 08:17:13,347 [pid 3612] /test1 has 14 sessions with 14 unused
2021-06-24 08:17:28,343 [pid 3612] 0 clients connected
2021-06-24 08:18:05,588 [pid 3612] /test1 has 14 sessions with 14 unused
2021-06-24 08:18:05,588 Scheduling 14 sessions to discard
2021-06-24 08:18:05,588 Discarding session 'VgYdmbP9gC2DC1F6om1vduyTjbfDJamD5WVeQDIK4bKb' last in use 63157.0 milliseconds ago
2021-06-24 08:18:05,588 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350AFD100>
2021-06-24 08:18:05,620 Discarding session 'P8gmEsjwjkeLi0RMbiBNjPaJK5tAqbyrilwddqAOR6tn' last in use 62969.0 milliseconds ago
2021-06-24 08:18:05,620 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B3B940>
2021-06-24 08:18:05,651 Discarding session '8y5utrQu1p5WwEvUJhpUhYo3iBcUu5yJ8VqxyArpXjGp' last in use 57922.0 milliseconds ago
2021-06-24 08:18:05,651 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B3B250>
2021-06-24 08:18:05,667 Discarding session 'kFfyDxgBSjVJO2zr0VCk5E3IE94eVtrhlRbsNa0daqIx' last in use 57703.0 milliseconds ago
2021-06-24 08:18:05,667 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B22F40>
2021-06-24 08:18:05,682 Discarding session 'TTEWARyOfTiArGkz7RHyX2OEvt4MNohtfEsMCybPWIM1' last in use 56640.0 milliseconds ago
2021-06-24 08:18:05,682 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B22820>
2021-06-24 08:18:05,698 Discarding session 'sc2FkTn5C1GEuRrFni8Ehukharyvh7G4OEMoRSN9opSQ' last in use 56484.0 milliseconds ago
2021-06-24 08:18:05,713 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B58610>
2021-06-24 08:18:05,729 Discarding session 'dCJLAiassrjmfeqWrt9xkwkWayWS5k3oIEfJJecSw82m' last in use 56172.0 milliseconds ago
2021-06-24 08:18:05,729 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B58CD0>
2021-06-24 08:18:05,760 Discarding session 'HmRO3fa2FMCEGzbXtjljSDuu5IGwdBel2qVER0cDaIVA' last in use 56016.0 milliseconds ago
2021-06-24 08:18:05,760 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B68400>
2021-06-24 08:18:05,792 Discarding session 'lcNbiysPjn1DQG9wmR09oe3ssO4thv1kAd1Vv8PvFZFX' last in use 55985.0 milliseconds ago
2021-06-24 08:18:05,792 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B68AC0>
2021-06-24 08:18:05,823 Discarding session 'VjvAeDsCec5771xvwfwtIaerE6Y1BlP6nq8KmwvF4BHn' last in use 55844.0 milliseconds ago
2021-06-24 08:18:05,823 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B761C0>
2021-06-24 08:18:05,854 Discarding session '4XqJa8hPcuLLRo5aijdBG2DS4VP9d8xxvllP85qnEIhY' last in use 55828.0 milliseconds ago
2021-06-24 08:18:05,854 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B76880>
2021-06-24 08:18:05,885 Discarding session '9qM5M5Imvq2kQuvWRJAOznjo8kQSz6cLRHxt2tHuUyva' last in use 55704.0 milliseconds ago
2021-06-24 08:18:05,885 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B76F40>
2021-06-24 08:18:05,901 Discarding session 'Txsb6qbqtqEfmFcMAvnJAgLvLOEVRvT77CbIEivzw1L3' last in use 55640.0 milliseconds ago
2021-06-24 08:18:05,901 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B84640>
2021-06-24 08:18:05,932 Discarding session 'qOxVcAmBsfdDWnU79YTc2CrhefUGCeY7vojzR91cosKU' last in use 55500.0 milliseconds ago
2021-06-24 08:18:05,932 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B84D00>
2021-06-24 08:18:13,340 [pid 3612] 0 clients connected
2021-06-24 08:18:13,340 [pid 3612] /test1 has 4 sessions with 4 unused
2021-06-24 08:18:23,354 Scheduling 4 sessions to discard
2021-06-24 08:18:57,121 Discarding session 'T9sr9Ltkb8V3pKsFxbwryoavM3DLgWPxskwaxgL2fazJ' last in use 51172.0 milliseconds ago
2021-06-24 08:18:57,121 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B84F40>
2021-06-24 08:18:57,152 Discarding session 'XUdgujq5V8HjI62gGsopRZIKK0tnhGOU8SST9DVW7OtE' last in use 51203.0 milliseconds ago
2021-06-24 08:18:57,152 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B84B80>
2021-06-24 08:18:57,183 Discarding session 'MImmkvT0yCgGHtfoZtIwUHdPUb2h1ppbRQXZXxQmI6Ma' last in use 51219.0 milliseconds ago
2021-06-24 08:18:57,183 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B58040>
2021-06-24 08:18:57,214 Discarding session 'rTNkOAd5SB16a3YH2M9EzjeP0nxjiGNtEmOn0oUWtnzh' last in use 50968.0 milliseconds ago
2021-06-24 08:18:57,214 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B58160>
2021-06-24 08:18:57,246 [pid 3612] 0 clients connected
2021-06-24 08:18:57,246 [pid 3612] /test1 has 2 sessions with 2 unused
2021-06-24 08:18:57,261 Scheduling 2 sessions to discard
2021-06-24 08:18:57,261 Discarding session 'wdMbbfjhqtrIuFME0WFqe9turPPq1E2LfkVjxDDMMwAG' last in use 40594.0 milliseconds ago
2021-06-24 08:18:57,261 Deleting 1 modules for <bokeh.document.document.Document object at 0x0000017350B3B070>
2021-06-24 08:18:57,277 Discarding session 'rTTuHctPmwC80Vt0vIrjvRBXHN6CyikNjv5J0ZDXQUuu' last in use 40360.0 milliseconds ago
2021-06-24 08:18:57,292 Deleting 1 modules for <bokeh.document.document.Document object at 0x00000173500E1820>
2021-06-24 08:18:58,339 [pid 3612] 0 clients connected
2021-06-24 08:18:58,339 [pid 3612] /test1 has 0 sessions with 0 unused
It seems like the client get connected to the apache, but not Bokeh(Tornado) server sit behind, just as you mentioned.