The Sonos Port does not have an optical out.

I see, I assumed 1 was in and the other was out.  Looks like RCA to 3.5mm

Setting this up not so difficult. You could try a Bluetooth transmitter like this with coaxial in and out. Connect it to your port and the coaxial out from transmitter to your Denon. 

Where it becomes tricky, if you want the Bluetooth audio to be in sync with your Sonos? Bluetooth has some latency/delay man people can hear, even if using low latency Bluetooth. 

Here’s the back of the Port. You can use the Digital output for your Denon and the RCA out for your headphones.

Your Denon also may have an RCA output you could use with a bluetooth transmitter.

I don’t think the device @Marcellus H. recomends would work as it’s a bluetooth receiver, not a transmitter (also no coax output).  But there are plenty of transmitters available you can find on Amazon and elsewhere. 

The Port with the coax out is for playing sonos in that room through my Denon 7.2 system. If I put the transmitter on the RCA out will I be able to get sound through that for my headphones?  They are also for sonos music only. I play a lot of zones throughout my home and having a sync issue would be unacceptable.

Sorry, you right! The device I linked in my first post is NOT a transmitter. This one is, or whatever other suitable transmitter... 

Should work. Your Denon may already have a built in bluetooth transmitter, did you check?

BUT: I am sorry to say, I highly doubt that bt headphones will play in sync for you, because of the latency that comes with bluetooth. Multiple audio streams with over 30ms delay most people perceive as separated, but maybe it works for you. Sony bt cans used to come with cables, so you can use wired playback as backup solution...

If I am wearing the headphones I won’t need to worry about syncing with other zones.  I didn’t check to see if the Denon has a transmitter but when listening through the Heaphones the Denon will be turned off.  The Port will just be sort of an extra zone within the one unit.  Waiting for SONOS to bring the rumored headphones to market has taken too long for me to wait any longer.

Thanks for your help.

Tim

The headphone latency issue would come into play when you are trying to match audio with video.  Since streaming audio via Sonos is the source, that’s not likely to be a concern.

If I want to use them while watching TV, I can pair them (Sony WH-1000XM5) with my Sony Bravia, I am sure they match up well.  When I play music all around the house I sometimes drive my wife crazy so that is why the sudden urge for headphones..  Happy Wife / Happy Life.