You can try to close the port and see if delivery optimisation works to make sure this is created by windows service only.
Delivery Optimization listens on port 7680 for requests from other peers by using TCP/IP. The service will register and open this port on the device. The port must be set to accept inbound traffic through your firewall. If you don't allow inbound traffic over port 7680, you can't use the peer-to-peer functionality of Delivery Optimization.
Hope this resolves your Query !!
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