server.properties only has fields for:

server-port

server-portv6

However, when bedrock server is run, four ports appear to be opened per server. 

Additionally, this prevents multiple instances of bedrock_server.exe from being run on the same OS because IP's can't be properly deconflicted. If two instances are run (in their own folders with their own server.properties specifying unique IPv4 and IPv6 ports), only one instance will actually work.

The hack to make a second instance work (on windows) is to rename the bedrock_server.exe to something else such as bedrock_server_1.exe. Then multiple instances work ... sometimes.

This is probably a function of the Windows firewall not knowing which running instance of bedrock_server.exe to route inbound traffic to.