The Address field contains the base address on which this listen socket is listening. A host can have multiple network interfaces and multiple IP addresses. The address contains the IP address and the port number.
If your listen socket listens on all network interfaces for the host machine, the IP part of the address is 0.0.0.0.
This setting is tunable when you edit an HTTP listener. If you specify an IP address other than 0.0.0.0, the server makes one less system call per connection. Specify an IP address other than 0.0.0.0 for best possible performance.