This executes a shell command in Scala and returns the actual server IP instead of 127.0.0.1 or the domain name of the host. #| is used to simulate piping of commands. Process and Seq are used for awk as $NF will lead to compilation errors otherwise.
The actual shell command is: ip route get 8.8.8.8 | awk '{print $NF; exit}'
import scala.sys.process._
val addr = ("ip route get 8.8.8.8" #| Process(Seq("awk", "{print $NF; exit}"))).!!.trim
val port = System.getProperty("http.port", "9000")
[UPDATE 08 APR 2017]
A friend pointed out that the shell command could have been replaced by hostname --all-ip-addresses. This is preferred to hostname -i as the latter may return 127.0.0.1 and is not recommended in the manual as it requires resolution of the hostname.