Jruby --ng-server fails trying to bind to a specific port (2113)

I’m trying to use JRuby’s nailgun
I can’t seem to get the thing to start up for me:

klauer@klauer-imac ~
$ jruby --ng-server &
[1] 31219

klauer@klauer-imac ~
$ NGServer started on, port 2113.
java.net.BindException: Can’t assign requested address
at java.net.PlainSocketImpl.socketBind(Native Method)
at java.net.PlainSocketImpl.bind(PlainSocketImpl.java:383)
at java.net.ServerSocket.bind(ServerSocket.java:328)
at java.net.ServerSocket.(ServerSocket.java:194)
at com.martiansoftware.nailgun.NGServer.run(Unknown Source)
at java.lang.Thread.run(Thread.java:680)
com.martiansoftware.nailgun.builtins.NGAlias: 0/0
com.martiansoftware.nailgun.builtins.NGClasspath: 0/0
com.martiansoftware.nailgun.builtins.NGServerStats: 0/0
com.martiansoftware.nailgun.builtins.NGStop: 0/0
com.martiansoftware.nailgun.builtins.NGVersion: 0/0
NGServer shut down.

I’m not sure why I’m getting this, but I know for a fact that port 2113
not open, as I can’t find any tcp/udp port open at all on my Mac:

netstat -nlp tcp
netstat -nlp udp

Any tips for troubleshooting this? Is there a way to specify a
port altogether to rule out some errant process hogging port 2113 on my

-Nick K.