I added port and server of a remote FitNesse instance as variables (we have quite a few FitNesse installations). These don't get resolved. Following the stack trace

13:11:49 hudson.plugins.fitnesse.FitnesseBuilder: {fitnesseTargetPage=FrontPage.SmokeTests, fitnesseTargetIsSuite=true, fitnesseHost=${FitNesse_hostname}, fitnesseHttpTimeout=7200000, fitnessePortRemote=, fitnesseStart=False, fitnessePathToXmlResultsOut=fitnesse-results.xml}
13:11:49 Connnecting to http://${FitNesse_hostname}/FrontPage.SmokeTests?suite&format=xml
13:11:49 java.net.UnknownHostException: ${FitNesse_hostname}
13:11:49 at java.net.PlainSocketImpl.connect(Unknown Source)
13:11:49 at java.net.SocksSocketImpl.connect(Unknown Source)
13:11:49 at java.net.Socket.connect(Unknown Source)
13:11:49 at java.net.Socket.connect(Unknown Source)
13:11:49 at sun.net.NetworkClient.doConnect(Unknown Source)
13:11:49 at sun.net.www.http.HttpClient.openServer(Unknown Source)
13:11:49 at sun.net.www.http.HttpClient.openServer(Unknown Source)
13:11:49 at sun.net.www.http.HttpClient.<init>(Unknown Source)
13:11:49 at sun.net.www.http.HttpClient.New(Unknown Source)
13:11:49 at sun.net.www.http.HttpClient.New(Unknown Source)
13:11:49 at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
13:11:49 at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
13:11:49 at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
13:11:49 at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
13:11:49 at java.net.HttpURLConnection.getResponseCode(Unknown Source)
13:11:49 at hudson.plugins.fitnesse.FitnesseExecutor.getHttpBytes(FitnesseExecutor.java:218)
13:11:49 at hudson.plugins.fitnesse.FitnesseExecutor$1.run(FitnesseExecutor.java:197)
13:11:49 at java.lang.Thread.run(Unknown Source)
13:11:49 Xml results saved as windows-1252 to D:\Hudson\jobs\OCNS_Test_FitNesse\workspace\fitnesse-results.xml