A recent JPRT build showed this failure on windows_i586_6,2-product build:

[CLIENT] Exception caught: java.io.IOException: Could not connect to server
java.io.IOException: Could not connect to server
at com.sun.tools.sjavac.client.SjavacClient.tryConnect(SjavacClient.java:183)
at com.sun.tools.sjavac.client.SjavacClient.compile(SjavacClient.java:126)
at com.sun.tools.sjavac.client.ClientMain.run(ClientMain.java:84)
at com.sun.tools.sjavac.client.ClientMain.run(ClientMain.java:47)
at com.sun.tools.sjavac.Main.go(Main.java:56)
at com.sun.tools.sjavac.Main.main(Main.java:46)
A rerun of the job successfully built the target.