static S invokeEcjInFirstVM(File optionsFile) {
  if (dontUsePort5000()) fail("Not using port 5000");
  DialogIO io = talkTo("localhost", 5000);
  if (startsWith(io.readLine(), "This is a JavaX VM")) {
    S answer = io.ask(format("invoke ecj on options file *", f2s(optionsFile)));
    //print(answer);
    new Matches m;
    if (swic(answer, "OK ", m)) ret cleanJavaCompilerOutput($1);
    fail(answer);
  }
  fail("No VM at port 5000");
}