static long dm_evalOnOtherMachineWithReturnValue_timeout = 60000;

sO dm_evalOnOtherMachineWithReturnValue(fS computerID, S code, O... _) {

  fS id = aGlobalID();

  final new Var<Either<O, S>> var;

  temp vmBus_onMessage('gotFromPrivateChat, voidfunc(S sender, S msg) {

    if (var.has() || neq(sender, computerID)) ret;

    new Matches m;

    if (!startsWith(msg, "done " + id + " ", m)) ret;

    if (neq(getAuthorOfSignedText(msg), computerID)) {

      File f = javaxCachesDir("failed-eval-msg-" + computerID);

      saveTextFile(f, msg);

      var.set((Either) eitherB("eval result from " + computerID + " did not verify, saved as " + f));

    }

    S s = firstLine(m.rest());

    if (startsWith(s, "direct: ", m))

      var.set((Either) eitherA(m.rest()));

    else if (startsWith(s, "quoted: ", m))

      var.set((Either) eitherA(unquote(m.rest())));

    else if (startsWith(s, "base64: ", m))

      var.set((Either) eitherA(base64decode(m.rest())));

    else if (startsWith(s, "error: ", m))

      var.set((Either) eitherB(m.rest()));

    else

      var.set((Either) eitherB("unknown mode"));

  });

  dm_privateChat_sendSigned(computerID, computerID + " eval "

    + (boolOptPar(_, 'realEval) ? "real " : "")

    + (boolOptPar(_, 'fresh) ? "fresh " : "")

    + id + ": " + code);

  Either<O, S> e = waitForVarToBeNotNullWithTimeout(var, dm_evalOnOtherMachineWithReturnValue_timeout);

  if (boolPar updateControllableFlag(_))

    dm_pcall('controllableComputerList, 'setControllableByMe, computerID, eitherIsA(e));

  if (e == null) fail("timeout");

  if (eitherIsB(e)) fail(eitherGetB(e));

  ret eitherGetA(e);

}