Question in re remote.exec()

I have a question about remote.exec(). Let's say I have a user function, s1_1 that takes a BAT as a parameter and returns a BAT. Its signature might be:

function user.s1_1(in:bat[:oid,:int]):bat[:oid,:int];

How can I call s1_1 using remote.exec to pass in a BAT and to retrieve the result? I want to do something like

X_2 := remote.exec(conn, "user", "s1_1", X_1);

where X_1 and X_2 are both :bat[:oid,:int]. But that doesn't seem to work.

Thanks,

Steve Morgan