Acct and Auth on single port

Is it possible to have both accounting a authorization requests on a single port? I have a bit of legacy equipment that has a single configuration option for radius port, and appears to send both the account and authorization packets to whatever port is defined there. I have tried created two listen directives both using the same port and listing auth in one and acct in the other, with no success. Is there some method to making this work, or am I stuck with just not getting accounting from this device? Thanks -- Jon M