Can anybody explain this DBX error message?

[Tom Olin]

Configuration: Sun-4/150 and Sun-3/60; SunOS 4.0.3; GNU Emacs 18.52; X11R4.

I run Emacs within X11, and I use dbx within Emacs, either using dbx.el or
simply running dbx in the Emacs shell.  dbx works fine if I am running
Emacs on the same machine as the X server.  However, if I am running Emacs
remotely, dbx aborts immediately with the following message:

	dbx: fatal error: No such device or address

On the other hand, if I run a remote xterm (analogous to a sibling of
Emacs), dbx runs okay in the xterm.  Can anybody shed any light on this?