The function close-remote-debugging-connection performs all the close cleanup operations that were associated with connection by remote-debugging-connection-add-close-cleanup, closes the underlying stream and clears any other resources that connection is using.
close-remote-debugging-connection may be called on either side (IDE or client) and causes the other side of the connection to call close-remote-debugging-connection on its own side.
close-remote-debugging-connection is called automatically by LispWorks when the other side closes the connection. It is also called automatically after you call configure-remote-debugging-spec with :setup-default nil when the Debugger or Remote Listener window is closed.
During debugging, you probably do not need to worry about closing connections, but if you use the remote debugging connections for other purposes then you will probably need to ensure they are closed, because each connection uses a process as well as some other resources.
LispWorks User Guide and Reference Manual - 20 Sep 2017