XCOM and XFIL is used together with SERVER="exec" parameter.
A special protocol name "exec" means executing some local command
rather than connecting to a server. With "exec", DeleGate will work
like simple inetd or wrapper.
What will be executed is specified with either XCOM or XFIL parameter.
Commands executed as XCOM will be given standard I/O
which are bound for a socket connected to the client.
Commands executed as XFIL will be given standard I/O
which are redirected to a pair of pipes bound for DeleGate,
which relays it to and from the client.
On WindowsNT and OS/2, commands executed as XCOM will be given a
environment variable "SOCKHANDLE_CLIENT"
which have the handle value of the inherited socket
connected to the client.