set listen [socket -server [namespace code FcopyTestAccept] -myaddr 127.0.0.1 0]
    set in [open $thisScript]	;# 126 K
    set out [socket 127.0.0.1 [lindex [fconfigure $listen -sockname] 2]]
    catch {unset fcopyTestDone}
    close $listen	;# This means the socket open never really succeeds
    fcopy $in $out -command [namespace code FcopyTestDone]
    variable fcopyTestDone
    if {![info exists fcopyTestDone]} {
	vwait [namespace which -variable fcopyTestDone]		;# The error occurs here in the b.g.
    }
    close $in
    close $out
    set fcopyTestDone	;# 1 for error condition
} 1
test io-53.6 {CopyData: error during fcopy} {stdio fcopy} {
    variable fcopyTestDone
    file delete $path(pipe)
    file delete $path(test1)
    catch {unset fcopyTestDone}
    set f1 [open $path(pipe) w]
    puts $f1 "exit 1"
    close $f1
    set in [open "|[list [interpreter] $path(pipe)]" r+]
    set out [open $path(test1) w]
    fcopy $in $out -command [namespace code FcopyTestDone]
    variable fcopyTestDone
    if {![info exists fcopyTestDone]} {
	vwait [namespace which -variable fcopyTestDone]
    }
    catch {close $in}
    close $out
    set fcopyTestDone	;# 0 for plain end of file
} {0}
proc doFcopy {in out {bytes 0} {error {}}} {

	exit 0
    }
    close $f1
    set in [open "|[list [interpreter] $path(pipe) &]" r+]
    set out [open $path(test1) w]
    doFcopy $in $out
    variable fcopyTestDone
    if {![info exists fcopyTestDone]} {
	vwait [namespace which -variable fcopyTestDone]
    }
    catch {close $in}
    close $out
    # -1=error 0=script error N=number of bytes
    expr ($fcopyTestDone == 0) ? $fcopyTestCount : -1
} {3450}