x11vnc/misc/inet6to4 - platform/external/libvncserver - Git at Google

 #!/usr/bin/perl
 #
 # inet6to4:  Act as an ipv6-to-ipv4 relay for tcp applications that
 #            do not support ipv6.
 #
 # Usage:     inet6to4    <ipv6-listen-port> <ipv4-host:port>
 #            inet6to4 -r <ipv4-listen-port> <ipv6-host:port>
 #
 # Examples:  inet6to4 5900 localhost:5900
 #            inet6to4 8080 web1:80
 #            inet6to4 -r 5900 fe80::217:f2ff:fee6:6f5a%eth0:5900
 #
 # The -r option reverses the direction of translation (e.g. for ipv4
 # clients that need to connect to ipv6 servers.)  Reversing is the default
 # if this script is named 'inet4to6' (e.g. by a symlink.)
 #
 # Use Ctrl-C to stop this program.  You can also supply '-c n' as the
 # first option to only handle that many connections.
 #
 # Also set the env. vars INET6TO4_LOOP=1 or INET6TO4_LOOP=BG
 # to have an outer loop restarting this program (BG means do that
 # in the background), and INET6TO4_LOGFILE for a log file.
 # Also set INET6TO4_VERBOSE to verbosity level and INET6TO4_WAITTIME
 # and INET6TO4_PIDFILE (see below.)
 #

 #-------------------------------------------------------------------------
 # Copyright (c) 2010 by Karl J. Runge <runge@karlrunge.com>
 #
 # inet6to4 is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation; either version 2 of the License, or (at
 # your option) any later version.
 #
 # inet6to4 is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with inet6to4; if not, write to the Free Software
 # Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA
 # or see <http://www.gnu.org/licenses/>.
 #-------------------------------------------------------------------------

 my $program = "inet6to4";

 # Set up logging:
 #
 if (exists $ENV{INET6TO4_LOGFILE}) {
 	close STDOUT;
 	if (!open(STDOUT, ">>$ENV{INET6TO4_LOGFILE}")) {
 	        die "$program: $ENV{INET6TO4_LOGFILE} $!\n";
 	}
 	close STDERR;
 	open(STDERR, ">&STDOUT");
 }
 select(STDERR); $| = 1;
 select(STDOUT); $| = 1;

 # interrupt handler:
 #
 my $looppid = '';
 my $pidfile = '';
 my $listen_sock = '';	# declared here for get_out()
 #
 sub get_out {
 	print STDERR "$_[0]:\t$$ looppid=$looppid\n";
 	close $listen_sock if $listen_sock;
 	if ($looppid) {
 		kill 'TERM', $looppid;
 		fsleep(0.2);
 	}
 	unlink $pidfile if $pidfile;
 	exit 0;
 }
 $SIG{INT}  = \&get_out;
 $SIG{TERM} = \&get_out;

 # pidfile:
 #
 sub open_pidfile {
 	if (exists $ENV{INET6TO4_PIDFILE}) {
 		my $pf = $ENV{INET6TO4_PIDFILE};
 		if (open(PID, ">$pf")) {
 			print PID "$$\n";
 			close PID;
 			$pidfile = $pf;
 		} else {
 			print STDERR "could not open pidfile: $pf - $! - continuing...\n";
 		}
 		delete $ENV{INET6TO4_PIDFILE};
 	}
 }

 ####################################################################
 # Set INET6TO4_LOOP=1 to have this script create an outer loop
 # restarting itself if it ever exits.  Set INET6TO4_LOOP=BG to
 # do this in the background as a daemon.

 if (exists $ENV{INET6TO4_LOOP}) {
 	my $csl = $ENV{INET6TO4_LOOP};
 	if ($csl ne 'BG' && $csl ne '1') {
 		die "$program: invalid INET6TO4_LOOP.\n";
 	}
 	if ($csl eq 'BG') {
 		# go into bg as "daemon":
 		setpgrp(0, 0);
 		my $pid = fork();
 		if (! defined $pid) {
 			die "$program: $!\n";
 		} elsif ($pid) {
 			wait;
 			exit 0;
 		}
 		if (fork) {
 			exit 0;
 		}
 		setpgrp(0, 0);
 		close STDIN;
 		if (! $ENV{INET6TO4_LOGFILE}) {
 			close STDOUT;
 			close STDERR;
 		}
 	}
 	delete $ENV{INET6TO4_LOOP};

 	if (exists $ENV{INET6TO4_PIDFILE}) {
 		open_pidfile();
 	}

 	print STDERR "$program: starting service at ", scalar(localtime), " master-pid=$$\n";
 	while (1) {
 		$looppid = fork;
 		if (! defined $looppid) {
 			sleep 10;
 		} elsif ($looppid) {
 			wait;
 		} else {
 			exec $0, @ARGV;
 			exit 1;
 		}
 		print STDERR "$program: re-starting service at ", scalar(localtime), " master-pid=$$\n";
 		sleep 1;
 	}
 	exit 0;
 }
 if (exists $ENV{INET6TO4_PIDFILE}) {
 	open_pidfile();
 }

 use IO::Socket::INET6;
 use strict;
 use warnings;

 # some settings:
 #
 my $verbose = 1;	# set to 0 for no messages, 2 for more.
 my $killpid = 1;	# does kill(2) at end of connection.
 my $waittime = 0.25;	# time to wait between connections.
 my $reverse = 0;	# -r switch (or file named inet4to6)

 if (exists $ENV{INET6TO4_VERBOSE}) {
 	$verbose = $ENV{INET6TO4_VERBOSE};
 }
 if (exists $ENV{INET6TO4_WAITTIME}) {
 	$waittime = $ENV{INET6TO4_WAITTIME};
 }

 # process command line args:

 if (! @ARGV || $ARGV[0] =~ '^-+h') {	# -help
 	open(ME, "<$0");
 	while (<ME>) {
 		last unless /^#/;
 		next if /usr.bin.perl/;
 		$_ =~ s/# ?//;
 		print;
 	}
 	exit;
 }

 my $cmax = 0;
 if ($ARGV[0] eq '-c') {			# -c
 	shift;
 	$cmax = shift;
 }

 if ($ARGV[0] eq '-r') {			# -r
 	shift;
 	$reverse = 1;
 } elsif ($0 =~ /inet4to6$/) {
 	$reverse = 1;
 }

 my $listen_port = shift;		# ipv6-listen-port
 my $connect_to  = shift;		# ipv4-host:port

 die "no listen port or connect-to-host:port\n" if ! $listen_port || ! $connect_to;

 # connect to host:
 #
 my $host = '';
 my $port = '';
 if ($connect_to =~ /^(.*):(\d+)$/) {
 	$host = $1;
 	$port = $2;
 }
 die "invalid connect-to-host:port\n" if ! $host || ! $port;

 setpgrp(0, 0);

 # create listening socket:
 #
 my %opts;
 $opts{Listen}    = 10;
 $opts{Proto}     = "tcp";
 $opts{ReuseAddr} = 1;
 if ($listen_port =~ /^(.*):(\d+)$/) {
 	$opts{LocalAddr} = $1;
 	$listen_port = $2;
 }
 $opts{LocalPort} = $listen_port;

 if (!$reverse) {
 	# force ipv6 interface:
 	$opts{Domain} = AF_INET6;
 	$listen_sock = IO::Socket::INET6->new(%opts);
 } else {
 	$listen_sock = IO::Socket::INET->new(%opts);
 	if (! $listen_sock && $! =~ /invalid/i) {
 		warn "$program: $!, retrying with AF_UNSPEC:\n";
 		$opts{Domain} = AF_UNSPEC;
 		$listen_sock = IO::Socket::INET6->new(%opts);
 	}
 }
 if (! $listen_sock) {
 	die "$program: $!\n";
 }

 # for use by the xfer helper processes' interrupt handlers:
 #
 my $current_fh1 = '';
 my $current_fh2 = '';

 # connection counter:
 #
 my $conn = 0;

 # loop forever waiting for connections:
 #
 while (1) {
 	$conn++;
 	if ($cmax > 0 && $conn > $cmax) {
 		print STDERR "last connection ($cmax)\n" if $verbose;
 		last;
 	}
 	print STDERR "listening for connection: $conn\n" if $verbose;
 	my ($client, $ip) = $listen_sock->accept();

 	if ($client && !$reverse && $port == $listen_port) {
 		# This happens on Darwin 'tcp46'
 		if ($client->peerhost() =~ /^::ffff:/) {
 			print STDERR "closing client we think is actually us: ",
 			    $client->peerhost(), "\n";
 			close $client;
 			$client = undef;
 		}
 	}
 	if (! $client) {
 		# to throttle runaways
 		fsleep(2 * $waittime);
 		next;
 	}
 	print STDERR "conn: $conn -- ", $client->peerhost(), " at ", scalar(localtime), "\n" if $verbose;

 	# spawn helper:
 	#
 	my $pid = fork();
 	if (! defined $pid) {
 		die "$program: $!\n";
 	} elsif ($pid) {
 		wait;
 		# to throttle runaways
 		fsleep($waittime);
 		next;
 	} else {
 		# this is to avoid zombies:
 		close $listen_sock;
 		if (fork) {
 			exit 0;
 		}
 		setpgrp(0, 0);
 		handle_conn($client);
 	}
 }

 exit 0;

 sub handle_conn {
 	my $client = shift;

 	my $start = time();

 	print STDERR "connecting to: $host:$port\n" if $verbose;

 	my $sock = '';
 	my %opts;
 	$opts{PeerAddr} = $host;
 	$opts{PeerPort} = $port;
 	$opts{Proto}    = "tcp";
 	if (!$reverse) {
 		$sock = IO::Socket::INET->new(%opts);
 	} else {
 		$opts{Domain} = AF_INET6;
 		$sock = IO::Socket::INET6->new(%opts);
 	}
 	if (! $sock) {
 		warn "$program: $!, retrying with AF_UNSPEC:\n";
 		$opts{Domain} = AF_UNSPEC;
 		$sock = IO::Socket::INET6->new(%opts);
 	}

 	if (! $sock) {
 		close $client;
 		die "$program: $!\n";
 	}

 	$current_fh1 = $client;
 	$current_fh2 = $sock;

 	# interrupt handler:
 	#
 	$SIG{TERM} = sub {print STDERR "got sigterm\[$$]\n" if $verbose; close $current_fh1; close $current_fh2; exit 0};

 	# spawn another helper and transfer the data:
 	#
 	my $parent = $$;
 	if (my $child = fork()) {
 		xfer($sock, $client, 'S->C');
 		if ($killpid) {
 			fsleep(0.5);
 			kill 'TERM', $child;
 		}
 	} else {
 		xfer($client, $sock, 'C->S');
 		if ($killpid) {
 			fsleep(0.75);
 			kill 'TERM', $parent;
 		}
 	}

 	# done.
 	#
 	if ($verbose > 1) {
 		my $dt = time() - $start;
 		print STDERR "dt\[$$]: $dt\n";
 	}
 	exit 0;
 }

 # transfers data in one direction:
 #
 sub xfer {
 	my($in, $out, $lab) = @_;
 	my ($RIN, $WIN, $EIN, $ROUT);
 	$RIN = $WIN = $EIN = "";
 	$ROUT = "";
 	vec($RIN, fileno($in), 1) = 1;
 	vec($WIN, fileno($in), 1) = 1;
 	$EIN = $RIN | $WIN;
 	my $buf;

 	while (1) {
 		my $nf = 0;
 		while (! $nf) {
 			$nf = select($ROUT=$RIN, undef, undef, undef);
 		}
 		my $len = sysread($in, $buf, 8192);
 		if (! defined($len)) {
 			next if $! =~ /^Interrupted/;
 			print STDERR "$program\[$lab/$conn/$$]: $!\n";
 			last;
 		} elsif ($len == 0) {
 			print STDERR "$program\[$lab/$conn/$$]: "
 			    . "Input is EOF.\n";
 			last;
 		}

 		if ($verbose > 4) {
 			# verbose debugging of data:
 			syswrite(STDERR , "\n$lab: ", 6);
 			syswrite(STDERR , $buf, $len);
 		}

 		my $offset = 0;
 		my $quit = 0;
 		while ($len) {
 			my $written = syswrite($out, $buf, $len, $offset);
 			if (! defined $written) {
 				print STDERR "$program\[$lab/$conn/$$]: "
 				    . "Output is EOF. $!\n";
 				$quit = 1;
 				last;
 			}
 			$len -= $written;
 			$offset += $written;
 		}
 		last if $quit;
 	}
 	close($in);
 	close($out);
 }

 # sleep a fraction of a second:
 #
 sub fsleep {
 	my ($time) = @_;
 	select(undef, undef, undef, $time) if $time;
 }
	#!/usr/bin/perl
	#
	# inet6to4: Act as an ipv6-to-ipv4 relay for tcp applications that
	# do not support ipv6.
	#
	# Usage: inet6to4 <ipv6-listen-port> <ipv4-host:port>
	# inet6to4 -r <ipv4-listen-port> <ipv6-host:port>
	#
	# Examples: inet6to4 5900 localhost:5900
	# inet6to4 8080 web1:80
	# inet6to4 -r 5900 fe80::217:f2ff:fee6:6f5a%eth0:5900
	#
	# The -r option reverses the direction of translation (e.g. for ipv4
	# clients that need to connect to ipv6 servers.) Reversing is the default
	# if this script is named 'inet4to6' (e.g. by a symlink.)
	#
	# Use Ctrl-C to stop this program. You can also supply '-c n' as the
	# first option to only handle that many connections.
	#
	# Also set the env. vars INET6TO4_LOOP=1 or INET6TO4_LOOP=BG
	# to have an outer loop restarting this program (BG means do that
	# in the background), and INET6TO4_LOGFILE for a log file.
	# Also set INET6TO4_VERBOSE to verbosity level and INET6TO4_WAITTIME
	# and INET6TO4_PIDFILE (see below.)
	#

	#-------------------------------------------------------------------------
	# Copyright (c) 2010 by Karl J. Runge <runge@karlrunge.com>
	#
	# inet6to4 is free software; you can redistribute it and/or modify
	# it under the terms of the GNU General Public License as published by
	# the Free Software Foundation; either version 2 of the License, or (at
	# your option) any later version.
	#
	# inet6to4 is distributed in the hope that it will be useful,
	# but WITHOUT ANY WARRANTY; without even the implied warranty of
	# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	# GNU General Public License for more details.
	#
	# You should have received a copy of the GNU General Public License
	# along with inet6to4; if not, write to the Free Software
	# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA
	# or see <http://www.gnu.org/licenses/>.
	#-------------------------------------------------------------------------

	my $program = "inet6to4";

	# Set up logging:
	#
	if (exists $ENV{INET6TO4_LOGFILE}) {
	close STDOUT;
	if (!open(STDOUT, ">>$ENV{INET6TO4_LOGFILE}")) {
	die "$program: $ENV{INET6TO4_LOGFILE} $!\n";
	}
	close STDERR;
	open(STDERR, ">&STDOUT");
	}
	select(STDERR); $\| = 1;
	select(STDOUT); $\| = 1;

	# interrupt handler:
	#
	my $looppid = '';
	my $pidfile = '';
	my $listen_sock = ''; # declared here for get_out()
	#
	sub get_out {
	print STDERR "$_[0]:\t$$ looppid=$looppid\n";
	close $listen_sock if $listen_sock;
	if ($looppid) {
	kill 'TERM', $looppid;
	fsleep(0.2);
	}
	unlink $pidfile if $pidfile;
	exit 0;
	}
	$SIG{INT} = \&get_out;
	$SIG{TERM} = \&get_out;

	# pidfile:
	#
	sub open_pidfile {
	if (exists $ENV{INET6TO4_PIDFILE}) {
	my $pf = $ENV{INET6TO4_PIDFILE};
	if (open(PID, ">$pf")) {
	print PID "$$\n";
	close PID;
	$pidfile = $pf;
	} else {
	print STDERR "could not open pidfile: $pf - $! - continuing...\n";
	}
	delete $ENV{INET6TO4_PIDFILE};
	}
	}

	####################################################################
	# Set INET6TO4_LOOP=1 to have this script create an outer loop
	# restarting itself if it ever exits. Set INET6TO4_LOOP=BG to
	# do this in the background as a daemon.

	if (exists $ENV{INET6TO4_LOOP}) {
	my $csl = $ENV{INET6TO4_LOOP};
	if ($csl ne 'BG' && $csl ne '1') {
	die "$program: invalid INET6TO4_LOOP.\n";
	}
	if ($csl eq 'BG') {
	# go into bg as "daemon":
	setpgrp(0, 0);
	my $pid = fork();
	if (! defined $pid) {
	die "$program: $!\n";
	} elsif ($pid) {
	wait;
	exit 0;
	}
	if (fork) {
	exit 0;
	}
	setpgrp(0, 0);
	close STDIN;
	if (! $ENV{INET6TO4_LOGFILE}) {
	close STDOUT;
	close STDERR;
	}
	}
	delete $ENV{INET6TO4_LOOP};

	if (exists $ENV{INET6TO4_PIDFILE}) {
	open_pidfile();
	}

	print STDERR "$program: starting service at ", scalar(localtime), " master-pid=$$\n";
	while (1) {
	$looppid = fork;
	if (! defined $looppid) {
	sleep 10;
	} elsif ($looppid) {
	wait;
	} else {
	exec $0, @ARGV;
	exit 1;
	}
	print STDERR "$program: re-starting service at ", scalar(localtime), " master-pid=$$\n";
	sleep 1;
	}
	exit 0;
	}
	if (exists $ENV{INET6TO4_PIDFILE}) {
	open_pidfile();
	}

	use IO::Socket::INET6;
	use strict;
	use warnings;

	# some settings:
	#
	my $verbose = 1; # set to 0 for no messages, 2 for more.
	my $killpid = 1; # does kill(2) at end of connection.
	my $waittime = 0.25; # time to wait between connections.
	my $reverse = 0; # -r switch (or file named inet4to6)

	if (exists $ENV{INET6TO4_VERBOSE}) {
	$verbose = $ENV{INET6TO4_VERBOSE};
	}
	if (exists $ENV{INET6TO4_WAITTIME}) {
	$waittime = $ENV{INET6TO4_WAITTIME};
	}

	# process command line args:

	if (! @ARGV \|\| $ARGV[0] =~ '^-+h') { # -help
	open(ME, "<$0");
	while (<ME>) {
	last unless /^#/;
	next if /usr.bin.perl/;
	$_ =~ s/# ?//;
	print;
	}
	exit;
	}

	my $cmax = 0;
	if ($ARGV[0] eq '-c') { # -c
	shift;
	$cmax = shift;
	}

	if ($ARGV[0] eq '-r') { # -r
	shift;
	$reverse = 1;
	} elsif ($0 =~ /inet4to6$/) {
	$reverse = 1;
	}

	my $listen_port = shift; # ipv6-listen-port
	my $connect_to = shift; # ipv4-host:port

	die "no listen port or connect-to-host:port\n" if ! $listen_port \|\| ! $connect_to;

	# connect to host:
	#
	my $host = '';
	my $port = '';
	if ($connect_to =~ /^(.*):(\d+)$/) {
	$host = $1;
	$port = $2;
	}
	die "invalid connect-to-host:port\n" if ! $host \|\| ! $port;

	setpgrp(0, 0);

	# create listening socket:
	#
	my %opts;
	$opts{Listen} = 10;
	$opts{Proto} = "tcp";
	$opts{ReuseAddr} = 1;
	if ($listen_port =~ /^(.*):(\d+)$/) {
	$opts{LocalAddr} = $1;
	$listen_port = $2;
	}
	$opts{LocalPort} = $listen_port;

	if (!$reverse) {
	# force ipv6 interface:
	$opts{Domain} = AF_INET6;
	$listen_sock = IO::Socket::INET6->new(%opts);
	} else {
	$listen_sock = IO::Socket::INET->new(%opts);
	if (! $listen_sock && $! =~ /invalid/i) {
	warn "$program: $!, retrying with AF_UNSPEC:\n";
	$opts{Domain} = AF_UNSPEC;
	$listen_sock = IO::Socket::INET6->new(%opts);
	}
	}
	if (! $listen_sock) {
	die "$program: $!\n";
	}

	# for use by the xfer helper processes' interrupt handlers:
	#
	my $current_fh1 = '';
	my $current_fh2 = '';

	# connection counter:
	#
	my $conn = 0;

	# loop forever waiting for connections:
	#
	while (1) {
	$conn++;
	if ($cmax > 0 && $conn > $cmax) {
	print STDERR "last connection ($cmax)\n" if $verbose;
	last;
	}
	print STDERR "listening for connection: $conn\n" if $verbose;
	my ($client, $ip) = $listen_sock->accept();

	if ($client && !$reverse && $port == $listen_port) {
	# This happens on Darwin 'tcp46'
	if ($client->peerhost() =~ /^::ffff:/) {
	print STDERR "closing client we think is actually us: ",
	$client->peerhost(), "\n";
	close $client;
	$client = undef;
	}
	}
	if (! $client) {
	# to throttle runaways
	fsleep(2 * $waittime);
	next;
	}
	print STDERR "conn: $conn -- ", $client->peerhost(), " at ", scalar(localtime), "\n" if $verbose;

	# spawn helper:
	#
	my $pid = fork();
	if (! defined $pid) {
	die "$program: $!\n";
	} elsif ($pid) {
	wait;
	# to throttle runaways
	fsleep($waittime);
	next;
	} else {
	# this is to avoid zombies:
	close $listen_sock;
	if (fork) {
	exit 0;
	}
	setpgrp(0, 0);
	handle_conn($client);
	}
	}

	exit 0;

	sub handle_conn {
	my $client = shift;

	my $start = time();

	print STDERR "connecting to: $host:$port\n" if $verbose;

	my $sock = '';
	my %opts;
	$opts{PeerAddr} = $host;
	$opts{PeerPort} = $port;
	$opts{Proto} = "tcp";
	if (!$reverse) {
	$sock = IO::Socket::INET->new(%opts);
	} else {
	$opts{Domain} = AF_INET6;
	$sock = IO::Socket::INET6->new(%opts);
	}
	if (! $sock) {
	warn "$program: $!, retrying with AF_UNSPEC:\n";
	$opts{Domain} = AF_UNSPEC;
	$sock = IO::Socket::INET6->new(%opts);
	}

	if (! $sock) {
	close $client;
	die "$program: $!\n";
	}

	$current_fh1 = $client;
	$current_fh2 = $sock;

	# interrupt handler:
	#
	$SIG{TERM} = sub {print STDERR "got sigterm\[$$]\n" if $verbose; close $current_fh1; close $current_fh2; exit 0};

	# spawn another helper and transfer the data:
	#
	my $parent = $$;
	if (my $child = fork()) {
	xfer($sock, $client, 'S->C');
	if ($killpid) {
	fsleep(0.5);
	kill 'TERM', $child;
	}
	} else {
	xfer($client, $sock, 'C->S');
	if ($killpid) {
	fsleep(0.75);
	kill 'TERM', $parent;
	}
	}

	# done.
	#
	if ($verbose > 1) {
	my $dt = time() - $start;
	print STDERR "dt\[$$]: $dt\n";
	}
	exit 0;
	}

	# transfers data in one direction:
	#
	sub xfer {
	my($in, $out, $lab) = @_;
	my ($RIN, $WIN, $EIN, $ROUT);
	$RIN = $WIN = $EIN = "";
	$ROUT = "";
	vec($RIN, fileno($in), 1) = 1;
	vec($WIN, fileno($in), 1) = 1;
	$EIN = $RIN \| $WIN;
	my $buf;

	while (1) {
	my $nf = 0;
	while (! $nf) {
	$nf = select($ROUT=$RIN, undef, undef, undef);
	}
	my $len = sysread($in, $buf, 8192);
	if (! defined($len)) {
	next if $! =~ /^Interrupted/;
	print STDERR "$program\[$lab/$conn/$$]: $!\n";
	last;
	} elsif ($len == 0) {
	print STDERR "$program\[$lab/$conn/$$]: "
	. "Input is EOF.\n";
	last;
	}

	if ($verbose > 4) {
	# verbose debugging of data:
	syswrite(STDERR , "\n$lab: ", 6);
	syswrite(STDERR , $buf, $len);
	}

	my $offset = 0;
	my $quit = 0;
	while ($len) {
	my $written = syswrite($out, $buf, $len, $offset);
	if (! defined $written) {
	print STDERR "$program\[$lab/$conn/$$]: "
	. "Output is EOF. $!\n";
	$quit = 1;
	last;
	}
	$len -= $written;
	$offset += $written;
	}
	last if $quit;
	}
	close($in);
	close($out);
	}

	# sleep a fraction of a second:
	#
	sub fsleep {
	my ($time) = @_;
	select(undef, undef, undef, $time) if $time;
	}