Das Telnet-Protokoll hat ein wenig von Verhandlungen an seinem Start manchmal etwas scherzhaft bezeichnet als "geheimer Händedruck". Sie sollten einen geradlinigeren Dienst/Port verwenden, um mit Sockets auf dem neuesten Stand zu sein.
Auch brauchen Sie wirklich zwei verschiedene Threads der Kontrolle für diese Art von Sache; Sonst ist es zu schwer. Hier ist ein einfaches telnetish Programm von 1998:
use strict;
use IO::Socket;
my ($host, $port, $kidpid, $handle, $line);
unless (@ARGV == 2) { die "usage: $0 host port" }
($host, $port) = @ARGV;
# create a tcp connection to the specified host and port
$handle = IO::Socket::INET->new(Proto => "tcp",
PeerAddr => $host,
PeerPort => $port)
or die "can't connect to port $port on $host: $!";
$handle->autoflush(1); # so output gets there right away
print STDERR "[Connected to $host:$port]\n";
# split the program into two processes, identical twins
die "can't fork: $!" unless defined($kidpid = fork());
if ($kidpid) {
# parent copies the socket to standard output
while (defined ($line = <$handle>)) {
print STDOUT $line;
}
kill("TERM" => $kidpid); # send SIGTERM to child
}
else {
# child copies standard input to the socket
while (defined ($line = <STDIN>)) {
print $handle $line;
}
}
exit;
Und hier ist eine vollständigere Umsetzung, ein Programm, das auf Ihren Firewall sitzt und wartet auf interne Verbindungen zu einem gewissen Außenhafen:
#!/usr/bin/perl -w
# fwdport -- act as proxy forwarder for dedicated services
use strict; # require declarations
use Getopt::Long; # for option processing
use Net::hostent; # by-name interface for host info
use IO::Socket; # for creating server and client sockets
use POSIX ":sys_wait_h"; # for reaping our dead children
my (
%Children, # hash of outstanding child processes
$REMOTE, # whom we connect to on the outside
$LOCAL, # where we listen to on the inside
$SERVICE, # our service name or port number
$proxy_server, # the socket we accept() from
$ME, # basename of this program
);
($ME = $0) =~ s,.*/,,; # retain just basename of script name
check_args(); # processing switches
start_proxy(); # launch our own server
service_clients(); # wait for incoming
die "NOT REACHED"; # you can't get here from there
# process command line switches using the extended
# version of the getopts library.
sub check_args {
GetOptions(
"remote=s" => \$REMOTE,
"local=s" => \$LOCAL,
"service=s" => \$SERVICE,
) or die <<EOUSAGE;
usage: $0 [ --remote host ] [ --local interface ] [ --service service ]
EOUSAGE
die "Need remote" unless $REMOTE;
die "Need local or service" unless $LOCAL || $SERVICE;
}
# begin our server
sub start_proxy {
my @proxy_server_config = (
Proto => 'tcp',
Reuse => 1,
Listen => SOMAXCONN,
);
push @proxy_server_config, LocalPort => $SERVICE if $SERVICE;
push @proxy_server_config, LocalAddr => $LOCAL if $LOCAL;
$proxy_server = IO::Socket::INET->new(@proxy_server_config)
or die "can't create proxy server: [email protected]";
print "[Proxy server on ", ($LOCAL || $SERVICE), " initialized.]\n";
}
sub service_clients {
my (
$local_client, # someone internal wanting out
$lc_info, # local client's name/port information
$remote_server, # the socket for escaping out
@rs_config, # temp array for remote socket options
$rs_info, # remote server's name/port information
$kidpid, # spawned child for each connection
);
$SIG{CHLD} = \&REAPER; # harvest the moribund
accepting();
# an accepted connection here means someone inside wants out
while ($local_client = $proxy_server->accept()) {
$lc_info = peerinfo($local_client);
set_state("servicing local $lc_info");
printf "[Connect from $lc_info]\n";
@rs_config = (
Proto => 'tcp',
PeerAddr => $REMOTE,
);
push(@rs_config, PeerPort => $SERVICE) if $SERVICE;
print "[Connecting to $REMOTE...";
set_state("connecting to $REMOTE"); # see below
$remote_server = IO::Socket::INET->new(@rs_config)
or die "remote server: [email protected]";
print "done]\n";
$rs_info = peerinfo($remote_server);
set_state("connected to $rs_info");
$kidpid = fork();
die "Cannot fork" unless defined $kidpid;
if ($kidpid) {
$Children{$kidpid} = time(); # remember his start time
close $remote_server; # no use to master
close $local_client; # likewise
next; # go get another client
}
# at this point, we are the forked child process dedicated
# to the incoming client. but we want a twin to make i/o
# easier.
close $proxy_server; # no use to slave
$kidpid = fork();
die "Cannot fork" unless defined $kidpid;
# now each twin sits around and ferries lines of data.
# see how simple the algorithm is when you can have
# multiple threads of control?
# this is the fork's parent, the master's child
if ($kidpid) {
set_state("$rs_info --> $lc_info");
select($local_client); $| = 1;
print while <$remote_server>;
kill('TERM', $kidpid); # kill my twin cause we're done
}
# this is the fork's child, the master's grandchild
else {
set_state("$rs_info <-- $lc_info");
select($remote_server); $| = 1;
print while <$local_client>;
kill('TERM', getppid()); # kill my twin cause we're done
}
exit; # whoever's still alive bites it
} continue {
accepting();
}
}
# helper function to produce a nice string in the form HOST:PORT
sub peerinfo {
my $sock = shift;
my $hostinfo = gethostbyaddr($sock->peeraddr);
return sprintf("%s:%s",
$hostinfo->name || $sock->peerhost,
$sock->peerport);
}
# reset our $0, which on some systems make "ps" report
# something interesting: the string we set $0 to!
sub set_state { $0 = "$ME [@_]" }
# helper function to call set_state
sub accepting {
set_state("accepting proxy for " . ($REMOTE || $SERVICE));
}
# somebody just died. keep harvesting the dead until
# we run out of them. check how long they ran.
sub REAPER {
my $child;
my $start;
while (($child = waitpid(-1,WNOHANG)) > 0) {
if ($start = $Children{$child}) {
my $runtime = time() - $start;
printf "Child $child ran %dm%ss\n",
$runtime/60, $runtime % 60;
delete $Children{$child};
} else {
print "Bizarre kid $child exited $?\n";
}
}
# If I had to choose between System V and 4.2, I'd resign. --Peter Honeyman
$SIG{CHLD} = \&REAPER;
};
Wie gesagt, Das ist von 1998. In diesen Tagen würde ich use warnings und möglicherweise use autodie, aber Sie sollten immer noch in der Lage sein, ein gutes Stück davon zu lernen.
Danke! Das hat geholfen! – Manoj