#!/usr/bin/perl
use Socket;
use FileHandle;

socket(SOCK, PF_INET, SOCK_STREAM, getprotobyname("tcp")) or die "socket: $!";
setsockopt(SOCK, SOL_SOCKET, SO_REUSEADDR, pack("l", 1))  or warn "setsockopt: $!";
bind(SOCK, sockaddr_in(8080, inet_aton("localhost"))) or die "bind: $!";
listen(SOCK, SOMAXCONN) or die "listen: $!";

while ( accept(my $sock = FileHandle->new(), SOCK) ) {

    printf STDERR "before aliasing: sock=%d, STDIN=%d, STDOUT=%d\n",
                  fileno($sock), fileno(STDIN), fileno(STDOUT);
    
    *STDIN  = $sock;
    *STDOUT = $sock;
    
    printf STDERR "after aliasing:  sock=%d, STDIN=%d, STDOUT=%d\n",
                  fileno($sock), fileno(STDIN), fileno(STDOUT);
    
    $| = 1;
    print "enter something:\n";
    my $r = <STDIN>;
    print "you typed: $r";

    close $sock;
}

##</code><code>##

$ perl ./aliasing1.pl
before aliasing: sock=5, STDIN=0, STDOUT=1
after aliasing:  sock=5, STDIN=5, STDOUT=5
^C
$

##</code><code>##

$ telnet localhost 8080
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
enter something:
foo
you typed: foo
Connection closed by foreign host.

##</code><code>##

$ perl -d ./aliasing1.pl

Loading DB routines from perl5db.pl version 1.28
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(./aliasing1.pl:5):    socket(SOCK, PF_INET, SOCK_STREAM, getprotobyname("tcp")) or die "socket: $!";
  DB<1> c
before aliasing: sock=9, STDIN=0, STDOUT=1
after aliasing:  sock=9, STDIN=0, STDOUT=1
enter something:
foo
you typed: foo
^C
IO::Handle::DESTROY(/usr/local/perl-5.8.8/lib/5.8.8/i686-linux/IO/Handle.pm:328):
328:    sub DESTROY {}
  DB<1> q
$

##</code><code>##

POSIX::dup2(fileno($sock), 0) or die "Cannot dup sock to STDIN: $!";
POSIX::dup2(fileno($sock), 1) or die "Cannot dup sock to STDOUT: $!";

##</code><code>##

open STDIN,  "<&", $sock or die "Cannot dup sock to STDIN: $!";
open STDOUT, ">&", $sock or die "Cannot dup sock to STDOUT: $!";

##</code><code>##

#!/usr/bin/perl

my $file = "foo.out";
open my $fh, ">", $file or die "cannot open $file: $!";

printf STDERR "fds before aliasing: fh=%d, STDOUT=%d\n",
              fileno($fh), fileno(STDOUT);

*STDOUT = $fh;

printf STDERR "fds after aliasing:  fh=%d, STDOUT=%d\n",
              fileno($fh), fileno(STDOUT);

print "foo\n";

##</code><code>##

$ perl ./aliasing2.pl
fds before aliasing: fh=3, STDOUT=1
fds after aliasing:  fh=3, STDOUT=3

##</code><code>##

$ perl -d ./aliasing2.pl

Loading DB routines from perl5db.pl version 1.28
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(./aliasing2.pl:3):    my $file = "foo.out";
  DB<1> c
fds before aliasing: fh=8, STDOUT=1
fds after aliasing:  fh=8, STDOUT=8
Debugged program terminated.  Use q to quit or R to restart,
  use o inhibit_exit to avoid stopping after program termination,
  h q, h R or h o to get additional info.  
  DB<1> q