Proxy between single uplink and multiple clients. Implements http://ru-root.livejournal.com/2617418.html -- Proxy transmits requests from all clients to uplink connection. All responses are sent to all clients.

tcp3.pl

#!/usr/bin/perl

use strict;
use warnings;

# apt-get install libio-async-loop-epoll-perl
use IO::Async::Loop::Epoll;
use IO::Async::Socket;

use constant {
	DEFAULT_UPLINK_PORT => 1234,
	DEFAULT_LISTEN_PORT => 1235,
};

my $uplink_host;
my $uplink_port;
my $listen_port;

my $uplink_stream;
my %client_streams;

my $loop = IO::Async::Loop::Epoll->new;

$loop->connect(
	    host => $uplink_host ||= '127.0.0.1',
	 service => $uplink_port ||= DEFAULT_UPLINK_PORT,
	socktype => 'stream',

	on_stream => sub {
		my $uplink_stream = shift;
		$uplink_stream->configure(
			on_read => sub {
				my ($self, $bufref, $eof) = @_;
				$_->write($bufref) foreach keys %client_streams;
				$$bufref = "";
				return 0;
			},
			on_close => sub {
				$loop->stop
			},
		);
		$loop->add($uplink_stream);
	},
	on_connect_error => sub { die "FATAL: Cannot connect to uplink.\n" },
	on_resolve_error => sub { die "FATAL: Cannot resolve - $_[0]\n" },
);

$loop->listen(
	service => $listen_port || DEFAULT_LISTEN_PORT,
	socktype => 'stream',
	on_listen_error  => sub { die "FATAL: Cannot listen.\n" },
	on_resolve_error => sub { die "FATAL: Cannot resolve - $_[0]\n" },
	on_stream => sub {
		my ($self_listener, $stream) = @_;
		$client_streams{$stream} = 1;
		$stream->configure(
			on_read => sub {
				my ($self, $bufref, $eof) = @_;
				$uplink_stream->write($bufref);
				$$bufref = "";
				return 0;
			},
			on_closed => sub {
				my $self = shift;
				delete $client_streams{$self};
			}
		);
		$loop->add($stream);
	},
);

$loop->loop_forever;

__END__