use IO::Socket::INET;
use warnings;
use strict;

# auto-flush on socket
$| = 1;

# creating a listening socket
# => Wir sind der Server fuer den Anwender
my $socket_server = new IO::Socket::INET (
LocalHost => '0.0.0.0',
LocalPort => '9000',
Proto => 'tcp',
Listen => 5,
Reuse => 1
);
die "cannot create socket $!\n" unless $socket_server;
print "server waiting for client connection on port 9200\n";

# create a connecting socket
# => Wir sind der Client fuer das Endgeraet
my $socket_client = new IO::Socket::INET (
PeerHost => 'destination-srv',
PeerPort => '9000',
Proto => 'tcp',
);
die "cannot connect to the server $!\n" unless $socket_client;
print "client-part connected to the server (endpoint)\n";

while(1)
{
  print "\n\n\n";
  
  # waiting for a new client connection
  my $client_socket = $socket_server->accept();
  
  # get information about a newly connected client
  my $client_address = $client_socket->peerhost();
  my $client_port = $client_socket->peerport();
  print "connection from $client_address:$client_port\n";
  
  # read up to 1024 characters from the connected client
  my $data = "";
  $client_socket->recv($data, 1024);
  print "mitm server received data: $data\n";
  
  #####################
  ### MITM-PART ###
  #####################
  
  my $size = $socket_client->send($data);
  print "mitm client sent data of length ".$size." (".$data.")\n";
  
  # notify server that request has been sent
  shutdown($socket_client, 1);
  
  # receive a response of up to 1024 characters from server
  my $response = "";
  $socket_client->recv($response, 1024);
  print "mitm client received response: $response\n";
  
  #####################
  ### MITM-PART ###
  #####################
  
  # write response data to the connected client
  print "mitm server is sending data to real client\n";
  $client_socket->send($response);
  print "mitm server has send data to real client\n";
  
  # notify client that response has been sent
  shutdown($client_socket, 1);
}

$socket_client->close();
$socket_server->close();