How to Build a Super Simple HTTP Proxy in Perl in just 20 lines of code

Oct 1, 2023 ยท 3 min read

Perl is a great language for writing network applications thanks to its strong text processing capabilities and support for sockets. In this post we will build a basic HTTP proxy server in Perl in less than 20 lines of code.

First we load the required modules:

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

The IO::Socket::INET module will allow us to create TCP sockets and listen for connections. The LWP::UserAgent module makes it easy to fetch web pages.

Next we create a socket and bind it to port 8080 to listen for incoming connections:

my $socket = IO::Socket::INET->new(
  LocalHost => '127.0.0.1',
  LocalPort => '8080',
  Proto => 'tcp',
  Listen => 1,
  Reuse => 1
) or die "Cannot create socket: $!\\n";

We enable socket reuse and start listening for connections.

Then in an infinite loop we wait for a client to connect, read the HTTP request, extract the URL, fetch the web page, and return the response:

while (my $client = $socket->accept()) {

  my $request = <$client>;
  my $url = parse_url($request);

  my $ua = LWP::UserAgent->new;
  my $response = $ua->get($url);

  print $client $response->content;

  close $client;
}

The parse_url function extracts the URL from the HTTP request:

sub parse_url {
  my $request = shift;
  return (split / /, $request)[1];
}

We split the request string on spaces and return the URL portion.

The full proxy code is:

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

my $socket = IO::Socket::INET->new(
  LocalHost => '127.0.0.1',
  LocalPort => '8080',
  Proto => 'tcp',
  Listen => 1,
  Reuse => 1
) or die "Cannot create socket: $!\\n";

sub parse_url {
  my $request = shift;
  return (split / /, $request)[1];
}

while (my $client = $socket->accept()) {

  my $request = <$client>;
  my $url = parse_url($request);

  my $ua = LWP::UserAgent->new;
  my $response = $ua->get($url);

  print $client $response->content;

  close $client;
}

This demonstrates how to build a simple HTTP proxy server in Perl using less than 20 lines of code.

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