A trivial HTTP proxy server for testing and troubleshooting

http-proxy-server.rb

# This is a trivial HTTP proxy server, intended for use as a troubleshooting tool
# ONLY (not for real, actual, production use). I wrote this because I couldn't find
# a simple HTTP proxy that I could use to test HTTP proxy support in Net::SSH.
#
# This code is in the public domain, so do with it what you will!

require 'socket'

port = ARGV.shift || 8080
address = ARGV.shift || "127.0.0.1"

puts "starting proxy on #{address}:#{port}"
server = TCPServer.new(address, port)

loop do
  client = server.accept

  request = client.readline
  headers = {}
  loop do
    line = client.readline.strip
    break if line.empty?

    key, value = line.split(/:\s*/, 2)
    headers[key.downcase] = value
  end

  if request =~ /^CONNECT (.*?):(\d+) HTTP/
    host = $1
    port = $2.to_i

    puts "proxying to #{host}:#{port}"
    client.write "HTTP/1.0 200 OK\r\n\r\n"

    proxy = TCPSocket.new(host, port)
    loop do
      r, = IO.select([client, proxy])

      if r.include?(client)
        data = client.recv(1024)
        break if data.nil? || data.empty?
        proxy.write(data)
      end

      if r.include?(proxy)
        data = proxy.recv(1024)
        break if data.nil? || data.empty?
        client.write(data)
      end
    end
    proxy.close
  else
    puts "not a CONNECT request #{request.inspect}"
  end

  client.close
end