simple-response.rb

#! /usr/bin/env ruby

require 'socket'

def log(source, message)
  time = Time.now.strftime("%Y-%m-%d %H:%M:%S")
  puts "[%s] %s => %s" % [time, source, message]
end

# Class representing HTTP Requests
Request = Struct.new(:method, :uri, :version, :headers) do
  def self.parse(client)
    # parse the request line
    method, uri, version = client.readline.split

    Request.new(method, uri, version, {}).tap do |r|
      # read the headers
      until (header_line = client.readline).strip == '' do
        header, value = header_line.split(':').map { |s| s.strip }
        r.headers[header] = value
      end
    end
  end
end

Response = Struct.new(:version, :status_code, :reason_phrase, :headers, :body) do
  def to_s
    response = "#{version} #{status_code} #{reason_phrase}\r\n"
    headers.each do |key, value|
      response << "#{key}: #{value}\r\n"
    end
    response << "\r\n"
    response << body
  end
end

server = TCPServer.new ARGV.first.to_i

loop do
  client = server.accept
  info = client.remote_address
  source = "%s:%s" % [info.ip_address, info.ip_port]

  log source, "Connection established"

  request = Request.parse(client)
  log source, "Method = %s | URI = %s | Version = %s" % [request.method, request.uri, request.version]
  log source, "Headers = %s" % request.headers.inspect

  response = Response.new("HTTP/1.1", 200, 'OK').tap do |r|
    r.body    = '<h1>Hello, world!</h1>'
    r.headers = {
      'Connection'     => 'close',
      'Content-Type'   => 'text/html',
      'Content-Length' => r.body.bytes.length
    }
  end
  client.write(response)
end