It's a webserver

server.rb

require 'socket'
server = TCPServer.new 5678

while session = server.accept
  request = session.gets
  puts request

  unless request.nil?

    filename = request.split(" ")[1]
    if filename == "/"
      filename = "/index.html"
    end

    begin
      data = File.open(__dir__ + filename).read

      session.print "HTTP/1.1 200 OK\r\n"
      session.print "Content-Type: text/html\r\n"
      session.print "\r\n"
      session.print data
    rescue
      session.print "HTTP/1.1 404 NOT FOUND\r\n"
      session.print "Content-Type: text/html\r\n"
      session.print "\r\n"
      session.print "You #FAIL"
    end

  end

  session.close
end