Connection refused when using Rack Proxy - ruby

Question

I'm trying to catch all *.dev requests on port 80 and send them to the right Rack project by using Rack Proxy. I'm able to catch the requests and based on the URI I'll look for a config.ru in a specific folder. When I'm able to find one I'll boot up the server on port 3000.
After that, whenever I recieve a request on port 80, I try to set the HTTP_HOST to localhost:3000, but I'm getting the message Unexpected error while processing request: Connection refused - connect(2) for "localhost" port 3000. I am able to access the application through localhost:3000, but not through a *.dev domain. I already tried using different ports, but that's not working either, so I guess it has something to do with the user that's running it. However, I hope someone can help me with this.
require 'rack-proxy'
class AppProxy < Rack::Proxy
def rewrite_env(env)
request = Rack::Request.new(env)
site = request.host[0..-5]
uid = File.stat(__FILE__).uid
path = Etc.getpwuid(uid).dir + '/Software/Applications/'
front_controller = "#{path}#{site}/config.ru"
if File.file?(front_controller)
system "rackup -p 3000 -D #{front_controller} "
env["HTTP_HOST"] = "localhost:3000"
else
raise Exception.new "Not found"
end
env
end
end
run AppProxy.new
EDIT: I've checked if there is something listening on port 3000. After running the server and sudo lsof -i -n -P | grep TCP I get the following result for the ports 80 and 3000:
ruby 56247 root 10u IPv4 0x727d74bd0b95bd9b 0t0 TCP *:80 (LISTEN)
ruby 56247 root 11u IPv4 0x727d74bd0a3b9bfb 0t0 TCP 127.0.0.1:80->127.0.0.1:52773 (ESTABLISHED)
ruby 56255 root 12u IPv6 0x727d74bd094e3c8b 0t0 TCP [::1]:3000 (LISTEN)
I'm not sure if this is any useful because I don't know the exact meaning of this.

Answer 1

Solved it. The problem was that booting up the server was a bit slower then setting the HTTP_HOST to a different location and port 3000 was not in use yet. Waiting for a second solved the problem. My code looks like this now:
require 'rack-proxy'
class AppProxy < Rack::Proxy
def rewrite_env(env)
request = Rack::Request.new(env)
site = request.host[0..-5]
uid = File.stat(__FILE__).uid
path = Etc.getpwuid(uid).dir + '/Software/Applications/'
front_controller = "#{path}#{site}/config.ru"
if File.file?(front_controller)
system "rackup -D -p 3000 #{front_controller} "
sleep(1)
env["HTTP_HOST"] = "localhost:3000"
else
raise Exception.new "Not found"
end
env
end
end
run AppProxy.new