simple_server.rb

require 'webrick'

PORT = 7999

server = WEBrick::HTTPServer.new(
  Port: PORT,
  BindAddress: '0.0.0.0',
  Logger: WEBrick::Log.new('/dev/null')
)

server.mount_proc '/' do |req, res|
  res.body = 'Hello, forward!'
end

%w[INT TERM].each do |signal|
  trap(signal) { server.shutdown }
end

puts "\033[32mServer started on port #{PORT}, run `forward #{PORT}' in another terminal window to start a tunnel.\033[0m"

server.start