title: Change default port number of unicorn using config/unicorn/unicorn.rb configs
body: <p>How can i change unicorn's default port number using config/unicorn/unicorn.rb file configuration parameters. I need to run two unicorns with nginx on same machine how can i achieve this? Right now i am getting port address already occupied error.       </p>
  
  <pre><code>app_dir = "/home/rails/apps/app_name/current"
  shared_dir = "/home/rails/apps/app_name/shared"
  
  env = "staging"
  
  # Set unicorn options
  worker_processes 1
  preload_app true
  timeout 30
  
  # Fill path to your app
  working_directory app_dir
  
  # Set up socket location
  listen "#{shared_dir}/sockets/unicorn.admin.sock", :backlog =&gt; 64
  
  # Loging
  stderr_path "#{shared_dir}/log/unicorn.stderr.log"
  stdout_path "#{shared_dir}/log/unicorn.stdout.log"
  
  # Set master PID location
  pid "#{shared_dir}/pids/unicorn.admin.pid"
  
  before_fork do |server, worker|
    # server.listen(addr, :tries =&gt; -1, :delay =&gt; 5, :tcp_nopush =&gt; true)
    defined?(ActiveRecord::Base) and ActiveRecord::Base.connection.disconnect!
    old_pid = "#{server.config[:pid]}.oldbin"
    if File.exists?(old_pid) &amp;&amp; server.pid != old_pid
      begin
        sig = (worker.nr + 1) &gt;= server.worker_processes ? :QUIT : :TTOU
        Process.kill(sig, File.read(old_pid).to_i)
      rescue Errno::ENOENT, Errno::ESRCH
        # someone else did our job for us
      end
    end
  end
  
  after_fork do |server, worker|
    defined?(ActiveRecord::Base) and ActiveRecord::Base.establish_connection
  end
  
  before_exec do |server|
    ENV['BUNDLE_GEMFILE'] = "#{app_dir}/Gemfile"
  end
  </code></pre>
  
  <p>I am getting this error:</p>
  
  <pre><code>/shared/sockets/unicorn.admin.sock (Errno::EADDRINUSE)
  </code></pre>