Add puma.socket key for direct socket access

lib/puma/const.rb

@@ -103,6 +103,7 @@ module Puma
     RACK_INPUT = "rack.input".freeze
     RACK_URL_SCHEME = "rack.url_scheme".freeze
     RACK_AFTER_REPLY = "rack.after_reply".freeze
+    PUMA_SOCKET = "puma.socket".freeze
 
     HTTP = "http".freeze
     HTTPS = "https".freeze

lib/puma/server.rb

@@ -398,6 +398,8 @@ module Puma
     def handle_request(env, client, body, cl)
       normalize_env env, client
 
+      env[PUMA_SOCKET] = client
+
       if cl
         body = read_body env, client, body, cl
         return false unless body

test/test_puma_server.rb

@@ -76,4 +76,25 @@ class TestPumaServer < Test::Unit::TestCase
 
     assert_equal "#{fifteen}#{fifteen}", data
   end
+
+  def test_puma_socket
+    body = "HTTP/1.1 750 Upgraded to Awesome\r\nDone: Yep!\r\n"
+    @server.app = proc do |env|
+      io = env['puma.socket']
+
+      io.write body
+
+      io.close
+
+      [-1, {}, []]
+    end
+
+    @server.add_tcp_listener @host, @port
+    @server.run
+
+    sock = TCPSocket.new @host, @port
+    sock << "PUT / HTTP/1.0\r\n\r\nHello"
+
+    assert_equal body, sock.read
+  end
 end