diff --git a/greentulip/socket.py b/greentulip/socket.py
index 78a7668..d364042 100644
--- a/greentulip/socket.py
+++ b/greentulip/socket.py
@@ -13,6 +13,7 @@ from socket import error, SOCK_STREAM
 from socket import socket as std_socket
 
 from . import yield_from
+from . import GreenUnixSelectorLoop
 
 
 class socket:
@@ -24,6 +25,8 @@ class socket:
             self._sock = std_socket(*args, **kwargs)
         self._sock.setblocking(False)
         self._loop = tulip.get_event_loop()
+        assert isinstance(self._loop, GreenUnixSelectorLoop), \
+            'GreenUnixSelectorLoop event loop is required'
 
     @classmethod
     def from_socket(cls, sock):
@@ -93,12 +96,11 @@ class socket:
         return self.__class__.from_socket(sock), addr
 
     @_copydoc
-    def makefile(self, *args, **kwargs):
-        if args:
-            if args[0] == 'rb':
-                return ReadFile(self._loop, self._sock)
-            elif args[0] == 'wb':
-                return WriteFile(self._loop, self._sock)
+    def makefile(self, mode, *args, **kwargs):
+        if mode == 'rb':
+            return ReadFile(self._loop, self._sock)
+        elif mode == 'wb':
+            return WriteFile(self._loop, self._sock)
         raise NotImplementedError
 
     bind = _proxy('bind')
@@ -135,6 +137,15 @@ class ReadFile:
             res = fut.result()
             self._buf.extend(res)
 
+            if size <= len(self._buf):
+                data = self._buf[:size]
+                del self._buf[:size]
+                return data
+            else:
+                data = self._buf[:]
+                del self._buf[:]
+                return data
+
     def close(self):
         pass
 
@@ -144,7 +155,6 @@ class WriteFile:
     def __init__(self, loop, sock):
         self._loop = loop
         self._sock = sock
-        self._buf = bytearray()
 
     def write(self, data):
         fut = self._loop.sock_sendall(self._sock, data)
diff --git a/tests/test_socket.py b/tests/test_socket.py
index 7c635a5..29761e7 100644
--- a/tests/test_socket.py
+++ b/tests/test_socket.py
@@ -2,12 +2,12 @@
 # Copyright (c) 2013 Yury Selivanov
 # License: Apache 2.0
 ##
-import greentulip
-import greentulip.socket as greensocket
-
 import tulip
 import unittest
 
+import greentulip
+import greentulip.socket as greensocket
+
 
 class SocketTests(unittest.TestCase):
 
@@ -20,6 +20,11 @@ class SocketTests(unittest.TestCase):
         self.loop.close()
         tulip.set_event_loop_policy(None)
 
+    def test_socket_wrong_event_loop(self):
+        loop = tulip.DefaultEventLoopPolicy().new_event_loop()
+        tulip.set_event_loop(loop)
+        self.assertRaises(AssertionError, greensocket.socket)
+
     def test_socket_docs(self):
         self.assertIn('accept connections', greensocket.socket.listen.__doc__)
         self.assertIn('Receive', greensocket.socket.recv.__doc__)
@@ -109,3 +114,74 @@ class SocketTests(unittest.TestCase):
             greentulip.task(client)(greensocket.socket))
         thread.join(1)
         self.assertEqual(check, 2)
+
+    def test_files_socket_echo(self):
+        import socket as std_socket
+        import threading
+        import time
+
+        check = 0
+        ev = threading.Event()
+
+        def server(sock_factory):
+            socket = sock_factory()
+            socket.bind(('127.0.0.1', 0))
+
+            assert socket.fileno() is not None
+
+            nonlocal addr
+            addr = socket.getsockname()
+            socket.listen(1)
+
+            ev.set()
+
+            sock, client_addrs = socket.accept()
+            assert isinstance(sock, sock_factory)
+
+            rfile = sock.makefile('rb')
+            data = rfile.read(1024)
+            while not data.endswith(b'\r'):
+                data += rfile.read(1024)
+
+            wfile = sock.makefile('wb')
+            wfile.write(data)
+
+            ev.wait()
+            ev.clear()
+
+            sock.close()
+            socket.close()
+
+        def client(sock_factory):
+            ev.wait()
+            ev.clear()
+            time.sleep(0.1)
+
+            assert addr
+            sock = sock_factory()
+            sock.connect(addr)
+
+            data = b'hello greenlets\r'
+            sock.sendall(data)
+
+            rep = b''
+            while not rep.endswith(b'\r'):
+                rep += sock.recv(1024)
+
+            self.assertEqual(data, rep)
+            ev.set()
+
+            nonlocal check
+            check += 1
+
+            sock.close()
+
+        addr = None
+        ev.clear()
+        thread = threading.Thread(target=client, args=(std_socket.socket,))
+        thread.setDaemon(True)
+        thread.start()
+        self.loop.run_until_complete(
+            greentulip.task(server)(greensocket.socket))
+        thread.join(1)
+        self.assertEqual(check, 1)