diff --git a/tornado/test/httpclient_test.py b/tornado/test/httpclient_test.py
index 08afff08..54ebc749 100644
--- a/tornado/test/httpclient_test.py
+++ b/tornado/test/httpclient_test.py
@@ -8,10 +8,9 @@ from contextlib import closing
 import functools
 
 from tornado.escape import utf8
-from tornado.httpclient import AsyncHTTPClient
 from tornado.iostream import IOStream
 from tornado import netutil
-from tornado.testing import AsyncHTTPTestCase, get_unused_port
+from tornado.testing import AsyncHTTPTestCase, bind_unused_port
 from tornado.util import b, bytes_type
 from tornado.web import Application, RequestHandler, url
 
@@ -108,8 +107,7 @@ class HTTPClientCommonTestCase(AsyncHTTPTestCase):
     def test_chunked_close(self):
         # test case in which chunks spread read-callback processing
         # over several ioloop iterations, but the connection is already closed.
-        port = get_unused_port()
-        (sock,) = netutil.bind_sockets(port, address="127.0.0.1")
+        sock, port = bind_unused_port()
         with closing(sock):
             def write_response(stream, request_data):
                 stream.write(b("""\
diff --git a/tornado/test/ioloop_test.py b/tornado/test/ioloop_test.py
index 63ef31f5..a679b07f 100644
--- a/tornado/test/ioloop_test.py
+++ b/tornado/test/ioloop_test.py
@@ -3,12 +3,10 @@
 
 from __future__ import absolute_import, division, with_statement
 import datetime
-import socket
 import time
 
 from tornado.ioloop import IOLoop
-from tornado.netutil import bind_sockets
-from tornado.testing import AsyncTestCase, get_unused_port
+from tornado.testing import AsyncTestCase, bind_unused_port
 from tornado.test.util import unittest
 
 
@@ -35,8 +33,7 @@ class TestIOLoop(AsyncTestCase):
         self.wait()
 
     def test_multiple_add(self):
-        [sock] = bind_sockets(get_unused_port(), '127.0.0.1',
-                              family=socket.AF_INET)
+        sock, port = bind_unused_port()
         try:
             self.io_loop.add_handler(sock.fileno(), lambda fd, events: None,
                                      IOLoop.READ)
diff --git a/tornado/test/iostream_test.py b/tornado/test/iostream_test.py
index 0a4c1258..d06c69b3 100644
--- a/tornado/test/iostream_test.py
+++ b/tornado/test/iostream_test.py
@@ -3,7 +3,7 @@ from tornado import netutil
 from tornado.ioloop import IOLoop
 from tornado.iostream import IOStream, SSLIOStream
 from tornado.log import gen_log
-from tornado.testing import AsyncHTTPTestCase, AsyncHTTPSTestCase, AsyncTestCase, get_unused_port, ExpectLog
+from tornado.testing import AsyncHTTPTestCase, AsyncHTTPSTestCase, AsyncTestCase, bind_unused_port, ExpectLog
 from tornado.test.util import unittest
 from tornado.util import b
 from tornado.web import RequestHandler, Application
@@ -120,9 +120,7 @@ class TestIOStreamMixin(object):
         raise NotImplementedError()
 
     def make_iostream_pair(self, **kwargs):
-        port = get_unused_port()
-        [listener] = netutil.bind_sockets(port, '127.0.0.1',
-                                          family=socket.AF_INET)
+        listener, port = bind_unused_port()
         streams = [None, None]
 
         def accept_callback(connection, address):
@@ -168,7 +166,8 @@ class TestIOStreamMixin(object):
         # When a connection is refused, the connect callback should not
         # be run.  (The kqueue IOLoop used to behave differently from the
         # epoll IOLoop in this respect)
-        port = get_unused_port()
+        server_socket, port = bind_unused_port()
+        server_socket.close()
         stream = IOStream(socket.socket(), self.io_loop)
         self.connect_called = False
 
diff --git a/tornado/test/process_test.py b/tornado/test/process_test.py
index 69ac6847..d076cac4 100644
--- a/tornado/test/process_test.py
+++ b/tornado/test/process_test.py
@@ -10,10 +10,9 @@ from tornado.httpclient import HTTPClient, HTTPError
 from tornado.httpserver import HTTPServer
 from tornado.ioloop import IOLoop
 from tornado.log import gen_log
-from tornado.netutil import bind_sockets
 from tornado.process import fork_processes, task_id
 from tornado.simple_httpclient import SimpleAsyncHTTPClient
-from tornado.testing import get_unused_port, ExpectLog
+from tornado.testing import bind_unused_port, ExpectLog
 from tornado.test.util import unittest
 from tornado.web import RequestHandler, Application
 
@@ -50,11 +49,10 @@ class ProcessTest(unittest.TestCase):
     def test_multi_process(self):
         with ExpectLog(gen_log, "(Starting .* processes|child .* exited|uncaught exception)"):
             self.assertFalse(IOLoop.initialized())
-            port = get_unused_port()
+            sock, port = bind_unused_port()
 
             def get_url(path):
                 return "http://127.0.0.1:%d%s" % (port, path)
-            sockets = bind_sockets(port, "127.0.0.1")
             # ensure that none of these processes live too long
             signal.alarm(5)  # master process
             try:
@@ -66,19 +64,17 @@ class ProcessTest(unittest.TestCase):
                 # finished with status 0
                 self.assertEqual(e.code, 0)
                 self.assertTrue(task_id() is None)
-                for sock in sockets:
-                    sock.close()
+                sock.close()
                 return
             try:
                 if id in (0, 1):
                     self.assertEqual(id, task_id())
                     server = HTTPServer(self.get_app())
-                    server.add_sockets(sockets)
+                    server.add_sockets([sock])
                     IOLoop.instance().start()
                 elif id == 2:
                     self.assertEqual(id, task_id())
-                    for sock in sockets:
-                        sock.close()
+                    sock.close()
                     # Always use SimpleAsyncHTTPClient here; the curl
                     # version appears to get confused sometimes if the
                     # connection gets closed before it's had a chance to
diff --git a/tornado/test/simple_httpclient_test.py b/tornado/test/simple_httpclient_test.py
index 05a35066..dbd836a3 100644
--- a/tornado/test/simple_httpclient_test.py
+++ b/tornado/test/simple_httpclient_test.py
@@ -17,7 +17,7 @@ from tornado.log import gen_log
 from tornado.simple_httpclient import SimpleAsyncHTTPClient, _DEFAULT_CA_CERTS
 from tornado.test.httpclient_test import ChunkHandler, CountdownHandler, HelloWorldHandler
 from tornado.test import httpclient_test
-from tornado.testing import AsyncHTTPTestCase, AsyncTestCase, get_unused_port, ExpectLog
+from tornado.testing import AsyncHTTPTestCase, AsyncTestCase, bind_unused_port, ExpectLog
 from tornado.test.util import unittest
 from tornado.util import b
 from tornado.web import RequestHandler, Application, asynchronous, url
@@ -288,7 +288,8 @@ class SimpleHTTPClientTestCase(AsyncHTTPTestCase):
         self.assertTrue(host_re.match(response.body), response.body)
 
     def test_connection_refused(self):
-        port = get_unused_port()
+        server_socket, port = bind_unused_port()
+        server_socket.close()
         with ExpectLog(gen_log, ".*"):
             self.http_client.fetch("http://localhost:%d/" % port, self.stop)
             response = self.wait()
diff --git a/tornado/test/twisted_test.py b/tornado/test/twisted_test.py
index 997dc129..7521d740 100644
--- a/tornado/test/twisted_test.py
+++ b/tornado/test/twisted_test.py
@@ -42,9 +42,10 @@ except ImportError:
     have_twisted = False
 
 from tornado.httpclient import AsyncHTTPClient
+from tornado.httpserver import HTTPServer
 from tornado.ioloop import IOLoop
 from tornado.platform.auto import set_close_exec
-from tornado.testing import get_unused_port
+from tornado.testing import bind_unused_port
 from tornado.test.util import unittest
 from tornado.util import import_object
 from tornado.web import RequestHandler, Application
@@ -344,8 +345,8 @@ class CompatibilityTests(unittest.TestCase):
             def render_GET(self, request):
                 return "Hello from twisted!"
         site = Site(HelloResource())
-        self.twisted_port = get_unused_port()
-        self.reactor.listenTCP(self.twisted_port, site, interface='127.0.0.1')
+        port = self.reactor.listenTCP(0, site, interface='127.0.0.1')
+        self.twisted_port = port.getHost().port
 
     def start_tornado_server(self):
         class HelloHandler(RequestHandler):
@@ -353,8 +354,9 @@ class CompatibilityTests(unittest.TestCase):
                 self.write("Hello from tornado!")
         app = Application([('/', HelloHandler)],
                           log_function=lambda x: None)
-        self.tornado_port = get_unused_port()
-        app.listen(self.tornado_port, address='127.0.0.1', io_loop=self.io_loop)
+        server = HTTPServer(app, io_loop=self.io_loop)
+        sock, self.tornado_port = bind_unused_port()
+        server.add_sockets([sock])
 
     def run_ioloop(self):
         self.stop_loop = self.io_loop.stop
diff --git a/tornado/testing.py b/tornado/testing.py
index be507d38..5b529a26 100644
--- a/tornado/testing.py
+++ b/tornado/testing.py
@@ -26,12 +26,14 @@ try:
     from tornado.httpserver import HTTPServer
     from tornado.simple_httpclient import SimpleAsyncHTTPClient
     from tornado.ioloop import IOLoop
+    from tornado import netutil
 except ImportError:
     # These modules are not importable on app engine.  Parts of this module
     # won't work, but e.g. LogTrapTestCase and main() will.
     AsyncHTTPClient = None
     HTTPServer = None
     IOLoop = None
+    netutil = None
     SimpleAsyncHTTPClient = None
 from tornado.log import gen_log
 from tornado.stack_context import StackContext, NullContext
@@ -41,6 +43,7 @@ import logging
 import os
 import re
 import signal
+import socket
 import sys
 import time
 
@@ -57,13 +60,31 @@ _next_port = 10000
 
 
 def get_unused_port():
-    """Returns a (hopefully) unused port number."""
+    """Returns a (hopefully) unused port number.
+
+    This function does not guarantee that the port it returns is available,
+    only that a series of get_unused_port calls in a single process return
+    distinct ports.
+
+    **Deprecated**.  Use bind_unused_port instead, which is guaranteed
+    to find an unused port.
+    """
     global _next_port
     port = _next_port
     _next_port = _next_port + 1
     return port
 
 
+def bind_unused_port():
+    """Binds a server socket to an available port on localhost.
+
+    Returns a tuple (socket, port).
+    """
+    [sock] = netutil.bind_sockets(0, 'localhost', family=socket.AF_INET)
+    port = sock.getsockname()[1]
+    return sock, port
+
+
 class AsyncTestCase(unittest.TestCase):
     """TestCase subclass for testing IOLoop-based asynchronous code.
 
@@ -248,7 +269,9 @@ class AsyncHTTPTestCase(AsyncTestCase):
         self.http_client = self.get_http_client()
         self._app = self.get_app()
         self.http_server = self.get_http_server()
-        self.http_server.listen(self.get_http_port(), address="127.0.0.1")
+        sock, port = bind_unused_port()
+        self.http_server.add_sockets([sock])
+        self.__port = port
 
     def get_http_client(self):
         return AsyncHTTPClient(io_loop=self.io_loop)
@@ -285,8 +308,6 @@ class AsyncHTTPTestCase(AsyncTestCase):
 
         A new port is chosen for each test.
         """
-        if self.__port is None:
-            self.__port = get_unused_port()
         return self.__port
 
     def get_protocol(self):
diff --git a/website/sphinx/releases/next.rst b/website/sphinx/releases/next.rst
index f4bd8cc0..e5f7ed04 100644
--- a/website/sphinx/releases/next.rst
+++ b/website/sphinx/releases/next.rst
@@ -30,3 +30,6 @@ In progress
 * Empty HTTP request arguments are no longer ignored.  This applies to
   ``HTTPRequest.arguments`` and ``RequestHandler.get_argument[s]``
   in WSGI and non-WSGI modes.
+* New function `tornado.testing.bind_unused_port` both chooses a port
+  and binds a socket to it, so there is no risk of another process
+  using the same port.  ``get_unused_port`` is now deprecated.
diff --git a/website/sphinx/testing.rst b/website/sphinx/testing.rst
index faf4ac7a..24f5c926 100644
--- a/website/sphinx/testing.rst
+++ b/website/sphinx/testing.rst
@@ -32,4 +32,6 @@
    Helper functions
    ----------------
 
+   .. autofunction:: bind_unused_port
+
    .. autofunction:: get_unused_port