diff --git a/Lib/test/test_ftplib.py b/Lib/test/test_ftplib.py
index 1a8e2f91d386df..462d5d6d4c4428 100644
--- a/Lib/test/test_ftplib.py
+++ b/Lib/test/test_ftplib.py
@@ -272,13 +272,15 @@ def start(self):
         self.__flag.wait()
 
     def run(self):
-        self.active = True
-        self.__flag.set()
-        while self.active and asyncore.socket_map:
-            self.active_lock.acquire()
-            asyncore.loop(timeout=0.1, count=1)
-            self.active_lock.release()
-        asyncore.close_all(ignore_all=True)
+        try:
+            self.active = True
+            self.__flag.set()
+            while self.active and asyncore.socket_map:
+                self.active_lock.acquire()
+                asyncore.loop(timeout=0.1, count=1)
+                self.active_lock.release()
+        finally:
+            self.close()
 
     def stop(self):
         assert self.active
@@ -464,20 +466,27 @@ class DummyTLS_FTPServer(DummyFTPServer):
         handler = DummyTLS_FTPHandler
 
 
+def setup_server(self, server):
+    self.server = server
+    self.server.start()
+
+    @self.addCleanup
+    def close_server():
+        self.server.stop()
+        # Explicitly clear the attribute to prevent dangling thread
+        self.server = None
+        asyncore.close_all(ignore_all=True)
+
+
 class TestFTPClass(TestCase):
 
     def setUp(self):
-        self.server = DummyFTPServer((HOST, 0))
-        self.server.start()
+        setup_server(self, DummyFTPServer((HOST, 0)))
         self.client = ftplib.FTP(timeout=TIMEOUT)
         self.client.connect(self.server.host, self.server.port)
 
     def tearDown(self):
         self.client.close()
-        self.server.stop()
-        # Explicitly clear the attribute to prevent dangling thread
-        self.server = None
-        asyncore.close_all(ignore_all=True)
 
     def check_data(self, received, expected):
         self.assertEqual(len(received), len(expected))
@@ -799,17 +808,12 @@ def test_storlines_too_long(self):
 class TestIPv6Environment(TestCase):
 
     def setUp(self):
-        self.server = DummyFTPServer((HOSTv6, 0), af=socket.AF_INET6)
-        self.server.start()
+        setup_server(self, DummyFTPServer((HOSTv6, 0), af=socket.AF_INET6))
         self.client = ftplib.FTP(timeout=TIMEOUT)
         self.client.connect(self.server.host, self.server.port)
 
     def tearDown(self):
         self.client.close()
-        self.server.stop()
-        # Explicitly clear the attribute to prevent dangling thread
-        self.server = None
-        asyncore.close_all(ignore_all=True)
 
     def test_af(self):
         self.assertEqual(self.client.af, socket.AF_INET6)
@@ -846,8 +850,7 @@ class TestTLS_FTPClassMixin(TestFTPClass):
     """
 
     def setUp(self):
-        self.server = DummyTLS_FTPServer((HOST, 0))
-        self.server.start()
+        setup_server(self, DummyTLS_FTPServer((HOST, 0)))
         self.client = ftplib.FTP_TLS(timeout=TIMEOUT)
         self.client.connect(self.server.host, self.server.port)
         # enable TLS
@@ -860,17 +863,12 @@ class TestTLS_FTPClass(TestCase):
     """Specific TLS_FTP class tests."""
 
     def setUp(self):
-        self.server = DummyTLS_FTPServer((HOST, 0))
-        self.server.start()
+        setup_server(self, DummyTLS_FTPServer((HOST, 0)))
         self.client = ftplib.FTP_TLS(timeout=TIMEOUT)
         self.client.connect(self.server.host, self.server.port)
 
     def tearDown(self):
         self.client.close()
-        self.server.stop()
-        # Explicitly clear the attribute to prevent dangling thread
-        self.server = None
-        asyncore.close_all(ignore_all=True)
 
     def test_control_connection(self):
         self.assertNotIsInstance(self.client.sock, ssl.SSLSocket)
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index e509188243f697..73c1f4f0add1e0 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -2586,13 +2586,15 @@ def wait(self):
     # --- internals
 
     def run(self):
-        self._active = True
-        self.__flag.set()
-        while self._active and asyncore.socket_map:
-            self._active_lock.acquire()
-            asyncore.loop(timeout=0.001, count=1)
-            self._active_lock.release()
-        asyncore.close_all()
+        try:
+            self._active = True
+            self.__flag.set()
+            while self._active and asyncore.socket_map:
+                self._active_lock.acquire()
+                asyncore.loop(timeout=0.001, count=1)
+                self._active_lock.release()
+        finally:
+            self.close()
 
     def handle_accept(self):
         conn, addr = self.accept()
@@ -2629,9 +2631,20 @@ def tearDownClass(cls):
         support.threading_cleanup(*cls.key)
         support.unlink(support.TESTFN)
 
-    def setUp(self):
-        self.server = SendfileTestServer((support.HOST, 0))
+    def setup_server(self, server):
+        self.server = server
         self.server.start()
+
+        @self.addCleanup
+        def close_server():
+            if self.server.running:
+                self.server.stop()
+            # Explicitly clear the attribute to prevent dangling thread
+            self.server = None
+            asyncore.close_all(ignore_all=True)
+
+    def setUp(self):
+        self.setup_server(SendfileTestServer((support.HOST, 0)))
         self.client = socket.socket()
         self.client.connect((self.server.host, self.server.port))
         self.client.settimeout(1)
@@ -2644,9 +2657,6 @@ def setUp(self):
     def tearDown(self):
         self.file.close()
         self.client.close()
-        if self.server.running:
-            self.server.stop()
-        self.server = None
 
     def sendfile_wrapper(self, sock, file, offset, nbytes, headers=[], trailers=[]):
         """A higher level wrapper representing how an application is
diff --git a/Lib/test/test_poplib.py b/Lib/test/test_poplib.py
index bf568bd77bffaf..6abdc93879395a 100644
--- a/Lib/test/test_poplib.py
+++ b/Lib/test/test_poplib.py
@@ -10,6 +10,7 @@
 import os
 import errno
 import threading
+import traceback
 
 from unittest import TestCase, skipUnless
 from test import support as test_support
@@ -220,18 +221,21 @@ def start(self):
         self.__flag.wait()
 
     def run(self):
-        self.active = True
-        self.__flag.set()
-        while self.active and asyncore.socket_map:
-            self.active_lock.acquire()
-            asyncore.loop(timeout=0.1, count=1)
-            self.active_lock.release()
-        asyncore.close_all(ignore_all=True)
+        try:
+            self.active = True
+            self.__flag.set()
+            while self.active and asyncore.socket_map:
+                self.active_lock.acquire()
+                asyncore.loop(timeout=0.1, count=1)
+                self.active_lock.release()
+        finally:
+            self.close()
 
     def stop(self):
         assert self.active
         self.active = False
         self.join()
+        asyncore.close_all(ignore_all=True)
 
     def handle_accepted(self, conn, addr):
         self.handler_instance = self.handler(conn)
@@ -251,16 +255,24 @@ class TestPOP3Class(TestCase):
     def assertOK(self, resp):
         self.assertTrue(resp.startswith(b"+OK"))
 
-    def setUp(self):
+    def setup_server(self, handler_class=None):
         self.server = DummyPOP3Server((HOST, PORT))
+        if handler_class is not None:
+            self.server.handler = handler_class
         self.server.start()
+
+        @self.addCleanup
+        def close_server():
+            self.server.stop()
+            # Explicitly clear the attribute to prevent dangling thread
+            self.server = None
+
+    def setUp(self):
+        self.setup_server()
         self.client = poplib.POP3(self.server.host, self.server.port, timeout=3)
 
     def tearDown(self):
         self.client.close()
-        self.server.stop()
-        # Explicitly clear the attribute to prevent dangling thread
-        self.server = None
 
     def test_getwelcome(self):
         self.assertEqual(self.client.getwelcome(),
@@ -400,9 +412,7 @@ class TestPOP3_SSLClass(TestPOP3Class):
     # repeat previous tests by using poplib.POP3_SSL
 
     def setUp(self):
-        self.server = DummyPOP3Server((HOST, PORT))
-        self.server.handler = DummyPOP3_SSLHandler
-        self.server.start()
+        self.setup_server(DummyPOP3_SSLHandler)
         self.client = poplib.POP3_SSL(self.server.host, self.server.port)
 
     def test__all__(self):
@@ -444,8 +454,7 @@ class TestPOP3_TLSClass(TestPOP3Class):
     # repeat previous tests by using poplib.POP3.stls()
 
     def setUp(self):
-        self.server = DummyPOP3Server((HOST, PORT))
-        self.server.start()
+        self.setup_server()
         self.client = poplib.POP3(self.server.host, self.server.port, timeout=3)
         self.client.stls()
 
@@ -458,9 +467,6 @@ def tearDown(self):
                 # response will be treated as response to QUIT and raise
                 # this exception
                 self.client.close()
-        self.server.stop()
-        # Explicitly clear the attribute to prevent dangling thread
-        self.server = None
 
     def test_stls(self):
         self.assertRaises(poplib.error_proto, self.client.stls)
diff --git a/Misc/NEWS.d/next/Library/2018-04-09-19-02-34.bpo-33099.Bgn7Kc.rst b/Misc/NEWS.d/next/Library/2018-04-09-19-02-34.bpo-33099.Bgn7Kc.rst
new file mode 100644
index 00000000000000..3748c1fa6699c6
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-04-09-19-02-34.bpo-33099.Bgn7Kc.rst
@@ -0,0 +1,2 @@
+Fix test_poplib hangs when an error occured in ``setUp()`` method or
+``DummyPOP3Server.run()``.