Allow the OS to select a free port for each test server. For

DebuggingServerTests, construct SMTP objects with a localhost argument
to avoid abysmally long FQDN lookups (not relevant to items under
test) on some machines that would cause the test to fail. Moved server
setup code in the server function inside the try block to avoid the
possibility of setup failure hanging the test.  Minor edits to conform
to PEP 8. [GSoC - Alan McIntyre]

Lib/test/test_smtplib.py

@@ -11,21 +11,25 @@ import select
 from unittest import TestCase
 from test import test_support
 
+# PORT is used to communicate the port number assigned to the server
+# to the test client
 HOST = "localhost"
-PORT = 54328
+PORT = None
 
 def server(evt, buf):
-    serv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-    serv.settimeout(3)
-    serv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
-    serv.bind(("", PORT))
-    serv.listen(5)
     try:
+        serv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        serv.settimeout(3)
+        serv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        serv.bind(("", 0))
+        global PORT
+        PORT = serv.getsockname()[1]
+        serv.listen(5)
         conn, addr = serv.accept()
     except socket.timeout:
         pass
     else:
-        n = 200
+        n = 500
         while buf and n > 0:
             r, w, e = select.select([], [conn], [])
             if w:
@@ -38,6 +42,7 @@ def server(evt, buf):
         conn.close()
     finally:
         serv.close()
+        PORT = None
         evt.set()
 
 class GeneralTests(TestCase):
@@ -46,7 +51,16 @@ class GeneralTests(TestCase):
         self.evt = threading.Event()
         servargs = (self.evt, "220 Hola mundo\n")
         threading.Thread(target=server, args=servargs).start()
-        time.sleep(.1)
+
+        # wait until server thread has assigned a port number
+        n = 500
+        while PORT is None and n > 0:
+            time.sleep(0.01)
+            n -= 1
+
+        # wait a little longer (sometimes connections are refused
+        # on slow machines without this additional wait)
+        time.sleep(0.5)
 
     def tearDown(self):
         self.evt.wait()
@@ -69,7 +83,8 @@ class GeneralTests(TestCase):
 
     def testNonnumericPort(self):
         # check that non-numeric port raises ValueError
-        self.assertRaises(socket.error, smtplib.SMTP, "localhost", "bogus")
+        self.assertRaises(socket.error, smtplib.SMTP,
+                          "localhost", "bogus")
 
     def testTimeoutDefault(self):
         # default
@@ -96,61 +111,104 @@ class GeneralTests(TestCase):
 
 
 # Test server using smtpd.DebuggingServer
-def debugging_server(evt):
-    serv = smtpd.DebuggingServer(("", PORT), ('nowhere', -1))
+def debugging_server(serv_evt, client_evt):
+    serv = smtpd.DebuggingServer(("", 0), ('nowhere', -1))
+    global PORT
+    PORT = serv.getsockname()[1]
 
     try:
-        asyncore.loop(timeout=.01, count=300)
+        if hasattr(select, 'poll'):
+            poll_fun = asyncore.poll2
+        else:
+            poll_fun = asyncore.poll
+
+        n = 1000
+        while asyncore.socket_map and n > 0:
+            poll_fun(0.01, asyncore.socket_map)
+
+            # when the client conversation is finished, it will
+            # set client_evt, and it's then ok to kill the server
+            if client_evt.isSet():
+                serv.close()
+                break
+
+            n -= 1
+
     except socket.timeout:
         pass
     finally:
         # allow some time for the client to read the result
         time.sleep(0.5)
+        serv.close()
         asyncore.close_all()
-        evt.set()
+        PORT = None
+        time.sleep(0.5)
+        serv_evt.set()
 
 MSG_BEGIN = '---------- MESSAGE FOLLOWS ----------\n'
 MSG_END = '------------ END MESSAGE ------------\n'
 
 # Test behavior of smtpd.DebuggingServer
+# NOTE: the SMTP objects are created with a non-default local_hostname
+# argument to the constructor, since (on some systems) the FQDN lookup
+# caused by the default local_hostname sometimes takes so long that the
+# test server times out, causing the test to fail.
 class DebuggingServerTests(TestCase):
 
     def setUp(self):
+        # temporarily replace sys.stdout to capture DebuggingServer output
         self.old_stdout = sys.stdout
         self.output = StringIO.StringIO()
         sys.stdout = self.output
 
-        self.evt = threading.Event()
-        threading.Thread(target=debugging_server, args=(self.evt,)).start()
-        time.sleep(.5)
+        self.serv_evt = threading.Event()
+        self.client_evt = threading.Event()
+        serv_args = (self.serv_evt, self.client_evt)
+        threading.Thread(target=debugging_server, args=serv_args).start()
+
+        # wait until server thread has assigned a port number
+        n = 500
+        while PORT is None and n > 0:
+            time.sleep(0.01)
+            n -= 1
+
+        # wait a little longer (sometimes connections are refused
+        # on slow machines without this additional wait)
+        time.sleep(0.5)
 
     def tearDown(self):
-        self.evt.wait()
+        # indicate that the client is finished
+        self.client_evt.set()
+        # wait for the server thread to terminate
+        self.serv_evt.wait()
+        # restore sys.stdout
         sys.stdout = self.old_stdout
 
     def testBasic(self):
         # connect
-        smtp = smtplib.SMTP(HOST, PORT)
-        smtp.sock.close()
+        smtp = smtplib.SMTP(HOST, PORT, local_hostname='localhost', timeout=3)
+        smtp.quit()
 
     def testEHLO(self):
-        smtp = smtplib.SMTP(HOST, PORT)
-        self.assertEqual(smtp.ehlo(), (502, 'Error: command "EHLO" not implemented'))
-        smtp.sock.close()
+        smtp = smtplib.SMTP(HOST, PORT, local_hostname='localhost', timeout=3)
+        expected = (502, 'Error: command "EHLO" not implemented')
+        self.assertEqual(smtp.ehlo(), expected)
+        smtp.quit()
 
     def testHELP(self):
-        smtp = smtplib.SMTP(HOST, PORT)
+        smtp = smtplib.SMTP(HOST, PORT, local_hostname='localhost', timeout=3)
         self.assertEqual(smtp.help(), 'Error: command "HELP" not implemented')
-        smtp.sock.close()
+        smtp.quit()
 
     def testSend(self):
         # connect and send mail
         m = 'A test message'
-        smtp = smtplib.SMTP(HOST, PORT)
+        smtp = smtplib.SMTP(HOST, PORT, local_hostname='localhost', timeout=3)
         smtp.sendmail('John', 'Sally', m)
-        smtp.sock.close()
+        smtp.quit()
 
-        self.evt.wait()
+        self.client_evt.set()
+        self.serv_evt.wait()
         self.output.flush()
         mexpect = '%s%s\n%s' % (MSG_BEGIN, m, MSG_END)
         self.assertEqual(self.output.getvalue(), mexpect)
@@ -166,17 +224,28 @@ class BadHELOServerTests(TestCase):
         self.evt = threading.Event()
         servargs = (self.evt, "199 no hello for you!\n")
         threading.Thread(target=server, args=servargs).start()
-        time.sleep(.5)
+
+        # wait until server thread has assigned a port number
+        n = 500
+        while PORT is None and n > 0:
+            time.sleep(0.01)
+            n -= 1
+
+        # wait a little longer (sometimes connections are refused
+        # on slow machines without this additional wait)
+        time.sleep(0.5)
 
     def tearDown(self):
         self.evt.wait()
         sys.stdout = self.old_stdout
 
     def testFailingHELO(self):
-        self.assertRaises(smtplib.SMTPConnectError, smtplib.SMTP, HOST, PORT)
+        self.assertRaises(smtplib.SMTPConnectError, smtplib.SMTP,
+                            HOST, PORT, 'localhost', 3)
 
 def test_main(verbose=None):
-    test_support.run_unittest(GeneralTests, DebuggingServerTests, BadHELOServerTests)
+    test_support.run_unittest(GeneralTests, DebuggingServerTests,
+                              BadHELOServerTests)
 
 if __name__ == '__main__':
     test_main()