Updated the mechanism to select test server ports to remove a source

of intermittent test failures.  In ConnectionTests, a random port was
selected without checking if it was in use.  testZEO.get_port (moved
to forker) picked a random port, checking if it was in use, but
clients actually used that port *and* the following one.  Now check
that the returned and subsequent ports are free. (Of course, they
could get used betweed the time they're selected and the time they are
used by the test. Oh well.

src/ZEO/tests/ConnectionTests.py

@@ -158,8 +158,7 @@ class CommonSetupTearDown(StorageTestBase):
         self.addr.append(self._getAddr())
 
     def _getAddr(self):
-        # port+1 is also used, so only draw even port numbers
-        return 'localhost', random.randrange(25000, 30000, 2)
+        return 'localhost', forker.get_port()
 
     def getConfig(self, path, create, read_only):
         raise NotImplementedError

src/ZEO/tests/forker.py

@@ -14,6 +14,7 @@
 """Library for forking storage server and connecting client storage"""
 
 import os
+import random
 import sys
 import time
 import errno
@@ -201,3 +202,29 @@ def shutdown_zeo_server(adminaddr):
             ack = 'no ack received'
         logger.debug('shutdown_zeo_server(): acked: %s' % ack)
         s.close()
+
+def get_port():
+    """Return a port that is not in use.
+
+    Checks if a port is in use by trying to connect to it.  Assumes it
+    is not in use if connect raises an exception. We actually look for
+    2 consective free ports because most of the clients of this
+    function will use the returned port and the next one.
+
+    Raises RuntimeError after 10 tries.
+    """
+    for i in range(10):
+        port = random.randrange(20000, 30000)
+        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        s1 = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        try:
+            try:
+                s.connect(('localhost', port))
+                s1.connect(('localhost', port+1))
+            except socket.error:
+                # Perhaps we should check value of error too.
+                return port
+        finally:
+            s.close()
+            s1.close()
+    raise RuntimeError("Can't find port")

src/ZEO/tests/testZEO.py

@@ -18,9 +18,7 @@ import asyncore
 import doctest
 import logging
 import os
-import random
 import signal
-import socket
 import stat
 import tempfile
 import threading
@@ -50,6 +48,7 @@ from ZEO.ClientStorage import ClientStorage
 import ZEO.zrpc.connection
 
 from ZEO.tests import forker, Cache, CommitLockTests, ThreadTests
+from ZEO.tests.forker import get_port
 
 import ZEO.tests.ConnectionTests
 
@@ -128,27 +127,6 @@ class MiscZEOTests:
         finally:
             storage2.close()
 
-def get_port():
-    """Return a port that is not in use.
-
-    Checks if a port is in use by trying to connect to it.  Assumes it
-    is not in use if connect raises an exception.
-
-    Raises RuntimeError after 10 tries.
-    """
-    for i in range(10):
-        port = random.randrange(20000, 30000)
-        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-        try:
-            try:
-                s.connect(('localhost', port))
-            except socket.error:
-                # Perhaps we should check value of error too.
-                return port
-        finally:
-            s.close()
-    raise RuntimeError("Can't find port")
-
 class GenericTests(
     # Base class for all ZODB tests
     StorageTestBase.StorageTestBase,