=== modified file 'Lib/idlelib/PyShell.py'
--- Lib/idlelib/PyShell.py	2008-10-16 19:40:14 +0000
+++ Lib/idlelib/PyShell.py	2008-12-01 23:10:04 +0000
@@ -342,17 +342,21 @@
         InteractiveInterpreter.__init__(self, locals=locals)
         self.save_warnings_filters = None
         self.restarting = False
-        self.subprocess_arglist = self.build_subprocess_arglist()
+        self.subprocess_arglist = None
+        self.port = None
 
-    port = 8833
     rpcclt = None
     rpcpid = None
 
     def spawn_subprocess(self):
+        if self.subprocess_arglist==None:
+            self.subprocess_arglist = self.build_subprocess_arglist()
         args = self.subprocess_arglist
         self.rpcpid = os.spawnv(os.P_NOWAIT, sys.executable, args)
 
     def build_subprocess_arglist(self):
+        assert (self.port!=0 and self.port!=None), (
+            "Socket should have been assigned a port number.")
         w = ['-W' + s for s in sys.warnoptions]
         if 1/2 > 0: # account for new division
             w.append('-Qnew')
@@ -373,21 +377,19 @@
         return [decorated_exec] + w + ["-c", command, str(self.port)]
 
     def start_subprocess(self):
-        # spawning first avoids passing a listening socket to the subprocess
-        self.spawn_subprocess()
-        #time.sleep(20) # test to simulate GUI not accepting connection
-        addr = (LOCALHOST, self.port)
+        addr = (LOCALHOST, 0)
         # Idle starts listening for connection on localhost
-        for i in range(3):
-            time.sleep(i)
-            try:
-                self.rpcclt = MyRPCClient(addr)
-                break
-            except socket.error, err:
-                pass
-        else:
+        try:
+            self.rpcclt = MyRPCClient(addr)
+        except socket.error, err:
             self.display_port_binding_error()
             return None
+        self.port=self.rpcclt.listening_sock.getsockname()[1]
+        # Spawning second means we pass a listening socket to the
+        # subprocess, which isn't ideal, but otherwise we don't know
+        # what port the socket got assigned to.
+        self.spawn_subprocess()
+        #time.sleep(20) # test to simulate GUI not accepting connection
         # Accept the connection from the Python execution server
         self.rpcclt.listening_sock.settimeout(10)
         try:
@@ -754,10 +756,10 @@
     def display_port_binding_error(self):
         tkMessageBox.showerror(
             "Port Binding Error",
-            "IDLE can't bind TCP/IP port 8833, which is necessary to "
-            "communicate with its Python execution server.  Either "
-            "no networking is installed on this computer or another "
-            "process (another IDLE?) is using the port.  Run IDLE with the -n "
+            "IDLE can't bind to a TCP/IP port, which is necessary to "
+            "communicate with its Python execution server.  This might be "
+            "because no networking is installed on this computer.  "
+            "Run IDLE with the -n "
             "command line switch to start without a subprocess and refer to "
             "Help/IDLE Help 'Running without a subprocess' for further "
             "details.",

=== modified file 'Lib/idlelib/rpc.py'
--- Lib/idlelib/rpc.py	2008-05-25 07:20:14 +0000
+++ Lib/idlelib/rpc.py	2008-12-01 23:29:03 +0000
@@ -518,8 +518,6 @@
 
     def __init__(self, address, family=socket.AF_INET, type=socket.SOCK_STREAM):
         self.listening_sock = socket.socket(family, type)
-        self.listening_sock.setsockopt(socket.SOL_SOCKET,
-                                       socket.SO_REUSEADDR, 1)
         self.listening_sock.bind(address)
         self.listening_sock.listen(1)