Index: PyShell.py
===================================================================
--- PyShell.py	(revision 50822)
+++ PyShell.py	(working copy)
@@ -7,6 +7,7 @@
 import getopt
 import re
 import socket
+import select
 import time
 import threading
 import traceback
@@ -339,14 +340,13 @@
         InteractiveInterpreter.__init__(self, locals=locals)
         self.save_warnings_filters = None
         self.restarting = False
-        self.subprocess_arglist = self.build_subprocess_arglist()
 
-    port = 8833
+    port = None
     rpcclt = None
     rpcpid = None
 
     def spawn_subprocess(self):
-        args = self.subprocess_arglist
+        args = self.build_subprocess_arglist()
         self.rpcpid = os.spawnv(os.P_NOWAIT, sys.executable, args)
 
     def build_subprocess_arglist(self):
@@ -367,29 +367,57 @@
             decorated_exec = sys.executable
         return [decorated_exec] + w + ["-c", command, str(self.port)]
 
+    timeout = 10 # seconds
+    max_timeouts = 2
+    max_ports_to_try = 10
+    
+    ports = range(49152, 65536) # 'dynamic' ports as described by the DCCP
+                                # http://www.iana.org/assignments/port-numbers
+    # Bad ports taken from:
+    # http://www.doshelp.com/Ports/Trojan_Ports.htm
+    # http://www.simovits.com/trojans/trojans.html
+    bad_ports = [49301, 49683, 49698, 50000, 50005, 50021, 50130, 50505, 50551,
+                 50552, 50766, 50776, 50829, 51234, 51435, 51966, 52365, 52901,
+                 53001, 54283, 54320, 54321, 55165, 55555, 55665, 55666, 56565,
+                 57163, 57341, 57785, 58008, 58009, 58134, 58339, 58666, 59211,
+                 60000, 60001, 60006, 60008, 60068, 60411, 60551, 60552, 60666,
+                 61000, 61115, 61337, 61348, 61440, 61466, 61603, 61746, 61747,
+                 61748, 61979, 62011, 63485, 63808, 63809, 64101, 64429, 65000,
+                 65289, 65421, 65422, 65432, 65506, 65530, 65535]
+    ports = filter(lambda p,bps=bad_ports:p not in bps, ports)
+    import random
+    random.shuffle(ports)
+    ports = ports[:max_ports_to_try]
+
     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)
-        # Idle starts listening for connection on localhost
-        for i in range(3):
-            time.sleep(i)
+        timeouts = 0
+        for p in self.ports:
+            # IDLE starts listening for connection on localhost
+            addr = (LOCALHOST, p)
             try:
                 self.rpcclt = MyRPCClient(addr)
-                break
             except socket.error, err:
-                pass
+                continue
+            self.port = p
+            self.spawn_subprocess()
+            
+            # Accept the connection from the Python execution server
+            r,w,e = select.select([self.rpcclt.listening_sock], [], [],
+                                  self.timeout)
+            if not r:
+                self.rpcclt.listening_sock.close()
+                self.unix_terminate()
+                timeouts = timeouts + 1
+                if timeouts >= self.max_timeouts:
+                    self.display_no_subprocess_error()
+                    return None
+                continue
+            self.rpcclt.accept()
+            break
         else:
             self.display_port_binding_error()
             return None
-        # Accept the connection from the Python execution server
-        self.rpcclt.listening_sock.settimeout(10)
-        try:
-            self.rpcclt.accept()
-        except socket.timeout, err:
-            self.display_no_subprocess_error()
-            return None
+        
         self.rpcclt.register("stdin", self.tkconsole)
         self.rpcclt.register("stdout", self.tkconsole.stdout)
         self.rpcclt.register("stderr", self.tkconsole.stderr)
@@ -419,11 +447,12 @@
         was_executing = console.executing
         console.executing = False
         self.spawn_subprocess()
-        try:
-            self.rpcclt.accept()
-        except socket.timeout, err:
+        r,w,e = select.select([self.rpcclt.listening_sock], [], [],
+                              self.timeout)
+        if not r:
             self.display_no_subprocess_error()
             return None
+        self.rpcclt.accept()
         self.transfer_path()
         # annotate restart in shell window and mark it
         console.text.delete("iomark", "end-1c")
@@ -593,7 +622,7 @@
                 source = source.encode(IOBinding.encoding)
             except UnicodeError:
                 self.tkconsole.resetoutput()
-                self.write("Unsupported characters in input")
+                self.write("Unsupported characters in input\n")
                 return
         try:
             # InteractiveInterpreter.runsource() calls its runcode() method,
@@ -735,13 +764,13 @@
     def display_port_binding_error(self):
         tkMessageBox.showerror(
             "Port Binding Error",
-            "IDLE can't bind TCP/IP port 8833, which is necessary to "
+            "IDLE can't bind any TCP/IP port, 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 "
-            "command line switch to start without a subprocess and refer to "
-            "Help/IDLE Help 'Running without a subprocess' for further "
-            "details.",
+            "no networking is installed on this computer or IDLE is being "
+            "blocked from binding a port. Try again, or 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.",
             master=self.tkconsole.text)
 
     def display_no_subprocess_error(self):