Fix port selection.

Author: jgosmann

nengo_gui/main.py

@@ -1,4 +1,5 @@
 import argparse
+import errno
 import logging
 import os.path
 import threading
@@ -29,7 +30,7 @@ def main():
         '--key', nargs=1, default=[None], type=str, help="SSL key file")
     parser.add_argument(
         '-P', '--port', dest='port', metavar='PORT',
-        default=8080, type=int, help='port to run server on')
+        type=int, help='port to run server on')
     parser.add_argument(
         'filename', nargs='?', type=str, help='initial file to load')
     parser.add_argument(
@@ -39,7 +40,8 @@ def main():
         default='nengo', type=str, help='default backend to use')
     parser.add_argument('--browser', dest='browser', action='store_true')
     parser.add_argument('--no-browser', dest='browser', action='store_false')
-    parser.add_argument('--auto-shutdown', nargs=1, type=float,
+    parser.add_argument(
+        '--auto-shutdown', nargs=1, type=float,
         help="Time limit before automatic shutdown. Set to 0 to deactivate.",
         default=[2])
     parser.set_defaults(browser=True)
@@ -50,20 +52,26 @@ def main():
     else:
         logging.basicConfig()
 
+    if args.port is None:
+        port = 8080
+    else:
+        port = args.port
+
     if args.password:
         if args.password is True:
             password = hashpw(prompt_pw(), gensalt())
         else:
             password = hashpw(args.password, gensalt())
         server_settings = GuiServerSettings(
-            ('', 8080), args.auto_shutdown[0], password_hash=password,
+            ('', port), args.auto_shutdown[0], password_hash=password,
             ssl_cert=args.cert[0], ssl_key=args.key[0])
         if not server_settings.use_ssl:
             raise ValueError("Password protection only allowed with SSL.")
     else:
         server_settings = GuiServerSettings(
-            ('localhost', 8080), args.auto_shutdown[0], ssl_cert=args.cert[0],
+            ('localhost', port), args.auto_shutdown[0], ssl_cert=args.cert[0],
             ssl_key=args.key[0])
+    host = server_settings.listen_addr[0]
 
     try:
         if args.filename is None:
@@ -72,9 +80,21 @@ def main():
         else:
             filename = args.filename
         page_settings = nengo_gui.page.PageSettings(backend=args.backend)
-        s = nengo_gui.gui.InteractiveGUI(
-            ModelContext(filename=filename), server_settings,
-            page_settings=page_settings)
+        s = None
+        while s is None:
+            try:
+                s = nengo_gui.gui.InteractiveGUI(
+                    ModelContext(filename=filename), server_settings,
+                    page_settings=page_settings)
+            except EnvironmentError as err:
+                if args.port is None and err.errno == errno.EADDRINUSE:
+                    port += 1
+                    if port > 0xFFFF:
+                        raise
+                    server_settings.listen_addr = (host, port)
+                else:
+                    raise
+
         s.server.auto_shutdown = args.auto_shutdown[0]
 
         if args.browser:
@@ -90,5 +110,6 @@ def main():
     finally:
         logging.shutdown()
 
+
 if __name__ == '__main__':
     main()