Copying mininet_p4 from behavioral-model repo (#86)

Updating the P4Switch class to use different mechanism
for checking when the switch is listening on the Thrift
port. This might fix an issues where Mininet hangs on
start.

P4D2_2017_Fall/utils/netstat.py

@@ -0,0 +1,21 @@
+# Copyright 2017-present Open Networking Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import psutil
+def check_listening_on_port(port):
+    for c in psutil.net_connections(kind='inet'):
+        if c.status == 'LISTEN' and c.laddr[1] == port:
+            return True
+    return False