Added popenpoll.py example of using popen()/pmonitor()

examples/README

@@ -48,6 +48,11 @@ multitest.py:
 
 This example creates a network and runs multiple tests on it.
 
+popenpoll.py:
+
+This example demonstrates monitoring output from multiple hosts using
+the node.popen() interface (which returns Popen objects) and pmonitor().
+
 scratchnet.py, scratchnetuser.py:
 
 These two examples demonstrate how to create a network by using the lowest-

examples/popenpoll.py

@@ -0,0 +1,33 @@
+#!/usr/bin/python
+
+"Monitor multiple hosts using popen()/pmonitor()"
+
+from mininet.net import Mininet
+from mininet.topo import SingleSwitchTopo
+from mininet.util import pmonitor
+from time import time
+from signal import SIGINT
+
+def pmonitorTest( N=3, seconds=10 ):
+    "Run pings and monitor multiple hosts using pmonitor"
+    topo = SingleSwitchTopo( N )
+    net = Mininet( topo )
+    net.start()
+    hosts = net.hosts
+    print "Starting test..."
+    server = hosts[ 0 ]
+    popens = {}
+    for h in hosts:
+        popens[ h ] = h.popen('ping', server.IP() )
+        print "Monitoring output for", seconds, "seconds"
+        endTime = time() + seconds
+        for h, line in pmonitor( popens, timeoutms=500 ):
+            if h:
+                print '%s: %s' % ( h.name, line ),
+            if time() >= endTime:
+                for p in popens.values():
+                    p.send_signal( SIGINT )
+                net.stop()
+
+if __name__ == '__main__':
+    pmonitorTest()