stoppign starting works nicely

 package org.onlab.onos.of.drivers.impl;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -135,7 +136,7 @@ public class OFSwitchImplOVS13 extends AbstractOpenFlowSwitch {
 
     @Override
     public void write(OFMessage msg) {
-        channel.write(msg);
+        channel.write(Collections.singletonList(msg));
 
     }
 

@@ -14,6 +14,7 @@ import org.apache.felix.scr.annotations.Deactivate;
 import org.apache.felix.scr.annotations.Reference;
 import org.apache.felix.scr.annotations.ReferenceCardinality;
 import org.onlab.onos.net.Device;
+import org.onlab.onos.net.DeviceId;
 import org.onlab.onos.net.MastershipRole;
 import org.onlab.onos.net.PortNumber;
 import org.onlab.onos.net.device.DefaultDeviceDescription;
@@ -66,14 +67,22 @@ public class OpenFlowDeviceProvider extends AbstractProvider implements DevicePr
     public void activate() {
         providerService = providerRegistry.register(this);
         controller.addListener(listener);
+        for (OpenFlowSwitch sw : controller.getSwitches()) {
+            listener.switchAdded(new Dpid(sw.getId()));
+        }
         LOG.info("Started");
     }
 
     @Deactivate
     public void deactivate() {
+        for (OpenFlowSwitch sw : controller.getSwitches()) {
+            providerService.deviceDisconnected(DeviceId.deviceId("of:"
+                    + Long.toHexString(sw.getId())));
+        }
         providerRegistry.unregister(this);
         controller.removeListener(listener);
         providerService = null;
+
         LOG.info("Stopped");
     }
 

@@ -86,6 +86,7 @@ public class LinkDiscovery implements TimerTask {
     private final OpenFlowController ctrl;
     private final LinkProviderService linkProvider;
     private final Map<Integer, OFPortDesc> ports;
+    private Timeout timeout;
 
     /**
      * Instantiates discovery manager for the given physical switch. Creates a
@@ -127,7 +128,7 @@ public class LinkDiscovery implements TimerTask {
                 addPort(port);
             }
         }
-        Timer.getTimer().newTimeout(this, this.probeRate,
+        timeout = Timer.getTimer().newTimeout(this, this.probeRate,
                 TimeUnit.MILLISECONDS);
         this.log.debug("Started discovery manager for switch {}",
                 sw.getId());
@@ -186,6 +187,10 @@ public class LinkDiscovery implements TimerTask {
                         portnum);
             }
         }
+        ConnectPoint cp = new ConnectPoint(
+                DeviceId.deviceId("of:" + Long.toHexString(sw.getId())),
+                PortNumber.portNumber(port.getPortNo().getPortNumber()));
+        linkProvider.linksVanished(cp);
 
     }
 
@@ -380,14 +385,19 @@ public class LinkDiscovery implements TimerTask {
         }
 
         // reschedule timer
-        Timer.getTimer().newTimeout(this, this.probeRate,
+        timeout = Timer.getTimer().newTimeout(this, this.probeRate,
                 TimeUnit.MILLISECONDS);
     }
 
     public void removeAllPorts() {
-        for (OFPortDesc port : sw.getPorts()) {
+        for (OFPortDesc port : ports.values()) {
             removePort(port);
         }
     }
 
+    public void stop() {
+        removeAllPorts();
+        timeout.cancel();
+    }
+
 }

@@ -10,9 +10,7 @@ import org.apache.felix.scr.annotations.Component;
 import org.apache.felix.scr.annotations.Deactivate;
 import org.apache.felix.scr.annotations.Reference;
 import org.apache.felix.scr.annotations.ReferenceCardinality;
-import org.onlab.onos.net.ConnectPoint;
 import org.onlab.onos.net.DeviceId;
-import org.onlab.onos.net.PortNumber;
 import org.onlab.onos.net.link.LinkProvider;
 import org.onlab.onos.net.link.LinkProviderRegistry;
 import org.onlab.onos.net.link.LinkProviderService;
@@ -20,10 +18,10 @@ import org.onlab.onos.net.provider.AbstractProvider;
 import org.onlab.onos.net.provider.ProviderId;
 import org.onlab.onos.of.controller.Dpid;
 import org.onlab.onos.of.controller.OpenFlowController;
+import org.onlab.onos.of.controller.OpenFlowSwitch;
 import org.onlab.onos.of.controller.OpenFlowSwitchListener;
 import org.onlab.onos.of.controller.PacketContext;
 import org.onlab.onos.of.controller.PacketListener;
-import org.onlab.timer.Timer;
 import org.projectfloodlight.openflow.protocol.OFPortConfig;
 import org.projectfloodlight.openflow.protocol.OFPortDesc;
 import org.projectfloodlight.openflow.protocol.OFPortState;
@@ -51,6 +49,8 @@ public class OpenFlowLinkProvider extends AbstractProvider implements LinkProvid
 
     private final InternalLinkProvider listener = new InternalLinkProvider();
 
+    private final Map<Dpid, LinkDiscovery> discoverers = new ConcurrentHashMap<>();
+
     /**
      * Creates an OpenFlow link provider.
      */
@@ -63,23 +63,28 @@ public class OpenFlowLinkProvider extends AbstractProvider implements LinkProvid
         providerService = providerRegistry.register(this);
         controller.addListener(listener);
         controller.addPacketListener(0, listener);
+        for (OpenFlowSwitch sw : controller.getSwitches()) {
+            listener.switchAdded(new Dpid(sw.getId()));
+        }
         log.info("Started");
     }
 
     @Deactivate
     public void deactivate() {
+        for (LinkDiscovery ld : discoverers.values()) {
+            ld.stop();
+        }
         providerRegistry.unregister(this);
         controller.removeListener(listener);
         controller.removePacketListener(listener);
         providerService = null;
-        Timer.getTimer().stop();
+
         log.info("Stopped");
     }
 
 
     private class InternalLinkProvider implements PacketListener, OpenFlowSwitchListener {
 
-        private final Map<Dpid, LinkDiscovery> discoverers = new ConcurrentHashMap<>();
 
         @Override
         public void handlePacket(PacketContext pktCtx) {
@@ -102,7 +107,7 @@ public class OpenFlowLinkProvider extends AbstractProvider implements LinkProvid
 
         @Override
         public void switchRemoved(Dpid dpid) {
-            LinkDiscovery ld = this.discoverers.remove(dpid);
+            LinkDiscovery ld = discoverers.remove(dpid);
             if (ld != null) {
                 ld.removeAllPorts();
             }
@@ -122,10 +127,9 @@ public class OpenFlowLinkProvider extends AbstractProvider implements LinkProvid
             if (enabled) {
                 ld.addPort(port);
             } else {
-                ConnectPoint cp = new ConnectPoint(
-                        DeviceId.deviceId("of:" + Long.toHexString(dpid.value())),
-                        PortNumber.portNumber(port.getPortNo().getPortNumber()));
-                providerService.linksVanished(cp);
+                /*
+                 * remove port calls linkVanished
+                 */
                 ld.removePort(port);
             }