diff --git a/apps/foo/src/main/java/org/onlab/onos/foo/IOLoopTestClient.java b/apps/foo/src/main/java/org/onlab/onos/foo/IOLoopTestClient.java
index 29a1904..ebbe5bc 100644
--- a/apps/foo/src/main/java/org/onlab/onos/foo/IOLoopTestClient.java
+++ b/apps/foo/src/main/java/org/onlab/onos/foo/IOLoopTestClient.java
@@ -298,7 +298,7 @@
             List<TestMessage> batch = Lists.newArrayListWithCapacity(size);
             for (int i = 0; i < size; i++) {
                 batch.add(new TestMessage(msgLength, currentTimeMillis(), 0,
-                                          this.stream.padding(msgLength)));
+                                          stream.padding()));
             }
             acquire(size);
             stream.write(batch);
diff --git a/apps/foo/src/main/java/org/onlab/onos/foo/IOLoopTestServer.java b/apps/foo/src/main/java/org/onlab/onos/foo/IOLoopTestServer.java
index bb5fee7..778f217 100644
--- a/apps/foo/src/main/java/org/onlab/onos/foo/IOLoopTestServer.java
+++ b/apps/foo/src/main/java/org/onlab/onos/foo/IOLoopTestServer.java
@@ -85,10 +85,12 @@
         IOLoopTestServer server = new IOLoopTestServer(ip, wc, ml, PORT);
         server.start();
 
-        // Start pruning clients.
-        while (true) {
+        // Start pruning clients and keep going until their number goes to 0.
+        int remaining = -1;
+        while (remaining == -1 || remaining > 0) {
             delay(PRUNE_FREQUENCY);
-            server.prune();
+            int r = server.prune();
+            remaining = remaining == -1 && r == 0 ? remaining : r;
         }
     }
 
@@ -161,11 +163,15 @@
 
     /**
      * Prunes the IO loops of stale message buffers.
+     *
+     * @return number of remaining IO loops among all workers.
      */
-    public void prune() {
+    public int prune() {
+        int count = 0;
         for (CustomIOLoop l : iloops) {
-            l.pruneStaleStreams();
+            count += l.pruneStaleStreams();
         }
+        return count;
     }
 
     // Get the next worker to which a client should be assigned
diff --git a/apps/foo/src/main/java/org/onlab/onos/foo/TestIOClientCommand.java b/apps/foo/src/main/java/org/onlab/onos/foo/TestIOClientCommand.java
index 52128e3..612d320 100644
--- a/apps/foo/src/main/java/org/onlab/onos/foo/TestIOClientCommand.java
+++ b/apps/foo/src/main/java/org/onlab/onos/foo/TestIOClientCommand.java
@@ -1,5 +1,6 @@
 package org.onlab.onos.foo;
 
+import org.apache.karaf.shell.commands.Argument;
 import org.apache.karaf.shell.commands.Command;
 import org.onlab.onos.cli.AbstractShellCommand;
 
@@ -12,12 +13,32 @@
          description = "Starts the test IO loop client")
 public class TestIOClientCommand extends AbstractShellCommand {
 
+    @Argument(index = 0, name = "serverIp", description = "Server IP address",
+              required = false, multiValued = false)
+    String serverIp = "127.0.0.1";
+
+    @Argument(index = 1, name = "workers", description = "IO workers",
+              required = false, multiValued = false)
+    String workers = "6";
+
+    @Argument(index = 2, name = "messageCount", description = "Message count",
+              required = false, multiValued = false)
+    String messageCount = "10000000";
+
+    @Argument(index = 3, name = "messageLength", description = "Message length (bytes)",
+              required = false, multiValued = false)
+    String messageLength = "128";
+
+    @Argument(index = 4, name = "timeoutSecs", description = "Test timeout (seconds)",
+              required = false, multiValued = false)
+    String timeoutSecs = "30";
+
     @Override
     protected void execute() {
         try {
-            startStandalone(new String[]{});
+            startStandalone(new String[]{serverIp, workers, messageCount, messageLength, timeoutSecs});
         } catch (Exception e) {
-            error("Unable to start server %s", e);
+            error("Unable to start client %s", e);
         }
     }
 
diff --git a/apps/foo/src/main/java/org/onlab/onos/foo/TestIOServerCommand.java b/apps/foo/src/main/java/org/onlab/onos/foo/TestIOServerCommand.java
index 313141d..4777e71 100644
--- a/apps/foo/src/main/java/org/onlab/onos/foo/TestIOServerCommand.java
+++ b/apps/foo/src/main/java/org/onlab/onos/foo/TestIOServerCommand.java
@@ -1,11 +1,11 @@
 package org.onlab.onos.foo;
 
+import org.apache.karaf.shell.commands.Argument;
 import org.apache.karaf.shell.commands.Command;
 import org.onlab.onos.cli.AbstractShellCommand;
 
 import static org.onlab.onos.foo.IOLoopTestServer.startStandalone;
 
-
 /**
  * Starts the test IO loop server.
  */
@@ -13,10 +13,22 @@
          description = "Starts the test IO loop server")
 public class TestIOServerCommand extends AbstractShellCommand {
 
+    @Argument(index = 0, name = "serverIp", description = "Server IP address",
+              required = false, multiValued = false)
+    String serverIp = "127.0.0.1";
+
+    @Argument(index = 1, name = "workers", description = "IO workers",
+              required = false, multiValued = false)
+    String workers = "6";
+
+    @Argument(index = 2, name = "messageLength", description = "Message length (bytes)",
+              required = false, multiValued = false)
+    String messageLength = "128";
+
     @Override
     protected void execute() {
         try {
-            startStandalone(new String[]{});
+            startStandalone(new String[]{serverIp, workers, messageLength});
         } catch (Exception e) {
             error("Unable to start server %s", e);
         }
diff --git a/apps/foo/src/main/java/org/onlab/onos/foo/TestMessageStream.java b/apps/foo/src/main/java/org/onlab/onos/foo/TestMessageStream.java
index a7a3e6a..0ed9e8d 100644
--- a/apps/foo/src/main/java/org/onlab/onos/foo/TestMessageStream.java
+++ b/apps/foo/src/main/java/org/onlab/onos/foo/TestMessageStream.java
@@ -6,6 +6,7 @@
 import java.nio.ByteBuffer;
 import java.nio.channels.ByteChannel;
 
+import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkState;
 
 /**
@@ -19,12 +20,18 @@
     private static final int META_LENGTH = 40;
 
     private final int length;
+    private boolean isStrict = true;
 
     public TestMessageStream(int length, ByteChannel ch, IOLoop<TestMessage, ?> loop) {
         super(loop, ch, 64 * 1024, 500);
+        checkArgument(length >= META_LENGTH, "Length must be greater than header length of 40");
         this.length = length;
     }
 
+    void setNonStrict() {
+        isStrict = false;
+    }
+
     @Override
     protected TestMessage read(ByteBuffer rb) {
         if (rb.remaining() < length) {
@@ -32,16 +39,20 @@
         }
 
         long startTag = rb.getLong();
-        checkState(startTag == START_TAG, "Incorrect message start");
+        if (isStrict) {
+            checkState(startTag == START_TAG, "Incorrect message start");
+        }
 
         long size = rb.getLong();
         long requestorTime = rb.getLong();
         long responderTime = rb.getLong();
-        byte[] padding = padding(length);
+        byte[] padding = padding();
         rb.get(padding);
 
         long endTag = rb.getLong();
-        checkState(endTag == END_TAG, "Incorrect message end");
+        if (isStrict) {
+            checkState(endTag == END_TAG, "Incorrect message end");
+        }
 
         return new TestMessage((int) size, requestorTime, responderTime, padding);
     }
@@ -60,7 +71,7 @@
         wb.putLong(END_TAG);
     }
 
-    public byte[] padding(int msgLength) {
-        return new byte[msgLength - META_LENGTH];
+    public byte[] padding() {
+        return new byte[length - META_LENGTH];
     }
 }
diff --git a/utils/nio/src/main/java/org/onlab/nio/IOLoop.java b/utils/nio/src/main/java/org/onlab/nio/IOLoop.java
index 94cd688..1309330 100644
--- a/utils/nio/src/main/java/org/onlab/nio/IOLoop.java
+++ b/utils/nio/src/main/java/org/onlab/nio/IOLoop.java
@@ -259,13 +259,16 @@
 
     /**
      * Prunes the registered streams by discarding any stale ones.
+     *
+     * @return number of remaining streams
      */
-    public synchronized void pruneStaleStreams() {
+    public synchronized int pruneStaleStreams() {
         for (MessageStream<M> stream : streams) {
             if (stream.isStale()) {
                 stream.close();
             }
         }
+        return streams.size();
     }
 
 }