diff --git a/utils/nio/src/test/java/org/onlab/nio/IOLoopClient.java b/utils/nio/src/test/java/org/onlab/nio/IOLoopClient.java
new file mode 100644
index 0000000..2497e0e
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+++ b/utils/nio/src/test/java/org/onlab/nio/IOLoopClient.java
@@ -0,0 +1,294 @@
+package org.onlab.nio;
+
+import org.onlab.util.Counter;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.SocketAddress;
+import java.nio.channels.ByteChannel;
+import java.nio.channels.SelectionKey;
+import java.nio.channels.SocketChannel;
+import java.text.DecimalFormat;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.FutureTask;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+import static org.onlab.junit.TestTools.delay;
+import static org.onlab.util.Tools.namedThreads;
+
+/**
+ * Auxiliary test fixture to measure speed of NIO-based channels.
+ */
+public class IOLoopClient {
+
+    private static Logger log = LoggerFactory.getLogger(IOLoopClient.class);
+
+    private final InetAddress ip;
+    private final int port;
+    private final int msgCount;
+    private final int msgLength;
+
+    private final List<CustomIOLoop> iloops = new ArrayList<>();
+    private final ExecutorService ipool;
+    private final ExecutorService wpool;
+
+    Counter messages;
+    Counter bytes;
+
+    /**
+     * Main entry point to launch the client.
+     *
+     * @param args command-line arguments
+     * @throws IOException          if unable to connect to server
+     * @throws InterruptedException if latch wait gets interrupted
+     * @throws ExecutionException   if wait gets interrupted
+     * @throws TimeoutException     if timeout occurred while waiting for completion
+     */
+    public static void main(String[] args)
+            throws IOException, InterruptedException, ExecutionException, TimeoutException {
+        InetAddress ip = InetAddress.getByName(args.length > 0 ? args[0] : "127.0.0.1");
+        int wc = args.length > 1 ? Integer.parseInt(args[1]) : 6;
+        int mc = args.length > 2 ? Integer.parseInt(args[2]) : 50 * 1000000;
+        int ml = args.length > 3 ? Integer.parseInt(args[3]) : 128;
+        int to = args.length > 4 ? Integer.parseInt(args[4]) : 30;
+
+        log.info("Setting up client with {} workers sending {} {}-byte messages to {} server... ",
+                 wc, mc, ml, ip);
+        IOLoopClient sc = new IOLoopClient(ip, wc, mc, ml, IOLoopServer.PORT);
+
+        sc.start();
+        delay(2000);
+
+        sc.await(to);
+        sc.report();
+
+        System.exit(0);
+    }
+
+    /**
+     * Creates a speed client.
+     *
+     * @param ip   ip address of server
+     * @param wc   worker count
+     * @param mc   message count to send per client
+     * @param ml   message length in bytes
+     * @param port socket port
+     * @throws IOException if unable to create IO loops
+     */
+    public IOLoopClient(InetAddress ip, int wc, int mc, int ml, int port) throws IOException {
+        this.ip = ip;
+        this.port = port;
+        this.msgCount = mc;
+        this.msgLength = ml;
+        this.wpool = Executors.newFixedThreadPool(wc, namedThreads("worker"));
+        this.ipool = Executors.newFixedThreadPool(wc, namedThreads("io-loop"));
+
+        for (int i = 0; i < wc; i++) {
+            iloops.add(new CustomIOLoop());
+        }
+    }
+
+    /**
+     * Starts the client workers.
+     *
+     * @throws IOException if unable to open connection
+     */
+    public void start() throws IOException {
+        messages = new Counter();
+        bytes = new Counter();
+
+        // First start up all the IO loops
+        for (CustomIOLoop l : iloops) {
+            ipool.execute(l);
+        }
+
+        // Wait for all of them to get going
+//        for (CustomIOLoop l : iloops)
+//            l.waitForStart(TIMEOUT);
+
+        // ... and Next open all connections; one-per-loop
+        for (CustomIOLoop l : iloops) {
+            openConnection(l);
+        }
+    }
+
+
+    /**
+     * Initiates open connection request and registers the pending socket
+     * channel with the given IO loop.
+     *
+     * @param loop loop with which the channel should be registered
+     * @throws IOException if the socket could not be open or connected
+     */
+    private void openConnection(CustomIOLoop loop) throws IOException {
+        SocketAddress sa = new InetSocketAddress(ip, port);
+        SocketChannel ch = SocketChannel.open();
+        ch.configureBlocking(false);
+        loop.connectStream(ch);
+        ch.connect(sa);
+    }
+
+
+    /**
+     * Waits for the client workers to complete.
+     *
+     * @param secs timeout in seconds
+     * @throws ExecutionException   if execution failed
+     * @throws InterruptedException if interrupt occurred while waiting
+     * @throws TimeoutException     if timeout occurred
+     */
+    public void await(int secs) throws InterruptedException,
+            ExecutionException, TimeoutException {
+        for (CustomIOLoop l : iloops) {
+            if (l.worker.task != null) {
+                l.worker.task.get(secs, TimeUnit.SECONDS);
+            }
+        }
+        messages.freeze();
+        bytes.freeze();
+    }
+
+    /**
+     * Reports on the accumulated throughput trackers.
+     */
+    public void report() {
+        DecimalFormat f = new DecimalFormat("#,##0");
+        log.info("{} messages; {} bytes; {} mps; {} Mbs",
+                 f.format(messages.total()),
+                 f.format(bytes.total()),
+                 f.format(messages.throughput()),
+                 f.format(bytes.throughput() / (1024 * 128)));
+    }
+
+
+    // Loop for transfer of fixed-length messages
+    private class CustomIOLoop extends IOLoop<TestMessage, TestMessageStream> {
+
+        Worker worker = new Worker();
+
+        public CustomIOLoop() throws IOException {
+            super(500);
+        }
+
+
+        @Override
+        protected TestMessageStream createStream(ByteChannel channel) {
+            return new TestMessageStream(msgLength, channel, this);
+        }
+
+        @Override
+        protected synchronized void removeStream(MessageStream<TestMessage> b) {
+            super.removeStream(b);
+
+            messages.add(b.messagesIn().total());
+            bytes.add(b.bytesIn().total());
+            b.messagesOut().reset();
+            b.bytesOut().reset();
+//
+            log.info("Disconnected client; inbound {} mps, {} Mbps; outbound {} mps, {} Mbps",
+                     IOLoopServer.FORMAT.format(b.messagesIn().throughput()),
+                     IOLoopServer.FORMAT.format(b.bytesIn().throughput() / (1024 * 128)),
+                     IOLoopServer.FORMAT.format(b.messagesOut().throughput()),
+                     IOLoopServer.FORMAT.format(b.bytesOut().throughput() / (1024 * 128)));
+        }
+
+        @Override
+        protected void processMessages(List<TestMessage> messages,
+                                       MessageStream<TestMessage> b) {
+            worker.release(messages.size());
+        }
+
+        @Override
+        protected void connect(SelectionKey key) {
+            super.connect(key);
+            TestMessageStream b = (TestMessageStream) key.attachment();
+            Worker w = ((CustomIOLoop) b.loop()).worker;
+            w.pump(b);
+        }
+
+    }
+
+    /**
+     * Auxiliary worker to connect and pump batched messages using blocking I/O.
+     */
+    private class Worker implements Runnable {
+
+        private static final int BATCH_SIZE = 1000;
+        private static final int PERMITS = 2 * BATCH_SIZE;
+
+        private TestMessageStream b;
+        private FutureTask<Worker> task;
+
+        // Stuff to throttle pump
+        private final Semaphore semaphore = new Semaphore(PERMITS);
+        private int msgWritten;
+
+        void pump(TestMessageStream b) {
+            this.b = b;
+            task = new FutureTask<>(this, this);
+            wpool.execute(task);
+        }
+
+        @Override
+        public void run() {
+            try {
+                log.info("Worker started...");
+
+                List<TestMessage> batch = new ArrayList<>();
+                for (int i = 0; i < BATCH_SIZE; i++) {
+                    batch.add(new TestMessage(msgLength));
+                }
+
+                while (msgWritten < msgCount) {
+                    msgWritten += writeBatch(b, batch);
+                }
+
+                // Now try to get all the permits back before sending poison pill
+                semaphore.acquireUninterruptibly(PERMITS);
+                b.close();
+
+                log.info("Worker done...");
+
+            } catch (IOException e) {
+                log.error("Worker unable to perform I/O", e);
+            }
+        }
+
+
+        private int writeBatch(TestMessageStream b, List<TestMessage> batch)
+                throws IOException {
+            int count = Math.min(BATCH_SIZE, msgCount - msgWritten);
+            acquire(count);
+            if (count == BATCH_SIZE) {
+                b.write(batch);
+            } else {
+                for (int i = 0; i < count; i++) {
+                    b.write(batch.get(i));
+                }
+            }
+            return count;
+        }
+
+
+        // Release permits based on the specified number of message credits
+        private void release(int permits) {
+            semaphore.release(permits);
+        }
+
+        // Acquire permit for a single batch
+        private void acquire(int permits) {
+            semaphore.acquireUninterruptibly(permits);
+        }
+
+    }
+
+}