diff --git a/TODO b/TODO
index 7c82d7e..2e504d4 100644
--- a/TODO
+++ b/TODO
@@ -6,6 +6,5 @@
 
 - improve searching of channel with server address specified
 
-- void transportUnresponsive() is not implemented (also in Java)
 - complete authNZ (callback on right change)
 - request event on disconnect/destroy, etc.?
diff --git a/pvtoolsSrc/pvlist.cpp b/pvtoolsSrc/pvlist.cpp
index 573ebe3..dc6a029 100644
--- a/pvtoolsSrc/pvlist.cpp
+++ b/pvtoolsSrc/pvlist.cpp
@@ -120,6 +120,10 @@ bool processSearchResponse(osiSockAddr const & responseFrom, ByteBuffer & receiv
 
     // second byte version
     int8 version = receiveBuffer.getByte();
+    if(version == 0) {
+        // 0 -> 1 included incompatible changes
+        return false;
+    }
 
     // only data for UDP
     int8 flags = receiveBuffer.getByte();
@@ -333,7 +337,7 @@ bool discoverServers(double timeOut)
     ByteBuffer sendBuffer(buffer, sizeof(buffer)/sizeof(char));
 
     sendBuffer.putByte(PVA_MAGIC);
-    sendBuffer.putByte(PVA_VERSION);
+    sendBuffer.putByte(PVA_CLIENT_PROTOCOL_REVISION);
     sendBuffer.putByte((EPICS_BYTE_ORDER == EPICS_ENDIAN_BIG) ? 0x80 : 0x00); // data + 7-bit endianess
     sendBuffer.putByte((int8_t)CMD_SEARCH);	// search
     sendBuffer.putInt(4+1+3+16+2+1+2);		// "zero" payload
diff --git a/src/pva/pv/pvaConstants.h b/src/pva/pv/pvaConstants.h
index d090141..b4423e9 100644
--- a/src/pva/pv/pvaConstants.h
+++ b/src/pva/pv/pvaConstants.h
@@ -7,6 +7,8 @@
 #ifndef PVACONSTANTS_H_
 #define PVACONSTANTS_H_
 
+#include <compilerDependencies.h>
+
 #ifdef epicsExportSharedSymbols
 #   define pvaConstantsepicsExportSharedSymbols
 #   undef epicsExportSharedSymbols
@@ -26,11 +28,14 @@ namespace pvAccess {
 /** PVA protocol magic number */
 const epics::pvData::int8 PVA_MAGIC = static_cast<epics::pvData::int8>(0xCA);
 
+const epics::pvData::int8 PVA_SERVER_PROTOCOL_REVISION = 2;
+const epics::pvData::int8 PVA_CLIENT_PROTOCOL_REVISION = 2;
+
 /** PVA protocol revision (implemented by this library). */
-const epics::pvData::int8 PVA_PROTOCOL_REVISION = 1;
+const epics::pvData::int8 PVA_PROTOCOL_REVISION EPICS_DEPRECATED = 1;
 
 /** PVA version signature used to report this implementation version in header. */
-const epics::pvData::int8 PVA_VERSION = PVA_PROTOCOL_REVISION;
+const epics::pvData::int8 PVA_VERSION EPICS_DEPRECATED = 1;
 
 /** Default PVA server port. */
 const epics::pvData::int32 PVA_SERVER_PORT = 5075;
diff --git a/src/remote/abstractResponseHandler.cpp b/src/remote/abstractResponseHandler.cpp
index 71790e4..f2d5f2d 100644
--- a/src/remote/abstractResponseHandler.cpp
+++ b/src/remote/abstractResponseHandler.cpp
@@ -4,8 +4,6 @@
  * in file LICENSE that is included with this distribution.
  */
 
-#include <sstream>
-
 #include <osiSock.h>
 
 #include <pv/byteBuffer.h>
@@ -15,9 +13,6 @@
 #include <pv/remote.h>
 #include <pv/hexDump.h>
 
-using std::ostringstream;
-using std::hex;
-
 using namespace epics::pvData;
 
 namespace epics {
@@ -44,13 +39,10 @@ void ResponseHandler::handleResponse(osiSockAddr* responseFrom,
         char ipAddrStr[48];
         ipAddrToDottedIP(&responseFrom->ia, ipAddrStr, sizeof(ipAddrStr));
 
-        ostringstream prologue;
-        prologue<<"Message [0x"<<hex<<(int)command<<", v0x"<<hex;
-        prologue<<(int)version<<"] received from "<<ipAddrStr<<" on "<<transport->getRemoteName();
-
-        hexDump(prologue.str(), _description,
-                (const int8*)payloadBuffer->getArray(),
-                payloadBuffer->getPosition(), static_cast<int>(payloadSize));
+        std::cerr<<"Message [0x"<<std::hex<<(int)command<<", v0x"<<std::hex
+                 <<int(version)<<"] received from "<<ipAddrStr<<" on "<<transport->getRemoteName()
+                 <<" : "<<_description<<"\n"
+                 <<HexDump(*payloadBuffer, payloadSize).limit(0xffff);
     }
 }
 }
diff --git a/src/remote/beaconHandler.cpp b/src/remote/beaconHandler.cpp
index 619c4de..249ebd9 100644
--- a/src/remote/beaconHandler.cpp
+++ b/src/remote/beaconHandler.cpp
@@ -37,8 +37,8 @@ void BeaconHandler::beaconNotify(osiSockAddr* /*from*/, int8 remoteTransportRevi
                                  PVFieldPtr /*data*/)
 {
     bool networkChanged = updateBeacon(remoteTransportRevision, timestamp, guid, sequentalID, changeCount);
-    if (networkChanged)
-        changedTransport();
+    // TODO: reduce search timers
+    (void)networkChanged;
 }
 
 bool BeaconHandler::updateBeacon(int8 /*remoteTransportRevision*/, TimeStamp* /*timestamp*/,
@@ -83,19 +83,6 @@ bool BeaconHandler::updateBeacon(int8 /*remoteTransportRevision*/, TimeStamp* /*
     return false;
 }
 
-void BeaconHandler::changedTransport()
-{
-    TransportRegistry::transportVector_t transports;
-    _context.lock()->getTransportRegistry()->toArray(transports, &_responseFrom);
-
-    // notify all
-    for (TransportRegistry::transportVector_t::iterator iter(transports.begin()), end(transports.end());
-         iter != end; iter++)
-    {
-        (*iter)->changedTransport();
-    }
-}
-
 }
 }
 
diff --git a/src/remote/blockingUDPTransport.cpp b/src/remote/blockingUDPTransport.cpp
index f0fca62..0293806 100644
--- a/src/remote/blockingUDPTransport.cpp
+++ b/src/remote/blockingUDPTransport.cpp
@@ -9,6 +9,8 @@
 #include <ws2tcpip.h>
 #endif
 
+#include <sstream>
+
 #include <sys/types.h>
 #include <cstdio>
 
@@ -25,6 +27,7 @@
 #include <pv/inetAddressUtil.h>
 #include <pv/logger.h>
 #include <pv/likely.h>
+#include <pv/hexDump.h>
 
 using namespace epics::pvData;
 using namespace std;
@@ -113,6 +116,16 @@ void BlockingUDPTransport::close() {
     close(true);
 }
 
+void BlockingUDPTransport::ensureData(std::size_t size) {
+    if (_receiveBuffer.getRemaining() >= size)
+        return;
+    std::ostringstream msg;
+    msg<<"no more data in UDP packet : "
+       <<_receiveBuffer.getPosition()<<":"<<_receiveBuffer.getLimit()
+       <<" for "<<size;
+    throw std::underflow_error(msg.str());
+}
+
 void BlockingUDPTransport::close(bool waitForThreadToComplete) {
     {
         Lock guard(_mutex);
@@ -194,7 +207,7 @@ void BlockingUDPTransport::flushSendQueue()
 void BlockingUDPTransport::startMessage(int8 command, size_t /*ensureCapacity*/, int32 payloadSize) {
     _lastMessageStartPosition = _sendBuffer.getPosition();
     _sendBuffer.putByte(PVA_MAGIC);
-    _sendBuffer.putByte(PVA_VERSION);
+    _sendBuffer.putByte((_clientServerWithEndianFlag&0x40) ? PVA_SERVER_PROTOCOL_REVISION : PVA_CLIENT_PROTOCOL_REVISION);
     _sendBuffer.putByte(_clientServerWithEndianFlag);
     _sendBuffer.putByte(command); // command
     _sendBuffer.putInt(payloadSize);
@@ -255,13 +268,18 @@ void BlockingUDPTransport::run() {
                     try {
                         processBuffer(thisTransport, fromAddress, &_receiveBuffer);
                     } catch(std::exception& e) {
-                        LOG(logLevelError,
-                            "an exception caught while in UDP receiveThread at %s:%d: %s",
-                            __FILE__, __LINE__, e.what());
-                    } catch (...) {
-                        LOG(logLevelError,
-                            "unknown exception caught while in UDP receiveThread at %s:%d.",
-                            __FILE__, __LINE__);
+                        if(IS_LOGGABLE(logLevelError)) {
+                            char strBuffer[64];
+                            sockAddrToDottedIP(&fromAddress.sa, strBuffer, sizeof(strBuffer));
+                            size_t epos = _receiveBuffer.getPosition();
+
+                            // of course _receiveBuffer _may_ have been modified during processing...
+                            _receiveBuffer.setPosition(RECEIVE_BUFFER_PRE_RESERVE);
+                            _receiveBuffer.setLimit(RECEIVE_BUFFER_PRE_RESERVE+bytesRead);
+
+                            std::cerr<<"Error on UDP RX "<<strBuffer<<" -> "<<_remoteName<<" at "<<epos<<" : "<<e.what()<<"\n"
+                                      <<HexDump(_receiveBuffer).limit(256u);
+                        }
                     }
                 }
             } else {
@@ -323,6 +341,10 @@ bool BlockingUDPTransport::processBuffer(Transport::shared_pointer const & trans
 
         // second byte version
         int8 version = receiveBuffer->getByte();
+        if(version==0) {
+            // 0 -> 1 included incompatible changes
+            return false;
+        }
 
         int8 flags = receiveBuffer->getByte();
         if (flags & 0x80)
@@ -558,6 +580,8 @@ void initializeUDPTransports(bool serverFlag,
 {
     BlockingUDPConnector connector(serverFlag);
 
+    const int8_t protoVer = serverFlag ? PVA_SERVER_PROTOCOL_REVISION : PVA_CLIENT_PROTOCOL_REVISION;
+
     //
     // Create UDP transport for sending (to all network interfaces)
     //
@@ -568,7 +592,7 @@ void initializeUDPTransports(bool serverFlag,
     anyAddress.ia.sin_port = htons(0);
     anyAddress.ia.sin_addr.s_addr = htonl(INADDR_ANY);
 
-    sendTransport = connector.connect(responseHandler, anyAddress, PVA_PROTOCOL_REVISION);
+    sendTransport = connector.connect(responseHandler, anyAddress, protoVer);
     if (!sendTransport)
     {
         THROW_BASE_EXCEPTION("Failed to initialize UDP transport.");
@@ -708,7 +732,7 @@ void initializeUDPTransports(bool serverFlag,
             listenLocalAddress.ia.sin_addr.s_addr = node.addr.ia.sin_addr.s_addr;
 
             BlockingUDPTransport::shared_pointer transport = connector.connect(
-                        responseHandler, listenLocalAddress, PVA_PROTOCOL_REVISION);
+                        responseHandler, listenLocalAddress, protoVer);
             if (!transport)
                 continue;
             listenLocalAddress = transport->getRemoteAddress();
@@ -742,7 +766,7 @@ void initializeUDPTransports(bool serverFlag,
                 bcastAddress.ia.sin_port = htons(listenPort);
                 bcastAddress.ia.sin_addr.s_addr = node.bcast.ia.sin_addr.s_addr;
 
-                transport2 = connector.connect(responseHandler, bcastAddress, PVA_PROTOCOL_REVISION);
+                transport2 = connector.connect(responseHandler, bcastAddress, protoVer);
                 if (transport2)
                 {
                     /* The other wrinkle is that nothing should be sent from this second
@@ -802,7 +826,7 @@ void initializeUDPTransports(bool serverFlag,
 #else
                                       anyAddress,
 #endif
-                                      PVA_PROTOCOL_REVISION);
+                                      protoVer);
         if (!localMulticastTransport)
             throw std::runtime_error("Failed to bind UDP socket.");
 
diff --git a/src/remote/channelSearchManager.cpp b/src/remote/channelSearchManager.cpp
index a11cd4e..ec97ae8 100644
--- a/src/remote/channelSearchManager.cpp
+++ b/src/remote/channelSearchManager.cpp
@@ -206,7 +206,7 @@ void ChannelSearchManager::initializeSendBuffer()
     // new buffer
     m_sendBuffer.clear();
     m_sendBuffer.putByte(PVA_MAGIC);
-    m_sendBuffer.putByte(PVA_VERSION);
+    m_sendBuffer.putByte(PVA_CLIENT_PROTOCOL_REVISION);
     m_sendBuffer.putByte((EPICS_BYTE_ORDER == EPICS_ENDIAN_BIG) ? 0x80 : 0x00); // data + 7-bit endianess
     m_sendBuffer.putByte(CMD_SEARCH);
     m_sendBuffer.putInt(4+1+3+16+2+1);		// "zero" payload
diff --git a/src/remote/codec.cpp b/src/remote/codec.cpp
index 416f21f..cfc0809 100644
--- a/src/remote/codec.cpp
+++ b/src/remote/codec.cpp
@@ -16,6 +16,7 @@
 #include <epicsTime.h>
 #include <epicsThread.h>
 #include <epicsVersion.h>
+#include <errlog.h>
 
 #include <pv/byteBuffer.h>
 #include <pv/pvType.h>
@@ -94,7 +95,7 @@ AbstractCodec::AbstractCodec(
     _remoteTransportSocketReceiveBufferSize(MAX_TCP_RECV), _totalBytesSent(0),
     _senderThread(0),
     _writeMode(PROCESS_SEND_QUEUE),
-    _writeOpReady(false),_lowLatency(false),
+    _writeOpReady(false),
     _socketBuffer(bufSizeSelect(receiveBufferSize)),
     _sendBuffer(bufSizeSelect(sendBufferSize)),
     //PRIVATE
@@ -147,7 +148,12 @@ void AbstractCodec::processHeader() {
     int8_t magicCode = _socketBuffer.getByte();
 
     // version
-    _version = _socketBuffer.getByte();
+    int8_t ver = _socketBuffer.getByte();
+    if(_version!=ver) {
+        // enable timeout if both ends support
+        _version = ver;
+        setRxTimeout(getRevision()>1);
+    }
 
     // flags
     _flags = _socketBuffer.getByte();
@@ -159,12 +165,12 @@ void AbstractCodec::processHeader() {
     _payloadSize = _socketBuffer.getInt();
 
     // check magic code
-    if (magicCode != PVA_MAGIC)
+    if (magicCode != PVA_MAGIC || _version==0)
     {
         LOG(logLevelError,
-            "Invalid header received from the client at %s:%d: %s.,"
-            " disconnecting...",
-            __FILE__, __LINE__, inetAddressToString(*getLastReadBufferSocketAddress()).c_str());
+            "Invalid header received from the client : %s %02x%02x%02x%02x disconnecting...",
+            inetAddressToString(*getLastReadBufferSocketAddress()).c_str(),
+            unsigned(magicCode), unsigned(_version), unsigned(_flags), unsigned(_command));
         invalidDataStreamHandler();
         throw invalid_data_stream_exception("invalid header received");
     }
@@ -185,12 +191,6 @@ void AbstractCodec::processReadNormal()  {
                 return;
             }
 
-            /*
-            hexDump("Header", (const int8*)_socketBuffer.getArray(),
-                    _socketBuffer.getPosition(), PVA_MESSAGE_HEADER_SIZE);
-
-            */
-
             // read header fields
             processHeader();
             bool isControl = ((_flags & 0x01) == 0x01);
@@ -597,7 +597,7 @@ void AbstractCodec::startMessage(
         PVA_MESSAGE_HEADER_SIZE + ensureCapacity + _nextMessagePayloadOffset);
     _lastMessageStartPosition = _sendBuffer.getPosition();
     _sendBuffer.putByte(PVA_MAGIC);
-    _sendBuffer.putByte(PVA_VERSION);
+    _sendBuffer.putByte(_clientServerFlag ? PVA_SERVER_PROTOCOL_REVISION : PVA_CLIENT_PROTOCOL_REVISION);
     _sendBuffer.putByte(
         (_lastSegmentedMessageType | _byteOrderFlag | _clientServerFlag));	// data message
     _sendBuffer.putByte(command);	// command
@@ -618,7 +618,7 @@ void AbstractCodec::putControlMessage(
         std::numeric_limits<size_t>::max();		// TODO revise this
     ensureBuffer(PVA_MESSAGE_HEADER_SIZE);
     _sendBuffer.putByte(PVA_MAGIC);
-    _sendBuffer.putByte(PVA_VERSION);
+    _sendBuffer.putByte(_clientServerFlag ? PVA_SERVER_PROTOCOL_REVISION : PVA_CLIENT_PROTOCOL_REVISION);
     _sendBuffer.putByte((0x01 | _byteOrderFlag | _clientServerFlag));	// control message
     _sendBuffer.putByte(command);	// command
     _sendBuffer.putInt(data);		// data
@@ -797,14 +797,6 @@ void AbstractCodec::send(ByteBuffer *buffer)
         //int p = buffer.position();
         int bytesSent = write(buffer);
 
-        /*
-        if (IS_LOGGABLE(logLevelTrace)) {
-          hexDump(std::string("AbstractCodec::send WRITE"),
-            (const int8 *)buffer->getArray(),
-            buffer->getPosition(), buffer->getRemaining());
-        }
-        */
-
         if (bytesSent < 0)
         {
             // connection lost
@@ -934,10 +926,7 @@ void AbstractCodec::enqueueSendRequest(
         processSender(sender);
         if (_sendBuffer.getPosition() > 0)
         {
-            if (_lowLatency)
-                flush(true);
-            else
-                scheduleSend();
+            scheduleSend();
         }
     }
     else
@@ -1132,6 +1121,10 @@ void BlockingTCPTransportCodec::receiveThread()
      */
     Transport::shared_pointer ptr(this->shared_from_this());
 
+    // initially enable timeout for all clients to weed out
+    // impersonators (security scanners?)
+    setRxTimeout(true);
+
     while (this->isOpen())
     {
         try {
@@ -1183,6 +1176,27 @@ void BlockingTCPTransportCodec::sendThread()
     _sendQueue.clear();
 }
 
+void BlockingTCPTransportCodec::setRxTimeout(bool ena)
+{
+    double timeout = !ena ? 0.0 : std::max(0.0, _context->getConfiguration()->getPropertyAsDouble("EPICS_PVA_CONN_TMO", 30.0));
+#ifdef _WIN32
+    DWORD timo = DWORD(timeout*1000); // in milliseconds
+#else
+    timeval timo;
+    timo.tv_sec = unsigned(timeout);
+    timo.tv_usec = (timeout-timo.tv_sec)*1e6;
+#endif
+
+    int ret = setsockopt(_channel, SOL_SOCKET, SO_RCVTIMEO, (const char*)&timo, sizeof(timo));
+    if(ret==-1) {
+        int err = SOCKERRNO;
+        static int lasterr;
+        if(err!=lasterr) {
+            errlogPrintf("%s: Unable to set RX timeout: %d\n", _socketName.c_str(), err);
+            lasterr = err;
+        }
+    }
+}
 
 void BlockingTCPTransportCodec::sendBufferFull(int tries) {
     // TODO constants
@@ -1302,28 +1316,35 @@ int BlockingTCPTransportCodec::read(epics::pvData::ByteBuffer* dst) {
 
         // NOTE: do not log here, you might override SOCKERRNO relevant to recv() operation above
 
-        /*
-        if (IS_LOGGABLE(logLevelTrace)) {
-          hexDump(std::string("READ"),
-            (const int8 *)(dst->getArray()+pos), bytesRead);
-        }
-        */
-
-        if(unlikely(bytesRead<=0)) {
-
-            if (bytesRead<0)
-            {
-                int socketError = SOCKERRNO;
-
-                // TODO SOCK_ENOBUFS, for read?
-                // interrupted or timeout
-                if (socketError == SOCK_EINTR ||
-                        socketError == EAGAIN ||
-                        socketError == SOCK_EWOULDBLOCK)
-                    continue;
-            }
-
+        if(unlikely(bytesRead==0)) {
             return -1;    // 0 means connection loss for blocking transport, notify codec by returning -1
+
+        } else if(unlikely(bytesRead<0)) {
+            int err = SOCKERRNO;
+
+            if(err==SOCK_EINTR) {
+                // interrupted by signal.  Retry
+                continue;
+
+            } else if(err==SOCK_EWOULDBLOCK || err==EAGAIN || err==SOCK_EINPROGRESS
+                      || err==SOCK_ETIMEDOUT
+                      || err==SOCK_ECONNABORTED || err==SOCK_ECONNRESET
+                      ) {
+                // different ways of saying timeout.
+                // Linux: EAGAIN or EWOULDBLOCK, or EINPROGRESS
+                // WIN32: WSAETIMEDOUT
+                // others that RSRV checks for, but may not need to, ECONNABORTED, ECONNRESET
+
+                // Note: with windows, after ETIMEOUT leaves the socket in an undefined state.
+                //       so it must be closed.  (cf. SO_RCVTIMEO)
+
+                return -1;
+
+            } else {
+                // some other (fatal) error
+                errlogPrintf("%s : Connection closed with RX socket error %d\n", _socketName.c_str(), err);
+                return -1;
+            }
         }
 
         dst->setPosition(dst->getPosition() + bytesRead);
@@ -1493,7 +1514,7 @@ void BlockingServerTCPTransportCodec::send(ByteBuffer* buffer,
 
         ensureBuffer(PVA_MESSAGE_HEADER_SIZE);
         buffer->putByte(PVA_MAGIC);
-        buffer->putByte(PVA_VERSION);
+        buffer->putByte(PVA_SERVER_PROTOCOL_REVISION);
         buffer->putByte(
             0x01 | 0x40 | ((EPICS_BYTE_ORDER == EPICS_ENDIAN_BIG)
                            ? 0x80 : 0x00));		// control + server + endian
@@ -1675,24 +1696,25 @@ BlockingClientTCPTransportCodec::BlockingClientTCPTransportCodec(
     int16_t priority ) :
     BlockingTCPTransportCodec(false, context, channel, responseHandler,
                               sendBufferSize, receiveBufferSize, priority),
-    _connectionTimeout(heartbeatInterval*1000),
-    _unresponsiveTransport(false),
-    _verifyOrEcho(true)
+    _connectionTimeout(heartbeatInterval),
+    _verifyOrEcho(true),
+    sendQueued(true) // don't start sending echo until after auth complete
 {
     // initialize owners list, send queue
     acquire(client);
 
     // use immediate for clients
     //setFlushStrategy(DELAYED);
-
-    // setup connection timeout timer (watchdog) - moved to start() method
-    epicsTimeGetCurrent(&_aliveTimestamp);
 }
 
 void BlockingClientTCPTransportCodec::start()
 {
     TimerCallbackPtr tcb = std::tr1::dynamic_pointer_cast<TimerCallback>(shared_from_this());
-    _context->getTimer()->schedulePeriodic(tcb, _connectionTimeout, _connectionTimeout);
+    // add some randomness to our timer phase
+    double R = float(rand())/RAND_MAX; // [0, 1]
+    // shape a bit
+    R = R*0.5 + 0.5; // [0.5, 1.0]
+    _context->getTimer()->schedulePeriodic(tcb, _connectionTimeout/2.0*R, _connectionTimeout/2.0);
     BlockingTCPTransportCodec::start();
 }
 
@@ -1707,46 +1729,22 @@ BlockingClientTCPTransportCodec::~BlockingClientTCPTransportCodec() {
 
 
 
-void BlockingClientTCPTransportCodec::callback() {
-    epicsTimeStamp currentTime;
-    epicsTimeGetCurrent(&currentTime);
-
-    _mutex.lock();
-    // no exception expected here
-    double diff = epicsTimeDiffInSeconds(&currentTime, &_aliveTimestamp);
-    _mutex.unlock();
-
-    if(diff>((3*_connectionTimeout)/2)) {
-        unresponsiveTransport();
-    }
-    // use some k (3/4) to handle "jitter"
-    else if(diff>=((3*_connectionTimeout)/4)) {
-        // send echo
-        TransportSender::shared_pointer transportSender = std::tr1::dynamic_pointer_cast<TransportSender>(shared_from_this());
-        enqueueSendRequest(transportSender);
+void BlockingClientTCPTransportCodec::callback()
+{
+    {
+        Guard G(_mutex);
+        if(sendQueued) return;
+        sendQueued = true;
     }
+    // send echo
+    TransportSender::shared_pointer transportSender = std::tr1::dynamic_pointer_cast<TransportSender>(shared_from_this());
+    enqueueSendRequest(transportSender);
 }
 
 #define EXCEPTION_GUARD(code) try { code; } \
         catch (std::exception &e) { LOG(logLevelError, "Unhandled exception caught from code at %s:%d: %s", __FILE__, __LINE__, e.what()); } \
                 catch (...) { LOG(logLevelError, "Unhandled exception caught from code at %s:%d.", __FILE__, __LINE__); }
 
-void BlockingClientTCPTransportCodec::unresponsiveTransport() {
-    Lock lock(_mutex);
-    if(!_unresponsiveTransport) {
-        _unresponsiveTransport = true;
-
-        TransportClientMap_t::iterator it = _owners.begin();
-        for(; it!=_owners.end(); it++) {
-            ClientChannelImpl::shared_pointer client = it->second.lock();
-            if (client)
-            {
-                EXCEPTION_GUARD(client->transportUnresponsive());
-            }
-        }
-    }
-}
-
 bool BlockingClientTCPTransportCodec::acquire(ClientChannelImpl::shared_pointer const & client) {
     Lock lock(_mutex);
     if(isClosed()) return false;
@@ -1820,48 +1818,18 @@ void BlockingClientTCPTransportCodec::release(pvAccessID clientID) {
     }
 }
 
-void BlockingClientTCPTransportCodec::aliveNotification() {
-    Lock guard(_mutex);
-    epicsTimeGetCurrent(&_aliveTimestamp);
-    if(_unresponsiveTransport) responsiveTransport();
-}
-
-void BlockingClientTCPTransportCodec::responsiveTransport() {
-    Lock lock(_mutex);
-    if(_unresponsiveTransport) {
-        _unresponsiveTransport = false;
-
-        Transport::shared_pointer thisSharedPtr = shared_from_this();
-        TransportClientMap_t::iterator it = _owners.begin();
-        for(; it!=_owners.end(); it++) {
-            ClientChannelImpl::shared_pointer client = it->second.lock();
-            if (client)
-            {
-                EXCEPTION_GUARD(client->transportResponsive(thisSharedPtr));
-            }
-        }
-    }
-}
-
-void BlockingClientTCPTransportCodec::changedTransport() {
-    _outgoingIR.reset();
-
-    Lock lock(_mutex);
-    TransportClientMap_t::iterator it = _owners.begin();
-    for(; it!=_owners.end(); it++) {
-        ClientChannelImpl::shared_pointer client = it->second.lock();
-        if (client)
-        {
-            EXCEPTION_GUARD(client->transportChanged());
-        }
-    }
-}
-
 void BlockingClientTCPTransportCodec::send(ByteBuffer* buffer,
-        TransportSendControl* control) {
-    if(_verifyOrEcho) {
+                                           TransportSendControl* control)
+{
+    bool voe;
+    {
+        Guard G(_mutex);
+        sendQueued = false;
+        voe = _verifyOrEcho;
         _verifyOrEcho = false;
+    }
 
+    if(voe) {
         /*
          * send verification response message
          */
diff --git a/src/remote/pv/beaconHandler.h b/src/remote/pv/beaconHandler.h
index b6c2bb8..dbaeccd 100644
--- a/src/remote/pv/beaconHandler.h
+++ b/src/remote/pv/beaconHandler.h
@@ -101,10 +101,6 @@ private:
                       ServerGUID const &guid,
                       epics::pvData::int16 sequentalID,
                       epics::pvData::int16 changeCount);
-    /**
-     * Changed transport (server restarted) notify.
-     */
-    void changedTransport();
 };
 
 }
diff --git a/src/remote/pv/blockingUDP.h b/src/remote/pv/blockingUDP.h
index f1c560f..5312c61 100644
--- a/src/remote/pv/blockingUDP.h
+++ b/src/remote/pv/blockingUDP.h
@@ -97,14 +97,6 @@ public:
         // noop for UDP (limited by 64k; MAX_UDP_SEND for PVA)
     }
 
-    virtual void aliveNotification() OVERRIDE FINAL {
-        // noop
-    }
-
-    virtual void changedTransport() OVERRIDE FINAL {
-        // noop
-    }
-
     virtual bool verify(epics::pvData::int32 /*timeoutMs*/) OVERRIDE FINAL {
         // noop
         return true;
@@ -135,10 +127,7 @@ public:
 
     virtual void close() OVERRIDE FINAL;
 
-    virtual void ensureData(std::size_t size) OVERRIDE FINAL {
-        if (_receiveBuffer.getRemaining() < size)
-            throw std::underflow_error("no more data in UDP packet");
-    }
+    virtual void ensureData(std::size_t size) OVERRIDE FINAL;
 
     virtual void alignData(std::size_t alignment) OVERRIDE FINAL {
         _receiveBuffer.align(alignment);
diff --git a/src/remote/pv/codec.h b/src/remote/pv/codec.h
index c8138dc..43e941d 100644
--- a/src/remote/pv/codec.h
+++ b/src/remote/pv/codec.h
@@ -240,12 +240,19 @@ public:
         return _sendQueue.empty();
     }
 
+    epics::pvData::int8 getRevision() const {
+        epicsGuard<epicsMutex> G(_mutex);
+        int8_t myver = _clientServerFlag ? PVA_SERVER_PROTOCOL_REVISION : PVA_CLIENT_PROTOCOL_REVISION;
+        return myver < _version ? myver : _version;
+    }
+
 protected:
 
     virtual void sendBufferFull(int tries) = 0;
     void send(epics::pvData::ByteBuffer *buffer);
     void flushSendBuffer();
 
+    virtual void setRxTimeout(bool ena) {}
 
     ReadMode _readMode;
     int8_t _version;
@@ -259,7 +266,6 @@ protected:
     epicsThreadId _senderThread;
     WriteMode _writeMode;
     bool _writeOpReady;
-    bool _lowLatency;
 
     epics::pvData::ByteBuffer _socketBuffer;
     epics::pvData::ByteBuffer _sendBuffer;
@@ -289,7 +295,9 @@ private:
     std::size_t _nextMessagePayloadOffset;
 
     epics::pvData::int8 _byteOrderFlag;
-    epics::pvData::int8 _clientServerFlag;
+protected:
+    const epics::pvData::int8 _clientServerFlag;
+private:
     const size_t _socketSendBufferSize;
 
 public:
@@ -327,7 +335,7 @@ public:
     virtual void waitJoin() OVERRIDE FINAL;
     virtual bool terminated() OVERRIDE FINAL;
     virtual bool isOpen() OVERRIDE FINAL;
-    void start();
+    virtual void start();
 
     virtual int read(epics::pvData::ByteBuffer* dst) OVERRIDE FINAL;
     virtual int write(epics::pvData::ByteBuffer* src) OVERRIDE FINAL;
@@ -363,12 +371,6 @@ public:
         return _socketName;
     }
 
-    epics::pvData::int8 getRevision() const {
-        epicsGuard<epicsMutex> G(_mutex);
-        return PVA_PROTOCOL_REVISION < _version
-                ? PVA_PROTOCOL_REVISION : _version;
-    }
-
 
     virtual std::size_t getReceiveBufferSize() const OVERRIDE FINAL {
         return _socketBuffer.getSize();
@@ -435,6 +437,8 @@ private:
     void sendThread();
 
 protected:
+    virtual void setRxTimeout(bool ena) OVERRIDE FINAL;
+
     virtual void sendBufferFull(int tries) OVERRIDE FINAL;
 
     /**
@@ -515,8 +519,6 @@ public:
 
     virtual void release(pvAccessID /*clientId*/) OVERRIDE FINAL {}
 
-    virtual void changedTransport() OVERRIDE {}
-
     pvAccessID preallocateChannelSID();
 
     void depreallocateChannelSID(pvAccessID /*sid*/) {}
@@ -554,10 +556,6 @@ public:
         BlockingTCPTransportCodec::verified(status);
     }
 
-    virtual void aliveNotification() OVERRIDE FINAL {
-        // noop on server-side
-    }
-
     void authNZInitialize(const std::string& securityPluginName,
                           const epics::pvData::PVStructure::shared_pointer& data);
 
@@ -642,7 +640,7 @@ public:
 
 public:
 
-    void start();
+    virtual void start() OVERRIDE FINAL;
 
     virtual ~BlockingClientTCPTransportCodec() OVERRIDE FINAL;
 
@@ -656,10 +654,6 @@ public:
 
     virtual void release(pvAccessID clientId) OVERRIDE FINAL;
 
-    virtual void changedTransport() OVERRIDE FINAL;
-
-    virtual void aliveNotification() OVERRIDE FINAL;
-
     virtual void send(epics::pvData::ByteBuffer* buffer,
                       TransportSendControl* control) OVERRIDE FINAL;
 
@@ -685,34 +679,17 @@ private:
     /**
      * Connection timeout (no-traffic) flag.
      */
-    double _connectionTimeout;
-
-    /**
-     * Unresponsive transport flag.
-     */
-    bool _unresponsiveTransport;
-
-    /**
-     * Timestamp of last "live" event on this transport.
-     */
-    epicsTimeStamp _aliveTimestamp;
+    const double _connectionTimeout;
 
     bool _verifyOrEcho;
 
-    /**
-     * Unresponsive transport notify.
-     */
-    void unresponsiveTransport();
+    // are we queued to send verify or echo?
+    bool sendQueued;
 
     /**
      * Notifies clients about disconnect.
      */
     void closedNotifyClients();
-
-    /**
-     * Responsive transport notify.
-     */
-    void responsiveTransport();
 };
 
 }
diff --git a/src/remote/pv/remote.h b/src/remote/pv/remote.h
index b096008..6521677 100644
--- a/src/remote/pv/remote.h
+++ b/src/remote/pv/remote.h
@@ -222,11 +222,6 @@ public:
     // TODO enum
     virtual void setByteOrder(int byteOrder) = 0;
 
-    /**
-     * Notification that transport has changed.
-     */
-    virtual void changedTransport() = 0;
-
     /**
      * Enqueue send request.
      * @param sender
@@ -250,11 +245,6 @@ public:
      */
     virtual bool verify(epics::pvData::int32 timeoutMs) = 0;
 
-    /**
-     * Notification transport that is still alive.
-     */
-    virtual void aliveNotification() = 0;
-
     /**
      * Close transport.
      */
diff --git a/src/remote/security.cpp b/src/remote/security.cpp
index c19c8e2..5838028 100644
--- a/src/remote/security.cpp
+++ b/src/remote/security.cpp
@@ -95,9 +95,15 @@ struct CAPlugin : public pva::AuthenticationPlugin
     {
         std::tr1::shared_ptr<SimpleSession> sess(new SimpleSession(user)); // no init data
         if(server) {
-            peer->identified = true;
-            peer->account = data->getSubFieldT<pvd::PVString>("user")->get();
-            peer->aux = pvd::getPVDataCreate()->createPVStructure(data); // clone to ensure it won't be modified
+            pvd::PVString::shared_pointer user;
+            if(data)
+                user = data->getSubField<pvd::PVString>("user");
+
+            if(user) {
+                peer->account = user->get();
+                peer->identified = !peer->account.empty();
+                peer->aux = pvd::getPVDataCreate()->createPVStructure(data); // clone to ensure it won't be modified
+            }
             control->authenticationCompleted(pvd::Status::Ok, peer);
         }
         return sess;
diff --git a/src/remoteClient/clientContextImpl.cpp b/src/remoteClient/clientContextImpl.cpp
index bea6744..45d0b70 100644
--- a/src/remoteClient/clientContextImpl.cpp
+++ b/src/remoteClient/clientContextImpl.cpp
@@ -2998,10 +2998,10 @@ public:
     {
         if (command < 0 || command >= (int8)m_handlerTable.size())
         {
-            // TODO remove debug output
-            char buf[100];
-            sprintf(buf, "Invalid (or unsupported) command %d, its payload", command);
-            hexDump(buf, (const int8*)(payloadBuffer->getArray()), payloadBuffer->getPosition(), payloadSize);
+            if(IS_LOGGABLE(logLevelError)) {
+                std::cerr<<"Invalid (or unsupported) command: "<<std::hex<<(int)(0xFF&command)<<"\n"
+                         <<HexDump(*payloadBuffer, payloadSize).limit(256u);
+            }
             return;
         }
         // delegate
@@ -3597,7 +3597,7 @@ public:
             // NOTE: calls channelConnectFailed() on failure
             static ServerGUID guid = { { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 } };
             // m_addresses[ix] is modified by the following
-            searchResponse(guid, PVA_PROTOCOL_REVISION, &m_addresses[ix]);
+            searchResponse(guid, PVA_CLIENT_PROTOCOL_REVISION, &m_addresses[ix]);
         }
 
         virtual void timerStopped() OVERRIDE FINAL {
@@ -3675,13 +3675,6 @@ public:
             reportChannelStateChange();
         }
 
-        virtual void transportChanged() OVERRIDE FINAL {
-//                    initiateSearch();
-            // TODO
-            // this will be called immediately after reconnect... bad...
-
-        }
-
         virtual Transport::shared_pointer checkAndGetTransport() OVERRIDE FINAL
         {
             Lock guard(m_channelMutex);
@@ -3711,35 +3704,6 @@ public:
             return m_transport;
         }
 
-        virtual void transportResponsive(Transport::shared_pointer const & /*transport*/) OVERRIDE FINAL {
-            Lock guard(m_channelMutex);
-            if (m_connectionState == DISCONNECTED)
-            {
-                updateSubscriptions();
-
-                // reconnect using existing IDs, data
-                connectionCompleted(m_serverChannelID/*, accessRights*/);
-            }
-        }
-
-        virtual void transportUnresponsive() OVERRIDE FINAL {
-            /*
-            {
-                Lock guard(m_channelMutex);
-                if (m_connectionState == CONNECTED)
-                {
-            		// TODO 2 types of disconnected state - distinguish them otherwise disconnect will handle connection loss right
-                    setConnectionState(DISCONNECTED);
-
-                    // ... PVA notifies also w/ no access rights callback, although access right are not changed
-                }
-            }
-
-            // should be called without any lock hold
-            reportChannelStateChange();
-            */
-        }
-
         /**
          * Set connection state and if changed, notifies listeners.
          * @param newState    state to set.
diff --git a/src/remoteClient/pv/clientContextImpl.h b/src/remoteClient/pv/clientContextImpl.h
index a003d65..7c04f69 100644
--- a/src/remoteClient/pv/clientContextImpl.h
+++ b/src/remoteClient/pv/clientContextImpl.h
@@ -53,10 +53,7 @@ public:
     virtual Transport::shared_pointer checkAndGetTransport() = 0;
     virtual Transport::shared_pointer checkDestroyedAndGetTransport() = 0;
     virtual Transport::shared_pointer getTransport() = 0;
-    virtual void transportUnresponsive() =0;
-    virtual void transportChanged() =0;
     virtual void transportClosed() =0;
-    virtual void transportResponsive(Transport::shared_pointer const & /*transport*/) =0;
 
     static epics::pvData::Status channelDestroyed;
     static epics::pvData::Status channelDisconnected;
diff --git a/src/server/pv/responseHandlers.h b/src/server/pv/responseHandlers.h
index 3299cac..f090850 100644
--- a/src/server/pv/responseHandlers.h
+++ b/src/server/pv/responseHandlers.h
@@ -93,20 +93,23 @@ public:
 
 class EchoTransportSender : public TransportSender {
 public:
-    EchoTransportSender(osiSockAddr* echoFrom) {
+    EchoTransportSender(osiSockAddr* echoFrom, size_t payloadSize, epics::pvData::ByteBuffer& payloadBuffer) {
         memcpy(&_echoFrom, echoFrom, sizeof(osiSockAddr));
+        toEcho.resize(payloadSize);
+        payloadBuffer.getArray(&toEcho[0], payloadSize);
     }
 
     virtual ~EchoTransportSender() {}
 
-    virtual void send(epics::pvData::ByteBuffer* /*buffer*/, TransportSendControl* control) OVERRIDE FINAL {
-        control->startMessage(CMD_ECHO, 0);
+    virtual void send(epics::pvData::ByteBuffer* buffer, TransportSendControl* control) OVERRIDE FINAL {
+        control->startMessage(CMD_ECHO, toEcho.size(), toEcho.size());
         control->setRecipient(_echoFrom);
-        // TODO content
+        buffer->putArray<char>(&toEcho[0], toEcho.size());
     }
 
 private:
     osiSockAddr _echoFrom;
+    std::vector<char> toEcho;
 };
 
 /****************************************************************************************/
diff --git a/src/server/responseHandlers.cpp b/src/server/responseHandlers.cpp
index 11853cb..e115504 100644
--- a/src/server/responseHandlers.cpp
+++ b/src/server/responseHandlers.cpp
@@ -155,16 +155,13 @@ void ServerResponseHandler::handleResponse(osiSockAddr* responseFrom,
 {
     if(command<0||command>=(int8)m_handlerTable.size())
     {
-        LOG(logLevelDebug,
+        LOG(logLevelError,
             "Invalid (or unsupported) command: %x.", (0xFF&command));
 
-        // TODO remove debug output
-        std::ostringstream name;
-        name<<"Invalid PVA header "<<hex<<(int)(0xFF&command);
-        name<<", its payload buffer";
-
-        hexDump(name.str(), (const int8*)payloadBuffer->getArray(),
-                payloadBuffer->getPosition(), payloadSize);
+        if(IS_LOGGABLE(logLevelError)) {
+            std::cerr<<"Invalid (or unsupported) command: "<<std::hex<<(int)(0xFF&command)<<"\n"
+                     <<HexDump(*payloadBuffer, payloadSize).limit(256u);
+        }
         return;
     }
 
@@ -231,7 +228,7 @@ void ServerEchoHandler::handleResponse(osiSockAddr* responseFrom,
             transport, version, command, payloadSize, payloadBuffer);
 
     // send back
-    TransportSender::shared_pointer echoReply(new EchoTransportSender(responseFrom));
+    TransportSender::shared_pointer echoReply(new EchoTransportSender(responseFrom, payloadSize, *payloadBuffer));
     transport->enqueueSendRequest(echoReply);
 }
 
diff --git a/src/utils/hexDump.cpp b/src/utils/hexDump.cpp
index b47651d..5f701b9 100644
--- a/src/utils/hexDump.cpp
+++ b/src/utils/hexDump.cpp
@@ -7,102 +7,92 @@
 #include <iostream>
 #include <sstream>
 #include <string>
+#include <iomanip>
+#include <algorithm>
+
+#include <pv/byteBuffer.h>
 
 #define epicsExportSharedSymbols
 #include <pv/hexDump.h>
 
-using namespace epics::pvData;
-using std::string;
-using std::stringstream;
-using std::endl;
-using std::cout;
-
 namespace epics {
 namespace pvAccess {
 
-/// Byte to hexchar mapping.
-static const char lookup[] = {
-    '0', '1', '2', '3', '4', '5', '6', '7',
-    '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
-};
+HexDump::HexDump(const char* buf, size_t len)
+    :buf(buf)
+    ,buflen(len)
+    ,_limit(1024u)
+    ,_groupBy(4u)
+    ,_perLine(16u)
+{}
 
-/// Get hex representation of byte.
-string toHex(int8 b) {
-    string sb;
-
-    int upper = (b>>4)&0x0F;
-    sb += lookup[upper];
-
-    int lower = b&0x0F;
-    sb += lookup[lower];
-
-    sb += ' ';
-
-    return sb;
+HexDump::HexDump(const pvData::ByteBuffer& bb,
+                 size_t size, size_t offset)
+    :buf(bb.getBuffer() + bb.getPosition())
+    ,buflen(bb.getRemaining())
+    ,_limit((size_t)-1)
+    ,_groupBy(4u)
+    ,_perLine(16u)
+{
+    if(offset > buflen)
+        offset = buflen;
+    buf    += offset;
+    buflen -= offset;
+    if(buflen > size)
+        buflen = size;
 }
 
-/// Get ASCII representation of byte, dot if non-readable.
-char toAscii(int8 b) {
-    if(b>(int8)31&&b<(int8)127)
-        return (char)b;
-    else
-        return '.';
+HexDump::~HexDump() {}
+
+static
+size_t ilog2(size_t val)
+{
+    size_t ret = 0;
+    while(val >>= 1)
+        ret++;
+    return ret;
 }
 
-void hexDump(std::string const & name, const int8 *bs, int len) {
-    hexDump(name, bs, 0, len);
+static
+size_t bits2bytes(size_t val)
+{
+    // round up to next multiple of 8
+    val -= 1u;
+    val |= 7u;
+    val += 1u;
+    // bits -> bytes
+    val /= 8u;
+    return val;
 }
 
-void hexDump(std::string const & name, const int8 *bs, int start, int len) {
-    hexDump("", name, bs, start, len);
-}
+epicsShareFunc
+std::ostream& operator<<(std::ostream& strm, const HexDump& hex)
+{
+    size_t len = std::min(hex.buflen, hex._limit);
+    // find address width in hex chars
+    // find bit width, rounded up to 8 bits, divide down to bytes
+    size_t addrwidth = bits2bytes(ilog2(len))*2u;
 
-void hexDump(std::string const & prologue, string const & name, const int8 *bs,
-             int start, int len) {
+    for(size_t i=0; i<len; i++)
+    {
+        unsigned val = hex.buf[i]&0xff;
+        size_t col = i%hex._perLine;
 
-    stringstream header;
-
-    header<<prologue<<endl<<"Hexdump ["<<name<<"] size = "<<len;
-
-    string out(header.str());
-
-    string chars;
-
-    for(int i = start; i<(start+len); i++) {
-        if(((i-start)%16)==0) {
-            out += chars;
-            out += '\n';
-            chars.erase();
+        if(col==0) {
+            // first address of this row
+            strm<<"0x"<<std::hex<<std::setw(addrwidth)<<std::setfill('0')<<i;
         }
-
-        chars += toAscii(bs[i]);
-
-        out += toHex(bs[i]);
-
-        if(((i-start)%4)==3) {
-            chars += ' ';
-            out += ' ';
+        if(col%hex._groupBy == 0) {
+            strm<<' ';
         }
+        strm<<std::hex<<std::setw(2)<<std::setfill('0')<<val;
+        if(col+1u==hex._perLine && i+1u!=len)
+            strm<<'\n';
     }
-
-    if(len%16!=0) {
-        int pad = 0;
-        int delta_bytes = 16-(len%16);
-
-        //rest of line (no of bytes)
-        //each byte takes two chars plus one ws
-        pad = delta_bytes*3;
-
-        //additional whitespaces after four bytes
-        pad += (delta_bytes/4);
-        pad++;
-
-        for(int i = 0; i<pad; i++)
-            chars.insert(0, " ");
-    }
-
-    out += chars;
-    cout<<out<<endl;
+    if(len==hex._limit && len<hex.buflen)
+        strm<<" ...";
+    strm<<'\n';
+    return strm;
 }
 
 }
diff --git a/src/utils/pv/hexDump.h b/src/utils/pv/hexDump.h
index fa5f014..d1f4d7c 100644
--- a/src/utils/pv/hexDump.h
+++ b/src/utils/pv/hexDump.h
@@ -7,6 +7,8 @@
 #ifndef HEXDUMP_H_
 #define HEXDUMP_H_
 
+#include <ostream>
+
 #ifdef epicsExportSharedSymbols
 #   define hexDumpEpicsExportSharedSymbols
 #   undef epicsExportSharedSymbols
@@ -22,35 +24,34 @@
 #include <shareLib.h>
 
 namespace epics {
+namespace pvData {
+class ByteBuffer;
+}
 namespace pvAccess {
 
-/**
- * Output a buffer in hex format.
- * @param name  name (description) of the message.
- * @param bs    buffer to dump
- * @param len   first bytes (length) to dump.
- */
-epicsShareFunc void hexDump(std::string const & name, const epics::pvData::int8 *bs, int len);
+class epicsShareClass HexDump {
+    const char* buf;
+    size_t buflen;
+    size_t _limit;
+    unsigned _groupBy;
+    unsigned _perLine;
+public:
+    HexDump(const char* buf, size_t len);
+    explicit HexDump(const pvData::ByteBuffer& buf, size_t size=(size_t)-1, size_t offset=0u);
+    ~HexDump();
 
-/**
- * Output a buffer in hex format.
- * @param[in] name  name (description) of the message.
- * @param[in] bs    buffer to dump
- * @param[in] start dump message using given offset.
- * @param[in] len   first bytes (length) to dump.
- */
-epicsShareFunc void hexDump(std::string const & name, const epics::pvData::int8 *bs, int start, int len);
+    //! safety limit on max bytes printed
+    inline HexDump& limit(size_t n=(size_t)-1)        { _limit = n; return *this; }
+    //! insert a space after this many bytes
+    inline HexDump& bytesPerGroup(size_t n=(size_t)-1) { _groupBy = n; return *this; }
+    //! start a new line after this many bytes
+    inline HexDump& bytesPerLine(size_t n=(size_t)-1) { _perLine = n; return *this; }
 
-/**
- * Output a buffer in hex format.
- * @param[in] prologue string to prefixed to debug output, can be <code>null</code>
- * @param[in] name  name (description) of the message.
- * @param[in] bs    buffer to dump
- * @param[in] start dump message using given offset.
- * @param[in] len   first bytes (length) to dump.
- */
-epicsShareFunc void hexDump(std::string const & prologue, std::string const & name,
-                            const epics::pvData::int8 *bs, int start, int len);
+    friend std::ostream& operator<<(std::ostream& strm, const HexDump& hex);
+};
+
+epicsShareFunc
+std::ostream& operator<<(std::ostream& strm, const HexDump& hex);
 
 }
 }
diff --git a/testApp/remote/testCodec.cpp b/testApp/remote/testCodec.cpp
index 74cb62c..8af85f2 100644
--- a/testApp/remote/testCodec.cpp
+++ b/testApp/remote/testCodec.cpp
@@ -372,8 +372,6 @@ public:
     void setRemoteTransportReceiveBufferSize(
         std::size_t remoteTransportReceiveBufferSize)  {}
 
-    void changedTransport() {}
-
     void flushSendQueue() { };
 
     bool verify(epics::pvData::int32 timeoutMs) {
@@ -382,8 +380,6 @@ public:
 
     void verified(epics::pvData::Status const &) {}
 
-    void aliveNotification() {}
-
     void authNZMessage(epics::pvData::PVStructure::shared_pointer const & data) {}
 
 
@@ -483,7 +479,7 @@ private:
         TestCodec codec(DEFAULT_BUFFER_SIZE,DEFAULT_BUFFER_SIZE);
 
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x01);
         codec._readBuffer->put((int8_t)0x23);
         codec._readBuffer->putInt(0x456789AB);
@@ -506,8 +502,8 @@ private:
 
         PVAMessage header = codec._receivedControlMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
 
         testOk(codec._invalidDataStreamCount == 0,
                "%s: codec._invalidDataStreamCount == 0",
@@ -523,13 +519,13 @@ private:
 
         // two at the time, app and control
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x00);
         codec._readBuffer->put((int8_t)0x20);
         codec._readBuffer->putInt(0x00000000);
 
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x81);
         codec._readBuffer->put((int8_t)0xEE);
         codec._readBuffer->putInt(0xDDCCBBAA);
@@ -553,8 +549,8 @@ private:
         // app, no payload
         header = codec._receivedAppMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)0x00,
                "%s: header._flags == 0x00", CURRENT_FUNCTION);
         testOk(header._command == (int8_t)0x20,
@@ -565,8 +561,8 @@ private:
         // control
         header = codec._receivedControlMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)0x81,
                "%s: header._flags == 0x81", CURRENT_FUNCTION);
         testOk(header._command == (int8_t)0xEE,
@@ -585,7 +581,7 @@ private:
         TestCodec codec(DEFAULT_BUFFER_SIZE,DEFAULT_BUFFER_SIZE);
 
         codec._readBuffer->put((int8_t)00);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x01);
         codec._readBuffer->put((int8_t)0x23);
         codec._readBuffer->putInt(0x456789AB);
@@ -621,7 +617,7 @@ private:
         {
             TestCodec codec(DEFAULT_BUFFER_SIZE,DEFAULT_BUFFER_SIZE);
             codec._readBuffer->put(PVA_MAGIC);
-            codec._readBuffer->put(PVA_VERSION);
+            codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
             codec._readBuffer->put(invalidFlagsValues[i]);
             codec._readBuffer->put((int8_t)0x23);
             //codec._readBuffer->putInt(0);
@@ -653,7 +649,7 @@ private:
         TestCodec codec(DEFAULT_BUFFER_SIZE,DEFAULT_BUFFER_SIZE);
 
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x80);
         codec._readBuffer->put((int8_t)0x23);
         codec._readBuffer->putInt(0x456789AB);
@@ -682,7 +678,7 @@ private:
         TestCodec codec(DEFAULT_BUFFER_SIZE,DEFAULT_BUFFER_SIZE);
 
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x01);
         codec._readBuffer->flip();
 
@@ -724,8 +720,8 @@ private:
         // app, no payload
         PVAMessage header = codec._receivedControlMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)0x01,
                "%s: header._flags == 0x01", CURRENT_FUNCTION);
         testOk(header._command == (int8_t)0x23,
@@ -744,7 +740,7 @@ private:
         codec._readPayload = true;
 
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x80);
         codec._readBuffer->put((int8_t)0x23);
         codec._readBuffer->putInt(1); // size
@@ -790,7 +786,7 @@ private:
         codec._readPayload = true;
 
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x80);
         codec._readBuffer->put((int8_t)0x23);
         const int32_t payloadSize1 = 2;
@@ -806,7 +802,7 @@ private:
 
 
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x80);
         codec._readBuffer->put((int8_t)0x45);
 
@@ -912,7 +908,7 @@ private:
 
 
                 _codec._readBuffer->put(PVA_MAGIC);
-                _codec._readBuffer->put(PVA_VERSION);
+                _codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
                 _codec._readBuffer->put((int8_t)0x80);
                 _codec._readBuffer->put((int8_t)0x45);
                 _codec._readBuffer->putInt(_payloadSize2);
@@ -958,7 +954,7 @@ private:
 
         // 1st
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x90);
         codec._readBuffer->put((int8_t)0x01);
 
@@ -971,7 +967,7 @@ private:
 
         // 2nd
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0xB0);
         codec._readBuffer->put((int8_t)0x01);
 
@@ -983,14 +979,14 @@ private:
 
         // control in between
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x81);
         codec._readBuffer->put((int8_t)0xEE);
         codec._readBuffer->putInt(0xDDCCBBAA);
 
         // 3rd
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0xB0);
         codec._readBuffer->put((int8_t)0x01);
 
@@ -1002,7 +998,7 @@ private:
 
         // 4t (last)
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0xA0);
         codec._readBuffer->put((int8_t)0x01);
 
@@ -1057,8 +1053,8 @@ private:
 
         msg = codec._receivedControlMessages[0];
 
-        testOk(msg._version == PVA_VERSION,
-               "%s: msg._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(msg._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: msg._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(msg._flags == (int8_t)0x81,
                "%s: msg._flags == 0x81", CURRENT_FUNCTION);
         testOk(msg._command == (int8_t)0xEE,
@@ -1078,7 +1074,7 @@ private:
 
         // 1st
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x90);
         codec._readBuffer->put((int8_t)0x01);
 
@@ -1091,7 +1087,7 @@ private:
 
         // 2nd
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         // invalid flag, should be 0xB0
         codec._readBuffer->put((int8_t)0x90);
         codec._readBuffer->put((int8_t)0x01);
@@ -1104,14 +1100,14 @@ private:
 
         // control in between
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x81);
         codec._readBuffer->put((int8_t)0xEE);
         codec._readBuffer->putInt(0xDDCCBBAA);
 
         // 3rd
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0xB0);
         codec._readBuffer->put((int8_t)0x01);
 
@@ -1123,7 +1119,7 @@ private:
 
         // 4t (last)
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0xA0);
         codec._readBuffer->put((int8_t)0x01);
 
@@ -1172,7 +1168,7 @@ private:
 
         // 1st
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x90);
         codec._readBuffer->put((int8_t)0x01);
 
@@ -1190,7 +1186,7 @@ private:
 
         // 2nd
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0xB0);
         codec._readBuffer->put((int8_t)0x01);
 
@@ -1209,7 +1205,7 @@ private:
 
         // 3rd
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0xB0);
         codec._readBuffer->put((int8_t)0x01);
 
@@ -1227,7 +1223,7 @@ private:
 
         // 4t (last)
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0xA0);
         codec._readBuffer->put((int8_t)0x01);
 
@@ -1339,7 +1335,7 @@ private:
 
                         // 1st
                         codec._readBuffer->put(PVA_MAGIC);
-                        codec._readBuffer->put(PVA_VERSION);
+                        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
                         codec._readBuffer->put((int8_t)0x90);
                         codec._readBuffer->put((int8_t)0x01);
 
@@ -1357,7 +1353,7 @@ private:
 
                         // 2nd
                         codec._readBuffer->put(PVA_MAGIC);
-                        codec._readBuffer->put(PVA_VERSION);
+                        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
                         codec._readBuffer->put((int8_t)0xB0);
                         codec._readBuffer->put((int8_t)0x01);
 
@@ -1377,7 +1373,7 @@ private:
 
                         // 3rd
                         codec._readBuffer->put(PVA_MAGIC);
-                        codec._readBuffer->put(PVA_VERSION);
+                        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
                         codec._readBuffer->put((int8_t)0xA0);
                         codec._readBuffer->put((int8_t)0x01);
 
@@ -1499,8 +1495,8 @@ private:
 
         PVAMessage header = codec._receivedControlMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)((EPICS_BYTE_ORDER == EPICS_ENDIAN_BIG ? 0x80 : 0x00) | 0x01),
                "%s: header._flags == 0x(0|8)1", CURRENT_FUNCTION);
         testOk(header._command == (int8_t)0x23,
@@ -1537,8 +1533,8 @@ private:
         // app, no payload
         header = codec._receivedAppMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)0x00,
                "%s: header._flags == 0x00", CURRENT_FUNCTION);
         testOk(header._command == (int8_t)0x20,
@@ -1549,8 +1545,8 @@ private:
         // control
         header = codec._receivedControlMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)0x81,
                "%s: header._flags == 0x81", CURRENT_FUNCTION);
         testOk(header._command == (int8_t)0xEE,
@@ -1878,7 +1874,7 @@ private:
         codec._disconnected = true;
 
         codec._readBuffer->put(PVA_MAGIC);
-        codec._readBuffer->put(PVA_VERSION);
+        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
         codec._readBuffer->put((int8_t)0x01);
         codec._readBuffer->put((int8_t)0x23);
         codec._readBuffer->putInt(0x456789AB);
@@ -1953,7 +1949,7 @@ private:
 
                         // 1st
                         codec._readBuffer->put(PVA_MAGIC);
-                        codec._readBuffer->put(PVA_VERSION);
+                        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
                         codec._readBuffer->put((int8_t)0x90);
                         codec._readBuffer->put((int8_t)0x01);
 
@@ -1971,7 +1967,7 @@ private:
 
                         // 2nd
                         codec._readBuffer->put(PVA_MAGIC);
-                        codec._readBuffer->put(PVA_VERSION);
+                        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
                         codec._readBuffer->put((int8_t)0xB0);
                         codec._readBuffer->put((int8_t)0x01);
 
@@ -1991,7 +1987,7 @@ private:
 
                         // 3rd
                         codec._readBuffer->put(PVA_MAGIC);
-                        codec._readBuffer->put(PVA_VERSION);
+                        codec._readBuffer->put(PVA_CLIENT_PROTOCOL_REVISION);
                         codec._readBuffer->put((int8_t)0xA0);
                         codec._readBuffer->put((int8_t)0x01);
 
@@ -2156,8 +2152,8 @@ private:
         // app, no payload
         PVAMessage header = codec._receivedAppMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)((EPICS_BYTE_ORDER == EPICS_ENDIAN_BIG ? 0x80 : 0x00) | 0x00),
                "%s: header._flags == 0x(0|8)0", CURRENT_FUNCTION);
         testOk(header._command == (int8_t)0x20,
@@ -2168,8 +2164,8 @@ private:
         // control
         header = codec._receivedControlMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)((EPICS_BYTE_ORDER == EPICS_ENDIAN_BIG ? 0x80 : 0x00) | 0x01),
                "%s: header._flags == 0x(0|8)1", CURRENT_FUNCTION);
         testOk(header._command == (int8_t)0xEE,
@@ -2293,8 +2289,8 @@ private:
         // app, no payload
         PVAMessage header = codec._receivedAppMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)((EPICS_BYTE_ORDER == EPICS_ENDIAN_BIG ? 0x80 : 0x00) | 0x00),
                "%s: header._flags == 0x(0|8)0", CURRENT_FUNCTION);
         testOk(header._command == 0x20,
@@ -2306,8 +2302,8 @@ private:
         // control
         header = codec._receivedControlMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)((EPICS_BYTE_ORDER == EPICS_ENDIAN_BIG ? 0x80 : 0x00) | 0x01),
                "%s: header._flags == 0x(0|8)1", CURRENT_FUNCTION);
         testOk(header._command == (int8_t)0xEE,
@@ -2363,8 +2359,8 @@ private:
 
         header = codec._receivedControlMessages[1];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)((EPICS_BYTE_ORDER == EPICS_ENDIAN_BIG ? 0x80 : 0x00) | 0x01),
                "%s: header._flags == 0x(0|8)1", CURRENT_FUNCTION);
         testOk(header._command == (int8_t)0xEE,
@@ -2443,8 +2439,8 @@ private:
         // app
         PVAMessage header = codec._receivedAppMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)0x80,
                "%s: header._flags == 0x80", CURRENT_FUNCTION);
         testOk(header._command == (int8_t)0x12,
@@ -2640,8 +2636,8 @@ private:
         // app
         PVAMessage header = codec._receivedAppMessages[0];
 
-        testOk(header._version == PVA_VERSION,
-               "%s: header._version == PVA_VERSION", CURRENT_FUNCTION);
+        testOk(header._version == PVA_CLIENT_PROTOCOL_REVISION,
+               "%s: header._version == PVA_CLIENT_PROTOCOL_REVISION", CURRENT_FUNCTION);
         testOk(header._flags == (int8_t)((EPICS_BYTE_ORDER == EPICS_ENDIAN_BIG ? 0x80 : 0x00) | 0x10),
                "%s: header._flags == (int8_t)(0x(0|8)0 | 0x10)",
                CURRENT_FUNCTION);
diff --git a/testApp/utils/testHexDump.cpp b/testApp/utils/testHexDump.cpp
index d4cf207..bd10005 100644
--- a/testApp/utils/testHexDump.cpp
+++ b/testApp/utils/testHexDump.cpp
@@ -1,6 +1,9 @@
-#include <epicsUnitTest.h>
+
+#include <sstream>
+
 #include <testMain.h>
 
+#include <pv/pvUnitTest.h>
 #include <pv/hexDump.h>
 
 using namespace epics::pvData;
@@ -8,19 +11,16 @@ using namespace epics::pvAccess;
 
 MAIN(testHexDump)
 {
-    testPlan(3);
+    testPlan(1);
     testDiag("Tests for hexDump");
 
-    char TO_DUMP[] = "pvAccess dump test\0\1\2\3\4\5\6\254\255\256";
+    char TO_DUMP[] = "pvAccess dump test\0\1\2\3\4\5\6\xfd\xfe\xff";
 
-    hexDump("test", (int8*)TO_DUMP, 18+9);
-    testPass("Entire array");
+    std::ostringstream msg;
+    msg<<HexDump(TO_DUMP, sizeof(TO_DUMP)-1);
 
-    hexDump("only text", (int8*)TO_DUMP, 18);
-    testPass("Only text");
-
-    hexDump("22 byte test", (int8*)TO_DUMP, 22);
-    testPass("22 bytes test");
+    testEqual(msg.str(), "0x00 70764163 63657373 2064756d 70207465\n"
+                         "0x10 73740001 02030405 06fdfeff\n");
 
     return testDone();
 }