diff --git a/src/ca/tcpiiu.cpp b/src/ca/tcpiiu.cpp
index d93f5ad53..b280e8202 100644
--- a/src/ca/tcpiiu.cpp
+++ b/src/ca/tcpiiu.cpp
@@ -181,15 +181,23 @@ void tcpSendThread::run ()
     }
 
     this->iiu.sendDog.cancel ();
-
-    // wakeup user threads blocking for send backlog to be reduced
-    // and wait for them to stop using this IIU
-    this->iiu.flushBlockEvent.signal ();
-    while ( this->iiu.blockingForFlush ) {
-        epicsThreadSleep ( 0.1 );
-    }
+    this->iiu.recvDog.cancel ();
 
     this->iiu.recvThread.exitWait ();
+
+    // user threads blocking for send backlog to be reduced
+    // will abort their attempt to get space if 
+    // the state of the tcpiiu changes from connected to a
+    // disconnecting state. Nevertheless, we need to wait
+    // for them to finish prior to destroying the IIU.
+    {
+        epicsGuard < epicsMutex > guard ( this->iiu.mutex );
+        while ( this->iiu.blockingForFlush ) {
+            epicsGuardRelease < epicsMutex > unguard ( guard );
+            epicsThreadSleep ( 0.1 );
+        }
+    }
+
     this->thread.exitWaitRelease ();
 
     this->iiu.cacRef.destroyIIU ( this->iiu );
@@ -288,6 +296,19 @@ void tcpiiu::recvBytes (
             // bad file descriptor
             if ( this->state != iiucs_connected && 
                     this->state != iiucs_clean_shutdown ) {
+                // the replacable printf handler isnt called here
+                // because it reqires a callback lock which probably
+                // isnt appropriate here
+                char name[64];
+                this->hostNameCacheInstance.hostName ( 
+                    name, sizeof ( name ) );
+                char sockErrBuf[64];
+                epicsSocketConvertErrnoToString ( 
+                    sockErrBuf, sizeof ( sockErrBuf ) );
+                errlogPrintf (
+                    "Unexpected problem with CA circuit to"
+                    " server \"%s\" was \"%s\" - disconnecting\n", 
+                            name, sockErrBuf );
                 stat.bytesCopied = 0u;
                 stat.circuitState = swioLocalAbort;
                 return;
@@ -396,17 +417,6 @@ void tcpRecvThread::run ()
                     break;
                 }
                 else if ( stat.circuitState == swioLocalAbort ) {
-                    callbackManager mgr ( this->ctxNotify, this->cbMutex );
-                    epicsGuard < epicsMutex > guard ( this->iiu.mutex );
-                    char name[64];
-                    this->iiu.hostName ( guard, name, sizeof ( name ) );
-                    char sockErrBuf[64];
-                    epicsSocketConvertErrnoToString ( 
-                        sockErrBuf, sizeof ( sockErrBuf ) );
-                    this->iiu.printf ( mgr.cbGuard,
-                        "Unexpected problem with CA circuit to",
-                        " server \"%s\" was \"%s\" - disconnecting\n", 
-                                name, sockErrBuf );
                     break;
                 }
                 else {
@@ -472,16 +482,6 @@ void tcpRecvThread::run ()
                         this->iiu.initiateAbortShutdown ( mgr, guard );
                     }
                     else if ( stat.circuitState == swioLocalAbort ) {
-                        epicsGuard < epicsMutex > guard ( this->iiu.mutex );
-                        char name[64];
-                        this->iiu.hostName ( guard, name, sizeof ( name ) );
-                        char sockErrBuf[64];
-                        epicsSocketConvertErrnoToString ( 
-                            sockErrBuf, sizeof ( sockErrBuf ) );
-                        this->iiu.printf ( mgr.cbGuard,
-                            "Unexpected problem with CA circuit to",
-                            " server \"%s\" was \"%s\" - disconnecting\n", 
-                                    name, sockErrBuf );
                         break;
                     }
                     else {
@@ -746,6 +746,7 @@ void tcpiiu::initiateCleanShutdown (
     if ( this->state == iiucs_connected ) {
         this->state = iiucs_clean_shutdown;
         this->sendThreadFlushEvent.signal ();
+        this->flushBlockEvent.signal ();
     }
 }
 
@@ -756,6 +757,7 @@ void tcpiiu::disconnectNotify ()
         this->state = iiucs_disconnected;
     }
     this->sendThreadFlushEvent.signal ();
+    this->flushBlockEvent.signal ();
 }
 
 void tcpiiu::responsiveCircuitNotify ( 
@@ -807,6 +809,7 @@ void tcpiiu::unresponsiveCircuitNotify (
         this->unresponsiveCircuit = true;
         this->echoRequestPending = true;
         this->sendThreadFlushEvent.signal ();
+        this->flushBlockEvent.signal ();
 
         this->recvDog.cancel ();
         this->sendDog.cancel ();
@@ -898,6 +901,7 @@ void tcpiiu::initiateAbortShutdown (
         // wake up the send thread if it isnt blocking in send()
         //
         this->sendThreadFlushEvent.signal ();
+        this->flushBlockEvent.signal ();
     }
 
     // Disconnect all channels immediately from the timer thread
@@ -931,6 +935,8 @@ tcpiiu::~tcpiiu ()
 {
     this->sendThread.exitWait ();
     this->recvThread.exitWait ();
+    this->sendDog.cancel ();
+    this->recvDog.cancel ();
 
     if ( ! this->socketHasBeenClosed ) {
         epicsSocketDestroy ( this->sock );
@@ -1290,7 +1296,11 @@ void tcpiiu::writeRequest ( epicsGuard < epicsMutex > & guard, // X aCC 431
     nciu &chan, unsigned type, arrayElementCount nElem, const void *pValue )
 {
     guard.assertIdenticalMutex ( this->mutex );
-
+    // there are situations where the circuit is disconnected, but
+    // the channel does not know this yet
+    if ( this->state != iiucs_connected ) {
+        throw cacChannel::notConnected ();
+    }
     comQueSendMsgMinder minder ( this->sendQue, guard );
     this->sendQue.insertRequestWithPayLoad ( CA_PROTO_WRITE,  
         type, nElem, chan.getSID(guard), chan.getCID(guard), pValue,
@@ -1308,6 +1318,11 @@ void tcpiiu::writeNotifyRequest ( epicsGuard < epicsMutex > & guard, // X aCC 43
     if ( ! this->ca_v41_ok ( guard ) ) {
         throw cacChannel::unsupportedByService();
     }
+    // there are situations where the circuit is disconnected, but
+    // the channel does not know this yet
+    if ( this->state != iiucs_connected ) {
+        throw cacChannel::notConnected ();
+    }
     comQueSendMsgMinder minder ( this->sendQue, guard );
     this->sendQue.insertRequestWithPayLoad ( CA_PROTO_WRITE_NOTIFY,  
         type, nElem, chan.getSID(guard), io.getId(), pValue,
@@ -1320,7 +1335,11 @@ void tcpiiu::readNotifyRequest ( epicsGuard < epicsMutex > & guard, // X aCC 431
                                unsigned dataType, arrayElementCount nElem )
 {
     guard.assertIdenticalMutex ( this->mutex );
-
+    // there are situations where the circuit is disconnected, but
+    // the channel does not know this yet
+    if ( this->state != iiucs_connected ) {
+        throw cacChannel::notConnected ();
+    }
     if ( INVALID_DB_REQ ( dataType ) ) {
         throw cacChannel::badType ();
     }
@@ -1351,6 +1370,11 @@ void tcpiiu::createChannelRequest (
 {
     guard.assertIdenticalMutex ( this->mutex );
 
+    if ( this->state != iiucs_connected && 
+        this->state != iiucs_connecting ) {
+        return;
+    }
+
     const char *pName;
     unsigned nameLength;
     ca_uint32_t identity;
@@ -1394,7 +1418,11 @@ void tcpiiu::clearChannelRequest ( epicsGuard < epicsMutex > & guard, // X aCC 4
                                   ca_uint32_t sid, ca_uint32_t cid )
 {
     guard.assertIdenticalMutex ( this->mutex );
-
+    // there are situations where the circuit is disconnected, but
+    // the channel does not know this yet
+    if ( this->state != iiucs_connected ) {
+        return;
+    }
     comQueSendMsgMinder minder ( this->sendQue, guard );
     this->sendQue.insertRequestHeader ( 
         CA_PROTO_CLEAR_CHANNEL, 0u, 
@@ -1412,8 +1440,10 @@ void tcpiiu::subscriptionRequest (
     nciu & chan, netSubscription & subscr )
 {
     guard.assertIdenticalMutex ( this->mutex );
-
-    if ( ! chan.isConnected ( guard ) ) {
+    // there are situations where the circuit is disconnected, but
+    // the channel does not know this yet
+    if ( this->state != iiucs_connected && 
+        this->state != iiucs_connecting ) {
         return;
     }
     unsigned mask = subscr.getMask(guard);
@@ -1456,12 +1486,14 @@ void tcpiiu::subscriptionRequest (
 // this routine return void because if this internally fails the best response
 // is to try again the next time that we reconnect
 //
-void tcpiiu::subscriptionUpdateRequest ( epicsGuard < epicsMutex > & guard, // X aCC 431
-                                  nciu & chan, netSubscription & subscr )
+void tcpiiu::subscriptionUpdateRequest ( 
+    epicsGuard < epicsMutex > & guard, // X aCC 431
+    nciu & chan, netSubscription & subscr )
 {
     guard.assertIdenticalMutex ( this->mutex );
-
-    if ( ! chan.isConnected ( guard ) ) {
+    // there are situations where the circuit is disconnected, but
+    // the channel does not know this yet
+    if ( this->state != iiucs_connected ) {
         return;
     }
     arrayElementCount nElem = subscr.getCount ( guard );
@@ -1493,7 +1525,11 @@ void tcpiiu::subscriptionCancelRequest ( epicsGuard < epicsMutex > & guard, // X
                              nciu & chan, netSubscription & subscr )
 {
     guard.assertIdenticalMutex ( this->mutex );
-
+    // there are situations where the circuit is disconnected, but
+    // the channel does not know this yet
+    if ( this->state != iiucs_connected ) {
+        return;
+    }
     comQueSendMsgMinder minder ( this->sendQue, guard );
     this->sendQue.insertRequestHeader ( 
         CA_PROTO_EVENT_CANCEL, 0u, 
@@ -1554,6 +1590,13 @@ void tcpiiu::eliminateExcessiveSendBacklog (
 {
     mutualExclusionGuard.assertIdenticalMutex ( this->mutex );
 
+    // this is used to slow down applications that use too much
+    // send cache, but this is inappropriate when the circuit hasnt 
+    // connected yet.
+    if ( this->state == iiucs_connecting ) {
+        return;
+    }
+
     if ( this->sendQue.flushBlockThreshold ( 0u ) ) {
         this->flushRequest ( mutualExclusionGuard );
         // the process thread is not permitted to flush as this
@@ -1568,8 +1611,15 @@ void tcpiiu::eliminateExcessiveSendBacklog (
             // pointer to this cac might become invalid            
             assert ( this->blockingForFlush < UINT_MAX );
             this->blockingForFlush++;
-            while ( this->sendQue.flushBlockThreshold(0u) && 
-                    this->state == iiucs_connected ) {
+            while ( this->sendQue.flushBlockThreshold(0u) ) {
+
+                // fail the users request if we have a disconnected
+                // or unresponsive circuit
+                if ( this->state != iiucs_connected || 
+                        this->unresponsiveCircuit ) {
+                    throw cacChannel::notConnected ();
+                }
+
                 epicsGuardRelease < epicsMutex > autoRelease ( 
                         mutualExclusionGuard );
                 if ( pCallbackGuard ) {