diff --git a/client/CClient.cpp b/client/CClient.cpp
index 453d6d45..83d2164f 100644
--- a/client/CClient.cpp
+++ b/client/CClient.cpp
@@ -13,6 +13,7 @@
 #include "CTimerThread.h"
 #include "XThread.h"
 #include "CLog.h"
+#include "CStopwatch.h"
 #include "TMethodJob.h"
 #include <memory>
 
@@ -301,23 +302,36 @@ CClient::runSession(void*)
 		m_compressMouse = false;
 
 		// handle messages from server
+		CStopwatch heartbeat;
 		for (;;) {
 			// if no input is pending then flush compressed mouse motion
 			if (input->getSize() == 0) {
 				flushCompressedMouse();
 			}
 
-			// wait for reply
+			// wait for a message
 			log((CLOG_DEBUG2 "waiting for message"));
 			UInt8 code[4];
-			UInt32 n = input->read(code, 4);
+			UInt32 n = input->read(code, 4, kHeartRate);
 
-			// verify we got an entire code
+			// check if server hungup
 			if (n == 0) {
 				log((CLOG_NOTE "server disconnected"));
-				// server hungup
 				break;
 			}
+
+			// check for time out
+			if (n == (UInt32)-1 || heartbeat.getTime() > kHeartRate) {
+				// send heartbeat
+				CProtocolUtil::writef(m_output, kMsgCNoop);
+				heartbeat.reset();
+				if (n == (UInt32)-1) {
+					// no message to process
+					continue;
+				}
+			}
+
+			// verify we got an entire code
 			if (n != 4) {
 				// client sent an incomplete message
 				log((CLOG_ERR "incomplete message from server"));
@@ -347,6 +361,10 @@ CClient::runSession(void*)
 			else if (memcmp(code, kMsgDKeyRepeat, 4) == 0) {
 				onKeyRepeat();
 			}
+			else if (memcmp(code, kMsgCNoop, 4) == 0) {
+				// accept and discard no-op
+				continue;
+			}
 			else if (memcmp(code, kMsgCEnter, 4) == 0) {
 				onEnter();
 			}
diff --git a/http/CHTTPProtocol.cpp b/http/CHTTPProtocol.cpp
index e49bdd00..cea0d64c 100644
--- a/http/CHTTPProtocol.cpp
+++ b/http/CHTTPProtocol.cpp
@@ -468,7 +468,7 @@ CHTTPProtocol::readLine(IInputStream* stream, CString& tmpBuffer)
 
 		// read more from stream
 		char buffer[4096];
-		UInt32 n = stream->read(buffer, sizeof(buffer));
+		UInt32 n = stream->read(buffer, sizeof(buffer), -1.0);
 		if (n == 0) {
 			// stream is empty.  return what's leftover.
 			CString line = tmpBuffer;
@@ -514,7 +514,7 @@ CHTTPProtocol::readBlock(IInputStream* stream,
 		if (n > numBytes) {
 			n = numBytes;
 		}
-		n = stream->read(buffer, n);
+		n = stream->read(buffer, n, -1.0);
 
 		// if stream is empty then return what we've got so far
 		if (n == 0) {
diff --git a/io/CBufferedInputStream.cpp b/io/CBufferedInputStream.cpp
index 28c6e7a5..06f553ea 100644
--- a/io/CBufferedInputStream.cpp
+++ b/io/CBufferedInputStream.cpp
@@ -2,6 +2,7 @@
 #include "CLock.h"
 #include "CMutex.h"
 #include "CThread.h"
+#include "CStopwatch.h"
 #include "IJob.h"
 #include "XIO.h"
 #include <cstring>
@@ -43,15 +44,19 @@ CBufferedInputStream::hangup()
 }
 
 UInt32
-CBufferedInputStream::readNoLock(void* dst, UInt32 n)
+CBufferedInputStream::readNoLock(void* dst, UInt32 n, double timeout)
 {
 	if (m_closed) {
 		throw XIOClosed();
 	}
 
-	// wait for data (or hangup)
+	// wait for data, hangup, or timeout
+	CStopwatch timer(true);
 	while (!m_hungup && m_empty == true) {
-		m_empty.wait();
+		if (!m_empty.wait(timer, timeout)) {
+			// timed out
+			return (UInt32)-1;
+		}
 	}
 
 	// read data
@@ -98,10 +103,10 @@ CBufferedInputStream::close()
 }
 
 UInt32
-CBufferedInputStream::read(void* dst, UInt32 n)
+CBufferedInputStream::read(void* dst, UInt32 n, double timeout)
 {
 	CLock lock(m_mutex);
-	return readNoLock(dst, n);
+	return readNoLock(dst, n, timeout);
 }
 
 UInt32
diff --git a/io/CBufferedInputStream.h b/io/CBufferedInputStream.h
index f47658f3..22ded242 100644
--- a/io/CBufferedInputStream.h
+++ b/io/CBufferedInputStream.h
@@ -26,7 +26,7 @@ public:
 	void				hangup();
 
 	// same as read() but caller must lock the mutex
-	UInt32				readNoLock(void*, UInt32 count);
+	UInt32				readNoLock(void*, UInt32 count, double timeout);
 
 	// accessors
 
@@ -36,7 +36,7 @@ public:
 	// IInputStream overrides
 	// these all lock the mutex for their duration
 	virtual void		close();
-	virtual UInt32		read(void*, UInt32 count);
+	virtual UInt32		read(void*, UInt32 count, double timeout);
 	virtual UInt32		getSize() const;
 
 private:
diff --git a/io/CInputStreamFilter.h b/io/CInputStreamFilter.h
index 85487226..bb25a261 100644
--- a/io/CInputStreamFilter.h
+++ b/io/CInputStreamFilter.h
@@ -14,7 +14,7 @@ public:
 
 	// IInputStream overrides
 	virtual void		close() = 0;
-	virtual UInt32		read(void*, UInt32 maxCount) = 0;
+	virtual UInt32		read(void*, UInt32 maxCount, double timeout) = 0;
 	virtual UInt32		getSize() const = 0;
 
 protected:
diff --git a/io/IInputStream.h b/io/IInputStream.h
index f025ed40..fc5abaa3 100644
--- a/io/IInputStream.h
+++ b/io/IInputStream.h
@@ -13,8 +13,11 @@ public:
 
 	// read up to maxCount bytes into buffer, return number read.
 	// blocks if no data is currently available.  if buffer is NULL
-	// then the data is discarded.
-	virtual UInt32		read(void* buffer, UInt32 maxCount) = 0;
+	// then the data is discarded.  returns (UInt32)-1 if there's
+	// no data for timeout seconds;  if timeout < 0 then it blocks
+	// until data is available.
+	// (cancellation point)
+	virtual UInt32		read(void* buffer, UInt32 maxCount, double timeout) = 0;
 
 	// accessors
 
diff --git a/server/CMSWindowsPrimaryScreen.cpp b/server/CMSWindowsPrimaryScreen.cpp
index e35d2811..1631ab7f 100644
--- a/server/CMSWindowsPrimaryScreen.cpp
+++ b/server/CMSWindowsPrimaryScreen.cpp
@@ -386,21 +386,27 @@ CMSWindowsPrimaryScreen::onOpenDisplay()
 	// initialize hook library
 	m_init(m_threadID);
 
-	// install the screen saver hook
-	if (m_installScreenSaver != NULL) {
-		m_installScreenSaver();
-	}
+	try {
+		// install the screen saver hook
+		if (m_installScreenSaver != NULL) {
+			m_installScreenSaver();
+		}
 
-	// get the input desktop and switch to it
-	if (m_is95Family) {
-		if (!openDesktop()) {
-			throw XScreenOpenFailure();
+		// get the input desktop and switch to it
+		if (m_is95Family) {
+			if (!openDesktop()) {
+				throw XScreenOpenFailure();
+			}
+		}
+		else {
+			if (!switchDesktop(openInputDesktop())) {
+				throw XScreenOpenFailure();
+			}
 		}
 	}
-	else {
-		if (!switchDesktop(openInputDesktop())) {
-			throw XScreenOpenFailure();
-		}
+	catch (...) {
+		m_cleanup();
+		throw;
 	}
 }
 
diff --git a/server/CServer.cpp b/server/CServer.cpp
index 6ae97436..5e7004ba 100644
--- a/server/CServer.cpp
+++ b/server/CServer.cpp
@@ -42,6 +42,7 @@ CServer::CServer(const CString& serverName) :
 	m_active(NULL),
 	m_primaryInfo(NULL),
 	m_seqNum(0),
+	m_activeSaver(NULL),
 	m_httpServer(NULL),
 	m_httpAvailable(&m_mutex, s_httpMaxSimultaneousRequests)
 {
diff --git a/server/CServerProtocol1_0.cpp b/server/CServerProtocol1_0.cpp
index 54eaf81e..ad6f559d 100644
--- a/server/CServerProtocol1_0.cpp
+++ b/server/CServerProtocol1_0.cpp
@@ -8,6 +8,7 @@
 #include "IOutputStream.h"
 #include "CThread.h"
 #include "CLog.h"
+#include "CStopwatch.h"
 #include <cstring>
 
 //
@@ -29,22 +30,35 @@ CServerProtocol1_0::~CServerProtocol1_0()
 void
 CServerProtocol1_0::run()
 {
-	// handle messages until the client hangs up
+	// handle messages until the client hangs up or stops sending heartbeats
+	CStopwatch heartTimer;
 	for (;;) {
 		CThread::testCancel();
 
 		// wait for a message
 		UInt8 code[4];
-		UInt32 n = getInputStream()->read(code, 4);
+		UInt32 n = getInputStream()->read(code, 4, kHeartRate);
 		CThread::testCancel();
 
-		// verify we got an entire code
+		// check if client hungup
 		if (n == 0) {
 			log((CLOG_NOTE "client \"%s\" disconnected", getClient().c_str()));
-
-			// client hungup
 			return;
 		}
+
+		// check if client has stopped sending heartbeats
+		if (n == (UInt32)-1) {
+			if (heartTimer.getTime() > kHeartDeath) {
+				log((CLOG_NOTE "client \"%s\" is dead", getClient().c_str()));
+				return;
+			}
+			continue;
+		}
+
+		// got a message so reset heartbeat monitor
+		heartTimer.reset();
+
+		// verify we got an entire code
 		if (n != 4) {
 			log((CLOG_ERR "incomplete message from \"%s\": %d bytes", getClient().c_str(), n));
 
@@ -57,6 +71,10 @@ CServerProtocol1_0::run()
 		if (memcmp(code, kMsgDInfo, 4) == 0) {
 			recvInfo();
 		}
+		else if (memcmp(code, kMsgCNoop, 4) == 0) {
+			// discard no-ops
+			continue;
+		}
 		else if (memcmp(code, kMsgCClipboard, 4) == 0) {
 			recvGrabClipboard();
 		}
@@ -83,8 +101,17 @@ CServerProtocol1_0::queryInfo()
 
 	// wait for and verify reply
 	UInt8 code[4];
-	UInt32 n = getInputStream()->read(code, 4);
-	if (n != 4 && memcmp(code, kMsgDInfo, 4) != 0) {
+	for (;;) {
+		UInt32 n = getInputStream()->read(code, 4, -1.0);
+		if (n == 4) {
+			if (memcmp(code, kMsgCNoop, 4) == 0) {
+				// discard heartbeats
+				continue;
+			}
+			if (memcmp(code, kMsgDInfo, 4) == 0) {
+				break;
+			}
+		}
 		throw XBadClient();
 	}
 
diff --git a/server/CSynergyHook.cpp b/server/CSynergyHook.cpp
index 8440013b..262c27a6 100644
--- a/server/CSynergyHook.cpp
+++ b/server/CSynergyHook.cpp
@@ -468,9 +468,13 @@ init(DWORD threadID)
 {
 	assert(g_hinstance != NULL);
 
-	// see if already initialized
+	// see if already initialized.  if it is we'll shut down and
+	// reinitialize.  this allows the hook DLL to be reclaimed by
+	// a new synergyd if the previous one died unexpectedly.
 	if (g_threadID != 0) {
-		return 0;
+		uninstallScreenSaver();
+		uninstall();
+		cleanup();
 	}
 
 	// save thread id.  we'll post messages to this thread's
@@ -624,9 +628,10 @@ uninstall(void)
 		UnhookWindowsHookEx(g_getMessage);
 		g_getMessage = NULL;
 	}
-	g_keyboard   = NULL;
-	g_mouse      = NULL;
-	g_cbt        = NULL;
+	g_keyboard     = NULL;
+	g_mouse        = NULL;
+	g_cbt          = NULL;
+	g_wheelSupport = kWheelNone;
 
 	// show the cursor
 	restoreCursor();
@@ -664,7 +669,7 @@ uninstallScreenSaver(void)
 	assert(g_hinstance != NULL);
 
 	// uninstall hook unless the mouse wheel hook is installed
-	if (g_getMessage != NULL && g_threadID == 0) {
+	if (g_getMessage != NULL && g_wheelSupport == kWheelNone) {
 		UnhookWindowsHookEx(g_getMessage);
 		g_getMessage = NULL;
 	}
diff --git a/synergy/CInputPacketStream.cpp b/synergy/CInputPacketStream.cpp
index c29a6a04..7b1b792c 100644
--- a/synergy/CInputPacketStream.cpp
+++ b/synergy/CInputPacketStream.cpp
@@ -1,5 +1,6 @@
 #include "CInputPacketStream.h"
 #include "CLock.h"
+#include "CStopwatch.h"
 
 //
 // CInputPacketStream
@@ -26,14 +27,21 @@ CInputPacketStream::close()
 }
 
 UInt32
-CInputPacketStream::read(void* buffer, UInt32 n)
+CInputPacketStream::read(void* buffer, UInt32 n, double timeout)
 {
 	CLock lock(&m_mutex);
 
-	// wait for entire message to be read.  return immediately if
-	// stream hungup.
-	if (!waitForFullMessage()) {
+	// wait for entire message to be read.  return if stream
+	// hungup or timeout.
+	switch (waitForFullMessage(timeout)) {
+	case kData:
+		break;
+
+	case kHungup:
 		return 0;
+
+	case kTimedout:
+		return (UInt32)-1;
 	}
 
 	// limit number of bytes to read to the number of bytes left in the
@@ -43,7 +51,7 @@ CInputPacketStream::read(void* buffer, UInt32 n)
 	}
 
 	// now read from our buffer
-	n = m_buffer.readNoLock(buffer, n);
+	n = m_buffer.readNoLock(buffer, n, -1.0);
 	assert(n <= m_size);
 	m_size -= n;
 
@@ -60,48 +68,70 @@ CInputPacketStream::getSize() const
 UInt32
 CInputPacketStream::getSizeNoLock() const
 {
+	CStopwatch timer(true);
 	while (!hasFullMessage() && getStream()->getSize() > 0) {
 		// read more data
-		if (!getMoreMessage()) {
+		if (getMoreMessage(-1.0) != kData) {
 			// stream hungup
-			return false;
+			return 0;
 		}
 	}
 
 	return m_size;
 }
 
-bool
-CInputPacketStream::waitForFullMessage() const
+CInputPacketStream::EResult
+CInputPacketStream::waitForFullMessage(double timeout) const
 {
+	CStopwatch timer(true);
 	while (!hasFullMessage()) {
+		// compute remaining timeout
+		double t = timeout - timer.getTime();
+		if (timeout >= 0.0 && t <= 0.0) {
+			// timeout
+			return kTimedout;
+		}
+
 		// read more data
-		if (!getMoreMessage()) {
+		switch (getMoreMessage(t)) {
+		case kData:
+			break;
+
+		case kHungup:
 			// stream hungup
-			return false;
+			return kHungup;
+
+		case kTimedout:
+			// stream timed out
+			return kTimedout;
 		}
 	}
 
-	return true;
+	return kData;
 }
 
-bool
-CInputPacketStream::getMoreMessage() const
+CInputPacketStream::EResult
+CInputPacketStream::getMoreMessage(double timeout) const
 {
 	// read more data
 	char buffer[4096];
-	UInt32 n = getStream()->read(buffer, sizeof(buffer));
+	UInt32 n = getStream()->read(buffer, sizeof(buffer), timeout);
+
+	// return if stream timed out
+	if (n == (UInt32)-1) {
+		return kTimedout;
+	}
 
 	// return if stream hungup
 	if (n == 0) {
 		m_buffer.hangup();
-		return false;
+		return kHungup;
 	}
 
 	// append to our buffer
 	m_buffer.write(buffer, n);
 
-	return true;
+	return kData;
 }
 
 bool
@@ -117,7 +147,7 @@ CInputPacketStream::hasFullMessage() const
 
 		// save payload length
 		UInt8 buffer[4];
-		UInt32 n = m_buffer.readNoLock(buffer, sizeof(buffer));
+		UInt32 n = m_buffer.readNoLock(buffer, sizeof(buffer), -1.0);
 		assert(n == 4);
 		m_size = ((UInt32)buffer[0] << 24) |
 				 ((UInt32)buffer[1] << 16) |
diff --git a/synergy/CInputPacketStream.h b/synergy/CInputPacketStream.h
index 03fd32be..c8b123d1 100644
--- a/synergy/CInputPacketStream.h
+++ b/synergy/CInputPacketStream.h
@@ -16,13 +16,15 @@ public:
 
 	// IInputStream overrides
 	virtual void		close();
-	virtual UInt32		read(void*, UInt32 maxCount);
+	virtual UInt32		read(void*, UInt32 maxCount, double timeout);
 	virtual UInt32		getSize() const;
 
 private:
+	enum EResult { kData, kHungup, kTimedout };
+
 	UInt32				getSizeNoLock() const;
-	bool				waitForFullMessage() const;
-	bool				getMoreMessage() const;
+	EResult				waitForFullMessage(double timeout) const;
+	EResult				getMoreMessage(double timeout) const;
 	bool				hasFullMessage() const;
 
 private:
diff --git a/synergy/CProtocolUtil.cpp b/synergy/CProtocolUtil.cpp
index 1b3102b2..9426a2f6 100644
--- a/synergy/CProtocolUtil.cpp
+++ b/synergy/CProtocolUtil.cpp
@@ -348,7 +348,7 @@ CProtocolUtil::read(IInputStream* stream, void* vbuffer, UInt32 count)
 	UInt8* buffer = reinterpret_cast<UInt8*>(vbuffer);
 	while (count > 0) {
 		// read more
-		UInt32 n = stream->read(buffer, count);
+		UInt32 n = stream->read(buffer, count, -1.0);
 
 		// bail if stream has hungup
 		if (n == 0) {
diff --git a/synergy/ProtocolTypes.h b/synergy/ProtocolTypes.h
index 3d2223e2..872a1d7e 100644
--- a/synergy/ProtocolTypes.h
+++ b/synergy/ProtocolTypes.h
@@ -10,6 +10,12 @@ static const SInt16		kProtocolMinorVersion = 1;
 // contact port number
 static const UInt16		kDefaultPort = 24800;
 
+// time between heartbeats (in seconds)
+static const double		kHeartRate = 2.0;
+
+// time without a heartbeat that we call death
+static const double		kHeartDeath = 3.0 * kHeartRate;
+
 //
 // message codes (trailing NUL is not part of code).  in comments, $n
 // refers to the n'th argument (counting from one).  message codes are
@@ -24,6 +30,9 @@ static const UInt16		kDefaultPort = 24800;
 // command codes
 //
 
+// no operation;  secondary -> primary
+static const char		kMsgCNoop[] 		= "CNOP";
+
 // close connection;  primary -> secondary
 static const char		kMsgCClose[] 		= "CBYE";