synergy hook DLL will now restart itself if a client tries to

init() it while it's already running.  fixed an uninitialized
pointer bug in CServer and some cleanup-on-error code in
CMSWindowsPrimaryScreen.  also added timeout to read() on
IInputStream and a heartbeat sent by clients so the server
can disconnect clients that are dead but never reset the TCP
connection.  previously the server would keep these dead
clients around forever and if the user was locked on the
client screen for some reason then the server would have to
be rebooted (or the server would have to be killed via a
remote login).

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();
 			}

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) {

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

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:

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:

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.
+	// then the data is discarded.  returns (UInt32)-1 if there's
-	virtual UInt32		read(void* buffer, UInt32 maxCount) = 0;
+	// 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
 

server/CMSWindowsPrimaryScreen.cpp

@@ -386,6 +386,7 @@ CMSWindowsPrimaryScreen::onOpenDisplay()
 	// initialize hook library
 	m_init(m_threadID);
 
+	try {
 		// install the screen saver hook
 		if (m_installScreenSaver != NULL) {
 			m_installScreenSaver();
@@ -403,6 +404,11 @@ CMSWindowsPrimaryScreen::onOpenDisplay()
 			}
 		}
 	}
+	catch (...) {
+		m_cleanup();
+		throw;
+	}
+}
 
 void
 CMSWindowsPrimaryScreen::onCloseDisplay()

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)
 {

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);
+	for (;;) {
-	if (n != 4 && memcmp(code, kMsgDInfo, 4) != 0) {
+		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();
 	}
 

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
@@ -627,6 +631,7 @@ uninstall(void)
 	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;
 	}

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
+	// wait for entire message to be read.  return if stream
-	// stream hungup.
+	// hungup or timeout.
-	if (!waitForFullMessage()) {
+	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::EResult
-CInputPacketStream::waitForFullMessage() const
+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::EResult
-CInputPacketStream::getMoreMessage() const
+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) |

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;
+	EResult				waitForFullMessage(double timeout) const;
-	bool				getMoreMessage() const;
+	EResult				getMoreMessage(double timeout) const;
 	bool				hasFullMessage() const;
 
 private:

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) {

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";