I managed to reproduce the problem you saw with gtk-vnc and windows
hanging. With the glib IO debug turned up high I can see it is treating
the FD as a file handle, rather than a socket - which is to be expected
because gnulib is wrapping winsock to give back real FDs.

Unfortunately glib is on crack, and for file handles it implements
IO waits by having a background thread for each file handle that sits
in a read/write call forever, and sets flags. To quote the docs

  "If you have created a GIOChannel for a file descriptor and started 
   watching (polling) it, you shouldn't call read() on the file descriptor.
   This is because adding polling for a file descriptor is implemented in 
   GLib on Windows by starting a thread that sits blocked in a read() from
   the file descriptor most of the time. All reads from the file descriptor 
   should be done by this internal GLib thread. Your code should call only 
   g_io_channel_read(). "

This is just epic fail when combined with what we want todo. Making gtk-vnc
use g_io_channel_read() instead didn't work either. I think the glib thread
concept simply doesn't work for FDs which are aliases for sockets.

So I've tried a atch which creates an IO channel using 

  g_io_channel_win32_new_socket(_get_osfhandle(fd))

to explicitly make glib treat it as a socket, and avoid the thread insanity.
Slightly nasty because we're reversing gnulibs magic by translating the
FD back into a socket, but empirically it seems to work better for me. I've
not yet got it  to hang with this patch.

I also needed to make our read/write functions use the 'fd' in the gvnc
struct, instead of fetching it from the IOChannel object.

Let me know if this patch works for you too....

Daniel

diff --git a/src/gvnc.c b/src/gvnc.c
--- a/src/gvnc.c
+++ b/src/gvnc.c
@@ -347,7 +347,6 @@ static int gvnc_zread(struct gvnc *gvnc,
 
 static int gvnc_read(struct gvnc *gvnc, void *data, size_t len)
 {
-	int fd = g_io_channel_unix_get_fd(gvnc->channel);
 	char *ptr = data;
 	size_t offset = 0;
 
@@ -380,7 +379,7 @@ static int gvnc_read(struct gvnc *gvnc, 
 					ret = -1;
 				}
 			} else
-				ret = recv (fd, gvnc->read_buffer, 4096, 0);
+				ret = recv (gvnc->fd, gvnc->read_buffer, 4096, 0);
 
 			if (ret == -1) {
 				switch (errno) {
@@ -422,7 +421,6 @@ static int gvnc_read(struct gvnc *gvnc, 
 
 static void gvnc_flush(struct gvnc *gvnc)
 {
-	int fd = g_io_channel_unix_get_fd(gvnc->channel);
 	size_t offset = 0;
 	while (offset < gvnc->write_offset) {
 		int ret;
@@ -439,7 +437,7 @@ static void gvnc_flush(struct gvnc *gvnc
 				ret = -1;
 			}
 		} else
-			ret = send (fd,
+			ret = send (gvnc->fd,
 				    gvnc->write_buffer+offset,
 				    gvnc->write_offset-offset, 0);
 		if (ret == -1) {
@@ -490,11 +488,10 @@ static ssize_t gvnc_tls_push(gnutls_tran
 			      const void *data,
 			      size_t len) {
 	struct gvnc *gvnc = (struct gvnc *)transport;
-	int fd = g_io_channel_unix_get_fd(gvnc->channel);
 	int ret;
 
  retry:
-	ret = write(fd, data, len);
+	ret = write(gvnc->fd, data, len);
 	if (ret < 0) {
 		if (errno == EINTR)
 			goto retry;
@@ -508,11 +505,10 @@ static ssize_t gvnc_tls_pull(gnutls_tran
 			     void *data,
 			     size_t len) {
 	struct gvnc *gvnc = (struct gvnc *)transport;
-	int fd = g_io_channel_unix_get_fd(gvnc->channel);
 	int ret;
 
  retry:
-	ret = read(fd, data, len);
+	ret = read(gvnc->fd, data, len);
 	if (ret < 0) {
 		if (errno == EINTR)
 			goto retry;
@@ -2872,7 +2868,13 @@ gboolean gvnc_open_fd(struct gvnc *gvnc,
 	if (!gvnc_set_nonblock(fd))
 		return FALSE;
 
-	if (!(gvnc->channel = g_io_channel_unix_new(fd))) {
+	if (!(gvnc->channel =
+#ifdef WIN32
+	      g_io_channel_win32_new_socket(_get_osfhandle(fd))
+#else
+	      g_io_channel_unix_new(fd)
+#endif
+	      )) {
 		GVNC_DEBUG ("Failed to g_io_channel_unix_new()\n");
 		return FALSE;
 	}
@@ -2917,7 +2919,13 @@ gboolean gvnc_open_host(struct gvnc *gvn
 		if (!gvnc_set_nonblock(fd))
 			break;
 
-                if (!(chan = g_io_channel_unix_new(fd))) {
+                if (!(chan =
+#ifdef WIN32
+		      g_io_channel_win32_new_socket(_get_osfhandle(fd))
+#else
+		      g_io_channel_unix_new(fd)
+#endif
+		      )) {
                         close(fd);
                         GVNC_DEBUG ("Failed to g_io_channel_unix_new()\n");
                         break;

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