Flush data on close

There might be some final handshake data that is still stuck in the
buffers, so make a best effort attempt at getting it to the client.

common/rfb/VNCSConnectionST.cxx

@@ -155,6 +155,17 @@ void VNCSConnectionST::close(const char* reason)
       server->lastDisconnectTime = time(0);
   }
 
+  try {
+    if (sock->outStream().bufferUsage() > 0) {
+      sock->cork(false);
+      sock->outStream().flush();
+      if (sock->outStream().bufferUsage() > 0)
+        vlog.error("Failed to flush remaining socket data on close");
+    }
+  } catch (rdr::Exception& e) {
+    vlog.error("Failed to flush remaining socket data on close: %s", e.str());
+  }
+
   // Just shutdown the socket and mark our state as closing.  Eventually the
   // calling code will call VNCServerST's removeSocket() method causing us to
   // be deleted.