Added GuacamoleReader.available(), using to determine appropriate times to flush tunnel servlet output.

guacamole-common/src/main/java/net/sourceforge/guacamole/io/GuacamoleReader.java

@@ -48,6 +48,19 @@ import net.sourceforge.guacamole.protocol.GuacamoleInstruction;
  */
 public interface GuacamoleReader {
 
+    /**
+     * Returns whether instruction data is available for reading. Note that
+     * this does not guarantee an entire instruction is available. If a full
+     * instruction is not available, this function can return true, and a call
+     * to read() will still block.
+     * 
+     * @return true if instruction data is available for reading, false
+     *         otherwise.
+     * @throws GuacamoleException If an error occurs while checking for
+     *                            available data.
+     */
+    public boolean available() throws GuacamoleException;
+    
     /**
      * Reads at least one complete Guacamole instruction, returning a buffer
      * containing one or more complete Guacamole instructions and no

guacamole-common/src/main/java/net/sourceforge/guacamole/io/ReaderGuacamoleReader.java

@@ -70,6 +70,16 @@ public class ReaderGuacamoleReader implements GuacamoleReader {
     private char[] buffer = new char[20480];
     private int usedLength = 0;
 
+    @Override
+    public boolean available() throws GuacamoleException {
+        try {
+            return input.ready() || usedLength != 0;
+        }
+        catch (IOException e) {
+            throw new GuacamoleException(e);
+        }
+    }
+
     @Override
     public char[] read() throws GuacamoleException {
 

guacamole-common/src/main/java/net/sourceforge/guacamole/servlet/GuacamoleTunnelServlet.java

@@ -224,8 +224,12 @@ public abstract class GuacamoleTunnelServlet extends HttpServlet {
 
                 // Get message output bytes
                 out.write(message, 0, message.length);
+
+                // Flush if we expect to wait
+                if (!reader.available()) {
                     out.flush();
                     response.flushBuffer();
+                }
 
                 // No more messages another stream can take over
                 if (tunnel.hasQueuedReaderThreads())