code: protected void sendInstruction(GuacamoleInstruction instruction) {
  
          // Temporarily acquire writer to send "ack" instruction
          GuacamoleWriter writer = tunnel.acquireWriter();
  
          // Send successful "ack"
          try {
              writer.writeInstruction(instruction);
          }
          catch (GuacamoleException e) {
              logger.debug("Unable to send \"{}\" for intercepted stream.",
                      instruction.getOpcode(), e);
          }
  
          // Done writing
          tunnel.releaseWriter();
  
      }
docs: Injects an arbitrary Guacamole instruction into the outbound Guacamole
  protocol stream (GuacamoleWriter) of the tunnel associated with this
  StreamInterceptingFilter, as if the instruction was sent by the connected
  client.
  
  @param instruction
  The Guacamole instruction to inject.