Improve robustness

Author: manuelbl

java-does-usb/src/main/java/net/codecrete/usb/windows/WindowsUSBDevice.java

@@ -400,15 +400,15 @@ public synchronized void abortTransfers(USBDirection direction, int endpointNumb
     }
 
     @Override
-    public InputStream openInputStream(int endpointNumber, int bufferSize) {
+    public synchronized InputStream openInputStream(int endpointNumber, int bufferSize) {
         // check that endpoint number is valid
         getEndpoint(USBDirection.IN, endpointNumber, USBTransferType.BULK, null);
 
         return new WindowsEndpointInputStream(this, endpointNumber, bufferSize);
     }
 
     @Override
-    public OutputStream openOutputStream(int endpointNumber, int bufferSize) {
+    public synchronized OutputStream openOutputStream(int endpointNumber, int bufferSize) {
         // check that endpoint number is valid
         getEndpoint(USBDirection.OUT, endpointNumber, USBTransferType.BULK, null);