--- a/ProjectController.py	Fri Feb 01 14:14:13 2019 +0100
+++ b/ProjectController.py	Wed Feb 13 09:41:35 2019 +0100
@@ -1873,11 +1873,14 @@
                 extrafiles.append((
                     name, 
                     self._connector.BlobFromFile(
-                        os.path.join(extrafilespath, name))))
+                        # use file name as a seed to avoid collisions
+                        # with files having same content
+                        os.path.join(extrafilespath, name),name)))
 
         # Send PLC on target
         object_path = builder.GetBinaryPath()
-        object_blob = self._connector.BlobFromFile(object_path)
+        # arbitrarily use MD5 as a seed, could be any string
+        object_blob = self._connector.BlobFromFile(object_path, MD5)
 
         self.HidePLCProgress()
 

--- a/connectors/ConnectorBase.py	Fri Feb 01 14:14:13 2019 +0100
+++ b/connectors/ConnectorBase.py	Wed Feb 13 09:41:35 2019 +0100
@@ -9,14 +9,14 @@
 
     #chuncksize = 16384
     chuncksize = 1024*1024
-    def BlobFromFile(self, filepath): 
+    def BlobFromFile(self, filepath, seed):
         s = md5.new()
-        blobID = s.digest()  # empty md5, to support empty blob
+        s.update(seed)
+        blobID = self.SeedBlob(seed)
         with open(filepath, "rb") as f:
-            while True:
+            while blobID == s.digest():
                 chunk = f.read(self.chuncksize) 
                 if len(chunk) == 0: return blobID
                 blobID = self.AppendChunkToBlob(chunk, blobID)
                 s.update(chunk)
-                if blobID != s.digest(): return None
 

--- a/runtime/PLCObject.py	Fri Feb 01 14:14:13 2019 +0100
+++ b/runtime/PLCObject.py	Wed Feb 13 09:41:35 2019 +0100
@@ -45,8 +45,6 @@
 from runtime import PlcStatus
 from runtime import MainWorker
 
-empty_md5_digest = md5.new().digest()
-
 if os.name in ("nt", "ce"):
     dlopen = _ctypes.LoadLibrary
     dlclose = _ctypes.FreeLibrary
@@ -468,11 +466,17 @@
         os.mkdir(self.tmpdir)
     
     @RunInMain
+    def SeedBlob(self, seed):
+        blob = (mkstemp(dir=self.tmpdir) + (md5.new(),))
+        fobj, path, md5sum = blob
+        md5sum.update(seed)
+        newBlobID = md5sum.digest()
+        self.blobs[newBlobID] = blob
+        return newBlobID
+
+    @RunInMain
     def AppendChunkToBlob(self, data, blobID):
-        blob = ((mkstemp(dir=self.tmpdir) if data else None)\
-                   + (md5.new(),)) \
-               if blobID == empty_md5_digest \
-               else self.blobs.pop(blobID, None)
+        blob = self.blobs.pop(blobID, None)
 
         if blob is None:
             return None
@@ -480,9 +484,8 @@
         fobj, path, md5sum = blob
         md5sum.update(data)
         newBlobID = md5sum.digest()
-        if data:
-            os.write(fobj,data)
-            self.blobs[newBlobID] = blob
+        os.write(fobj,data)
+        self.blobs[newBlobID] = blob
         return newBlobID
 
     @RunInMain
@@ -495,10 +498,6 @@
         blob = self.blobs.pop(blobID, None)
 
         if blob is None:
-            if blobID == md5.new().digest():
-                # create empty file
-                open(newpath,'r').close()
-                return
             raise Exception(_("Missing data to create file: {}").format(newpath))
 
         fobj, path, md5sum = blob

--- a/runtime/WampClient.py	Fri Feb 01 14:14:13 2019 +0100
+++ b/runtime/WampClient.py	Wed Feb 13 09:41:35 2019 +0100
@@ -57,6 +57,7 @@
     ("StopPLC", {}),
     ("GetPLCstatus", {}),
     ("GetPLCID", {}),
+    ("SeedBlob", {}),
     ("AppendChunkToBlob", {}),
     ("PurgeBlobs", {}),
     ("NewPLC", {}),