diff --git a/bitkeylib/client.py b/bitkeylib/client.py
index 9463468b58..81ed98941c 100644
--- a/bitkeylib/client.py
+++ b/bitkeylib/client.py
@@ -64,28 +64,34 @@ class BitkeyClient(object):
             print '----------------------'
             print "Sending", self._pprint(msg)
         
-        self.transport.write(msg)
-        resp = self.transport.read_blocking()
-
-        if isinstance(resp, proto.ButtonRequest):
-            if self.debuglink and self.debug_button:
-                print "Pressing button", self.debug_button
-                self.debuglink.press_button(self.debug_button)
-            
-            return self.call(proto.ButtonAck())   
-                   
-        if isinstance(resp, proto.PinMatrixRequest):
-            if self.debuglink:
-                if self.debug_pin:
-                    pin = self.debuglink.read_pin_encoded()
-                    msg2 = proto.PinMatrixAck(pin=pin)
-                else:
-                    msg2 = proto.PinMatrixAck(pin='444444222222')
-            else:
-                pin = self.input_func("PIN required: ", resp.message)
-                msg2 = proto.PinMatrixAck(pin=pin)
+        try:
+            self.transport.session_begin()
+                    
+            self.transport.write(msg)
+            resp = self.transport.read_blocking()
+    
+            if isinstance(resp, proto.ButtonRequest):
+                if self.debuglink and self.debug_button:
+                    print "Pressing button", self.debug_button
+                    self.debuglink.press_button(self.debug_button)
                 
-            return self.call(msg2)
+                return self.call(proto.ButtonAck())   
+                       
+            if isinstance(resp, proto.PinMatrixRequest):
+                if self.debuglink:
+                    if self.debug_pin:
+                        pin = self.debuglink.read_pin_encoded()
+                        msg2 = proto.PinMatrixAck(pin=pin)
+                    else:
+                        msg2 = proto.PinMatrixAck(pin='444444222222')
+                else:
+                    pin = self.input_func("PIN required: ", resp.message)
+                    msg2 = proto.PinMatrixAck(pin=pin)
+                    
+                return self.call(msg2)
+
+        finally:
+            self.transport.session_end()
         
         if isinstance(resp, proto.Failure):
             self.message_func(resp.message)
@@ -132,49 +138,55 @@ class BitkeyClient(object):
     
         start = time.time()
         
-        # Prepare and send initial message
-        tx = proto.SignTx()
-        tx.inputs_count = len(inputs)
-        tx.outputs_count = len(outputs)            
-        res = self.call(tx)
-
-        # Prepare structure for signatures
-        signatures = [None]*len(inputs)
-        serialized_tx = ''
-        
-        counter = 0
-        while True:
-            counter += 1
+        try:    
+            self.transport.session_begin()
             
-            if isinstance(res, proto.Failure):
-                raise CallException("Signing failed")
-
-            if not isinstance(res, proto.TxRequest):
-                raise CallException("Unexpected message")
-
-            # If there's some part of signed transaction, let's add it
-            if res.serialized_tx:
-                print "!!! RECEIVED PART OF SERIALIED TX (%d BYTES)" % len(res.serialized_tx)
-                serialized_tx += res.serialized_tx
-
-            if res.signed_index >= 0 and res.signature:
-                print "!!! SIGNED INPUT", res.signed_index
-                signatures[res.signed_index] = res.signature
+            # Prepare and send initial message
+            tx = proto.SignTx()
+            tx.inputs_count = len(inputs)
+            tx.outputs_count = len(outputs)            
+            res = self.call(tx)
+    
+            # Prepare structure for signatures
+            signatures = [None]*len(inputs)
+            serialized_tx = ''
+                         
+            counter = 0
+            while True:
+                counter += 1
                 
-            if res.request_index < 0:
-                # Device didn't ask for more information, finish workflow
-                break
-            
-            # Device asked for one more information, let's process it.
-            if res.request_type == proto.TXOUTPUT:
-                res = self.call(outputs[res.request_index])
-                continue
-          
-            elif res.request_type == proto.TXINPUT:
-                print "REQUESTING", res.request_index    
-                res = self.call(inputs[res.request_index])
-                continue                
-        
+                if isinstance(res, proto.Failure):
+                    raise CallException("Signing failed")
+    
+                if not isinstance(res, proto.TxRequest):
+                    raise CallException("Unexpected message")
+    
+                # If there's some part of signed transaction, let's add it
+                if res.serialized_tx:
+                    print "!!! RECEIVED PART OF SERIALIED TX (%d BYTES)" % len(res.serialized_tx)
+                    serialized_tx += res.serialized_tx
+    
+                if res.signed_index >= 0 and res.signature:
+                    print "!!! SIGNED INPUT", res.signed_index
+                    signatures[res.signed_index] = res.signature
+                    
+                if res.request_index < 0:
+                    # Device didn't ask for more information, finish workflow
+                    break
+                
+                # Device asked for one more information, let's process it.
+                if res.request_type == proto.TXOUTPUT:
+                    res = self.call(outputs[res.request_index])
+                    continue
+              
+                elif res.request_type == proto.TXINPUT:
+                    print "REQUESTING", res.request_index    
+                    res = self.call(inputs[res.request_index])
+                    continue                
+
+        finally:
+            self.transport.session_end()
+                    
         print "SIGNED IN %.03f SECONDS, CALLED %d MESSAGES, %d BYTES" % \
                 (time.time() - start, counter, len(serialized_tx))
                 
diff --git a/bitkeylib/transport.py b/bitkeylib/transport.py
index ad13c3f628..c7e8060746 100644
--- a/bitkeylib/transport.py
+++ b/bitkeylib/transport.py
@@ -7,6 +7,7 @@ class NotImplementedException(Exception):
 class Transport(object):
     def __init__(self, device, *args, **kwargs):
         self.device = device
+        self.session_depth = 0
         self._open()
     
     def _open(self):
@@ -21,8 +22,25 @@ class Transport(object):
     def _read(self):
         raise NotImplementedException("Not implemented")
     
+    def _session_begin(self):
+        pass
+    
+    def _session_end(self):
+        pass
+    
     def ready_to_read(self):
         raise NotImplementedException("Not implemented")
+    
+    def session_begin(self):
+        if self.session_depth == 0:
+            self._session_begin()
+        self.session_depth += 1
+    
+    def session_end(self):
+        self.session_depth -= 1
+        self.session_depth = max(0, self.session_depth)
+        if self.session_depth == 0:
+            self._session_end()
         
     def close(self):
         self._close()