diff --git a/secop/client/__init__.py b/secop/client/__init__.py
index fa73c53..82b1c04 100644
--- a/secop/client/__init__.py
+++ b/secop/client/__init__.py
@@ -30,10 +30,11 @@ from collections import defaultdict
 
 from secop.lib import mkthread, formatExtendedTraceback, formatExtendedStack
 from secop.lib.asynconn import AsynConn, ConnectionClosed
-from secop.datatypes import get_datatype, EnumType
+from secop.datatypes import get_datatype
 from secop.protocol.interface import encode_msg_frame, decode_msg
 from secop.protocol.messages import REQUEST2REPLY, ERRORPREFIX, EVENTREPLY, WRITEREQUEST, WRITEREPLY, \
-    READREQUEST, READREPLY, IDENTREQUEST, IDENTPREFIX, ENABLEEVENTSREQUEST, COMMANDREQUEST, DESCRIPTIONREQUEST
+    READREQUEST, READREPLY, IDENTREQUEST, IDENTPREFIX, ENABLEEVENTSREQUEST, COMMANDREQUEST, \
+    DESCRIPTIONREQUEST, HEARTBEATREQUEST
 import secop.errors
 import secop.params
 
@@ -290,13 +291,19 @@ class SecopClient(ProxyClient):
         self.disconnect(False)
 
     def __rxthread(self):
+        noactivity = 0
         while self._running:
             try:
                 reply = self.io.readline()
                 if reply is None:
+                    noactivity += 1
+                    if noactivity % 5 == 0:
+                        # send ping to check if the connection is still alive
+                        self.queue_request(HEARTBEATREQUEST, str(noactivity))
                     continue
             except ConnectionClosed:
                 break
+            noactivity = 0
             action, ident, data = decode_msg(reply)
             if ident == '.':
                 ident = None
diff --git a/secop/lib/asynconn.py b/secop/lib/asynconn.py
index b874b31..3c45718 100644
--- a/secop/lib/asynconn.py
+++ b/secop/lib/asynconn.py
@@ -159,14 +159,20 @@ class AsynTcp(AsynConn):
         return b''.join(data)
 
     def recv(self):
-        """return bytes received within 1 sec"""
+        """return bytes in the recv buffer
+
+        or bytes received within 1 sec
+        """
         try:
             data = self.connection.recv(8192)
             if data:
                 return data
-        except socket.timeout:
+        except (socket.timeout, TimeoutError):
             # timeout while waiting
             return b''
+        # note that when no data is sent on a connection, an interruption might
+        # not be detected within a reasonable time. sending a heartbeat should
+        # help in this case.
         raise ConnectionClosed()  # marks end of connection
 
 
diff --git a/secop/protocol/interface/tcp.py b/secop/protocol/interface/tcp.py
index 3f1a3fa..d4f6267 100644
--- a/secop/protocol/interface/tcp.py
+++ b/secop/protocol/interface/tcp.py
@@ -145,7 +145,7 @@ class TCPRequestHandler(socketserver.BaseRequestHandler):
                                                                   'traceback': formatExtendedStack()}])
                     except Exception as err:
                         # create Error Obj instead
-                        result = (ERRORPREFIX + msg[0], msg[1], ['InternalError', str(err),
+                        result = (ERRORPREFIX + msg[0], msg[1], ['InternalError', repr(err),
                                                                  {'exception': formatException(),
                                                                   'traceback': formatExtendedStack()}])
                         print('--------------------')
diff --git a/secop/server.py b/secop/server.py
index 47384ed..4dae2f3 100644
--- a/secop/server.py
+++ b/secop/server.py
@@ -100,8 +100,8 @@ class Server:
             cfgdict = self.loadCfgFile(filename)
             ambiguous_sections |= set(merged_cfg) & set(cfgdict)
             merged_cfg.update(cfgdict)
-        self.node_cfg = merged_cfg.pop('NODE')
-        self.interface_cfg = merged_cfg.pop('INTERFACE')
+        self.node_cfg = merged_cfg.pop('NODE', {})
+        self.interface_cfg = merged_cfg.pop('INTERFACE', {})
         self.module_cfg = merged_cfg
         if interface:
             ambiguous_sections.discard('interface')
@@ -109,6 +109,8 @@ class Server:
             self.node_cfg['name'] = name
             self.node_cfg['id'] = cfgfiles
             self.interface_cfg['uri'] = str(interface)
+        elif 'uri' not in self.interface_cfg:
+            raise ConfigError('missing interface uri')
         if ambiguous_sections:
             self.log.warning('ambiguous sections in %s: %r' % (cfgfiles, tuple(ambiguous_sections)))
         self._cfgfiles = cfgfiles
diff --git a/secop/stringio.py b/secop/stringio.py
index cb6bd9f..00d845c 100644
--- a/secop/stringio.py
+++ b/secop/stringio.py
@@ -208,7 +208,7 @@ class HasIodev(Module):
             opts = {'uri': self.uri, 'description': 'communication device for %s' % name,
                     'export': False}
             ioname = name + '_iodev'
-            iodev = self.iodevClass(ioname, self.log.getChild(ioname), opts, srv)
+            iodev = self.iodevClass(ioname, srv.log.getChild(ioname), opts, srv)
             srv.modules[ioname] = iodev
             self.setProperty('iodev', ioname)