Improve exception handling

- there were reports of errors in FreeBSD (I could only reproduce some)
  and Gentoo without IPv4 support (I don't have a VM for testing ready)
- adds an exception handler for double task_done in case sender thread
  has to close prematurely (I saw this triggered on FreeBSD 11)
- listening socket opening error handler was broken (triggered if you
  can't open a socket with both IPv4 and IPv6 support)
- error handler for socket.accept. Reported on FreeBSD 10.3
- fixes #854

src/class_sendDataThread.py

@@ -201,7 +201,11 @@ class sendDataThread(threading.Thread):
             elif self.connectionIsOrWasFullyEstablished:
                 logger.error('sendDataThread ID: ' + str(id(self)) + ' ignoring command ' + command + ' because the thread is not in stream ' + str(deststream) + ' but in streams ' + ', '.join(str(x) for x in self.streamNumber))
             self.sendDataThreadQueue.task_done()
-        self.sendDataThreadQueue.task_done()
+        # Flush if the cycle ended with break
+        try:
+            self.sendDataThreadQueue.task_done()
+        except ValueError
+            pass
 
         try:
             self.sock.shutdown(socket.SHUT_RDWR)

src/class_singleListener.py

@@ -86,7 +86,7 @@ class singleListener(threading.Thread, StoppableThread):
         # we'll fall back to IPv4-only.
         try:
             sock = self._createListenSocket(socket.AF_INET6)
-        except socket.error, e:
+        except socket.error as e:
             if (isinstance(e.args, tuple) and
                 e.args[0] in (errno.EAFNOSUPPORT,
                               errno.EPFNOSUPPORT,
@@ -112,7 +112,15 @@ class singleListener(threading.Thread, StoppableThread):
                 self.stop.wait(10)
 
             while state.shutdown == 0:
-                socketObject, sockaddr = sock.accept()
+                try:
+                    socketObject, sockaddr = sock.accept()
+                except socket.error as e:
+                    if isinstance(e.args, tuple) and
+                        e.args[0] in (errno.EINTR,):
+                        continue
+                    time.wait(1)
+                    continue
+
                 (HOST, PORT) = sockaddr[0:2]
 
                 # If the address is an IPv4-mapped IPv6 address then