sorry for not replying. i switched to Autobahn|Python.
there i just have to this:
```python
class CancallableProtocol(WebSocketServerProtocol):
task = None
def onMessage(self, payload, isBinary):
if data == 'cancel' and self.task:
if self.task.done():
print('already done', self.task.result())
else:
print('cancelling')
self.task.set_result('{"cancelled": true}')
self.task = None
elif not self.task:
self.task = asyncio.async(self.do_task(payload))
result = yield from self.task
self.sendMessage(result)
else:
print('multiple tasks not yet implemented')
def do_task(self, data):
...
```
a shame about the camelCase, though :)
