sockets - Autobahn Python Errno 99 cannot assign requested address -

while trying set websocket server, have encountered following error. same code works fine under lan ip '192.168.x.x', fails work public ip/domain name

here error trace

traceback (most recent call last):   file "wsserver.py", line 19, in <module>     server = loop.run_until_complete(coro)   file "/usr/lib64/python3.4/asyncio/base_events.py", line 208, in run_until_complete     return future.result()   file "/usr/lib64/python3.4/asyncio/futures.py", line 243, in result     raise self._exception   file "/usr/lib64/python3.4/asyncio/tasks.py", line 319, in _step     result = coro.send(value)   file "/usr/lib64/python3.4/asyncio/base_events.py", line 579, in create_server     % (sa, err.strerror.lower())) oserror: [errno 99] error while attempting bind on address ('121.6.x.x', 9000): cannot assign requested address 

python server code:

from autobahn.asyncio.websocket import websocketserverprotocol  class myserverprotocol(websocketserverprotocol):     def onmessage(self, payload, isbinary):         print("message received")         self.sendmessage(payload, isbinary)  if __name__ == '__main__':      import asyncio     autobahn.asyncio.websocket import websocketserverfactory     factory = websocketserverfactory()     factory.protocol = myserverprotocol     loop = asyncio.get_event_loop()     coro = loop.create_server(factory, '121.6.x.x', 9000)     server = loop.run_until_complete(coro)      try:         loop.run_forever()     except keyboardinterrupt:         pass     finally:         server.close()         loop.close() 

could issue related server setting? e.g. hostname, selinux