Can't publish port again

[MzoroHaHa]

I'm using swarm . I have 3 node. one manager,two worker . I start a service ,and publish a port like this :--publish 20000:20000. The first time everything is ok. but when I delete this service ,then start this service use the same command , I can't attach the app in this service throgh 20000 port:

docker service create --network name=barn-stack_barn-network,alias=eureka --publish published=20000,target=20000 --replicas=2 zoro/eureka

root@zoro:~/files/workspace/swarm/stack# docker network ls
NETWORK ID     NAME                      DRIVER    SCOPE
rcpsmacuy0hw   barn-stack_barn-network   overlay   swarm
.....

I can confirm , no other program use the same port.

what should I do?

thanks.