Can't get real-time subscription from rpc pubsub client.

[endlesspennier]

Problem

I have installed agave solana rpc node at my ubuntu server. Here is my command:

exec /root/agave/target/release/agave-validator
--identity /root/validator/validator-keypair.json
--vote-account /root/validator/vote-account-keypair.json
--known-validator 7Np41oeYqPefeNQEHSv1UDhYrehxin3NStELsSKCT4K2
--known-validator GdnSyH3YtwcxFvQrVVJMm1JhTS4QVX7MFsX56uJLUfiZ
--known-validator DE1bawNcRJB9rVm3buyMVfr8mBEoyyu73NBovf2oXJsJ
--known-validator CakcnaRDHka2gXyfbEd2d3xsvkJkqsLw2akB3zsN1D2S
--full-rpc-api
--only-known-rpc
--no-voting
--ledger /mnt/ledger
--rpc-bind-address 0.0.0.0
--rpc-port 8899
--rpc-threads 24
--rpc-pubsub-notification-threads 4
--private-rpc
--dynamic-port-range 8000-8020
--entrypoint entrypoint.mainnet-beta.solana.com:8001
--entrypoint entrypoint2.mainnet-beta.solana.com:8001
--entrypoint entrypoint3.mainnet-beta.solana.com:8001
--entrypoint entrypoint4.mainnet-beta.solana.com:8001
--entrypoint entrypoint5.mainnet-beta.solana.com:8001
--expected-genesis-hash 5eykt4UsFv8P8NJdTREpY1vzqKqZKvdpKuc147dw2N9d
--wal-recovery-mode skip_any_corrupted_record
--limit-ledger-size
--accounts /mnt/accounts
--health-check-slot-distance 2
--disable-banking-trace

After run, I can make rpc request and get response from 8899 port. But I can not subscribe using 8900 port at the same time.
I can connect websocket server, but I can not get any real time data from that.
I did use logsSubscribe.

I appreciate it if anyone knows the solution to resolve this issue.