The message SERVER_DISCONNECT_CONCURRENT_CONNECTION means the server sees more than one active session using the same NTRIP credentials. In that case, it will disconnect the previous connection and keep the newest one, so the most recently started client continues to receive corrections.
This can happen when:
- Multiple clients (u-center, RTKLib, receiver’s internal NTRIP client, etc.) use the same username/password at the same time.
- A service (like systemd) restarts the NTRIP client quickly, causing a short overlap where the old connection hasn’t fully closed yet.
If this message appears occasionally, it can usually be ignored: the latest connection will take priority and continue receiving corrections.
If you see many repeated SERVER_DISCONNECT_CONCURRENT_CONNECTION events, this could point to a more serious issue (e.g. unstable client, misconfigured service, or multiple parallel clients), and the system stability/setup should be checked.