# System subjects

This page describes Liberator system subjects that StreamLink clients can subscribe to.

## /SYSTEM/NOTIFY/STATE

The operational state of the Liberator. StreamLink clients can subscribe to this subject to be alerted when a graceful shutdown is initiated on the Liberator they are connected to. This gives the clients an opportunity to transfer their connection to another Liberator.

The subject has three fields: `state`, `info`, and `message`. 

**Normal operation**

| Field | Value |
| --- | --- |
| state | "Operational" |
| info |  |
| message |  |

**Graceful shutdown scheduled (from Liberator 7.1.5)**

| Field | Value |
| --- | --- |
| state | "Shutdown scheduled" |
| info | The date and time when the grace-period starts. Format: `yyyy-mm-ddThh:mm:ss` |
| message | A message, set by the system administrator, describing the reason for the graceful shutdown. |

**Graceful shutdown initiated**

| Field | Value |
| --- | --- |
| state | "Shutting down" |
| info | The date and time when the grace-period ends. Format: `yyyy-mm-ddThh:mm:ss` |
| message | A message, set by the system administrator, describing the reason for the graceful shutdown. |

For information on how a system administrator can initiate a graceful shutdown, see [Liberator UDP commands](liberator-udp-commands.md).