C Class Messages
C-Class train describer messages provide updates relating to the stepping of train descriptions between TD berths.
There are four types of C-Class message:
| Type | Name | Details |
|---|---|---|
| CA | Berth Step | The CA message is a 'step' message.
This moves the description from the 'from' berth, in to the 'to' berth, cancelling the description in the 'from' berth and overwriting any description in the 'to' berth. |
| CB | Berth Cancel | The CB message is a 'cancel' message.
This cancels the description in the 'from' berth. |
| CC | Berth Interpose | The CC message is an 'interpose' message.
This inserts the description in to the 'to' berth, overwriting any description in the 'to' berth. |
| CT | Heartbeat | The CT message is a 'heartbeat' message, periodically sent from a train describer. |
Message Format
Messages are sent in JSON format, as follows:
- {"CA_MSG":{"time":"1349696911000", "area_id":"SK", "msg_type":"CA", "from":"3647", "to":"3649", "descr":"1F42"}}
- {"CB_MSG":{"time":"1349696911000", "area_id":"G1", "msg_type":"CB", "from":"G669", "descr":"2J01"}}
- {"CC_MSG":{"time":"1349696911000", "area_id":"G1", "msg_type":"CC", "descr":"2J01", "to":"G669"}}
- {"CT_MSG":{"time":"1349696911000", "area_id":"SA", "msg_type":"CT", "report_time":"1249"}}
Message Fields
| Field | CA | CB | CC | CT | Details |
|---|---|---|---|---|---|
| time | • | • | • | • | Message time
UNIX timestamp in milliseconds since the UNIX epoch |
| area_id | • | • | • | • | Alphanumeric code representing the TD area that the message originates from (see list of train describers) |
| msg_type | • | • | • | • | Type of message
Can be CA_MSG, CB_MSG, CC_MSG or CT_MSG |
| from | • | • | From berth (see TD berths page) | ||
| to | • | • | To berth (see TD berths page) | ||
| descr | • | • | • | Train description
Four-letter alphanumeric code representing the headcode or description of the train | |
| report_time | • | Reporting time |