PUT Requests

PUT requests are sent to a server to request a change to a value. For example, a client would use PUT to switch the anchor light on or off, change the heading of the autopilot, or set position of the anchor.

See Request/Response for more details on request/response in Signal K.

Making a Request to Change a Value

To change a value, a PUT request should be sent via HTTP or using a Signal K put delta.

The source field is optional. If a request is sent without the source and there is more than one source for the value, the server should respond with a 400 (Bad Request) HTTP status code.

Via HTTP

PUT http://localhost:3000/signalk/v1/api/vessels/self/steering/autopilot/target/headingTrue
{
  "value": 1.52,
  "source": "actisense.204",
}

Via a Delta

```
[<]: #

The `context` key is optional, and defaults to `vessels.self`, which is the usual case. You can include it to be able to set values on other vessels.

#### NOTE ####
The above PUT request (v1) uses an array to allow multiple keys in a single PUT. This is deprecated and strongly discouraged as it causes complex problems 
with the request/response semantics in cases of partial failures.  An alternative format has been added to the v1 specification where the  PUT request is:

[>]: # (mdpInsert ```json fsnip ../data/put-valid/delta-put-no-array.json)
```json

In the v2 API the array format will be removed. Implementors are recommended to support both in the interim.

Return states

A PUT request in the array format is only successful if ALL if the items are successful. It is up to the client to ascertain which were in error, and why.