# SendSdpAnswer
<a name="SendSdpAnswer"></a>

Sends the answer to the target recipient. The prerequisite is that the client must be already connected to the WebSocket endpoint obtained from the `GetSignalingChannelEndpoint` API.

If the sender type is a viewer, then it sends the answer to a master. Also, it is not necessary to specify the `RecipientClientId` and any specified value for `RecipientClientId` is ignored. If the sender type is master, the answer is sent to the target viewer specified by the `RecipientClientId`. `RecipientClientId` is a required input in this case.

A master client app is allowed to send an answer to any viewer, whereas a viewer client app is only allowed to send an answer to a master client app. If a viewer client app attempts to send an answer to another viewer client app, the request will NOT be honored. If there is an outstanding answer for the same client which is not yet delivered, it is overwritten with the new answer.

## Request
<a name="SendSdpAnswer-request"></a>

```
{
    "action": "SDP_ANSWER",
    "recipientClientId": "string",
    "messagePayload": "string",
    "correlationId": "string"
}
```
+ **action** - Type of the message that is being sent.
  + Type: ENUM
  + Valid values: `SDP_OFFER`, `SDP_ANSWER`, `ICE_CANDIDATE`
  + Length constraints: Minimum length of 1. Maximum length of 256.
  + Pattern: `[a-zA-Z0-9_.-]+`
  + Required: Yes
+ **recipientClientId** - The unique identifier for the recipient.
  + Type: String
  + Length constraints: Minimum length of 1. Maximum length of 256.
  + Pattern: `[a-zA-Z0-9_.-]+`
  + Required: Yes
+ **messagePayload** - The base-64-encoded message content.
  + Type: String
  + Length constraints: Minimum length of 1. Maximum length of 10K.
  + Required: Yes
+ **correlationId** - A unique identifier for the message.
  + Type: String
  + Length constraints: Minimum length of 1. Maximum length of 256.
  + Pattern: `[a-zA-Z0-9_.-]+`
  + Required: No

## Response
<a name="SendSdpAnswer-response"></a>

No response is returned if the message is successfully received by the signaling backend. If the service encounters an error and if the `correlationId` is specified in the request, the error details are returned as a `STATUS_RESPONSE` message. For more information, see [Asynchronous message reception](async-message-reception-api.md).

## Errors
<a name="SendSdpAnswer-errors"></a>
+ InvalidArgumentException

  A specified parameter exceeds its restrictions, is not supported, or cannot be used. For more information, see the returned message.

  HTTP Status Code: 400
+ ClientLimitExceededException

  Returned when the API is invoked at a rate that is too high. For more information, see [Amazon Kinesis Video Streams with WebRTC service quotas](kvswebrtc-limits.md) and [Error Retries and Exponential Backoff in AWS](https://docs.aws.amazon.com/general/latest/gr/api-retries.html).

  HTTP Status Code: 400

## Limits/Throttling
<a name="SendSdpAnswer-limits"></a>

This API is throttled at an account level if the API is invoked at too high a rate. An error is returned when throttled with `ClientLimitExceededException`.

## Idempotent
<a name="SendSdpAnswer-idempotent"></a>

This API is not idempotent.

## Retry behavior
<a name="SendSdpAnswer-retry"></a>

This is counted as a new API call.

## Concurrent calls
<a name="SendSdpAnswer-concurrent"></a>

Concurrent calls are allowed. An offer is sent once per each call.