Use @connections commands in your backend service - Amazon API Gateway

Use @connections commands in your backend service

Your backend service can use the following WebSocket connection HTTP requests to send a callback message to a connected client, get connection information, or disconnect the client.


These requests use IAM authorization, so you must sign them with Signature Version 4 (SigV4). To do this, you can use the API Gateway Management API. For more information, see ApiGatewayManagementApi.

In the following command, you need to replace {api-id} with the actual API ID, which is displayed in the API Gateway console or returned by the AWS CLI create-api command. You must establish the connection before using this command.

To send a callback message to the client, use:

POST https://{api-id}{stage}/@connections/{connection_id}

You can test this request by using Postman or by calling awscurl as in the following example:

awscurl --service execute-api -X POST -d "hello world" https://{prefix}{stage}/@connections/{connection_id}

You need to URL-encode the command as in the following example:

awscurl --service execute-api -X POST -d "hello world"

To get the latest connection status of the client, use:

GET https://{api-id}{stage}/@connections/{connection_id}

To disconnect the client, use:

DELETE https://{api-id}{stage}/@connections/{connection_id}

You can dynamically build a callback URL by using the $context variables in your integration. For example, if you use Lambda proxy integration with a Node.js Lambda function, you can build the URL and send a message to a connected client as follows:

import { ApiGatewayManagementApiClient, PostToConnectionCommand, } from "@aws-sdk/client-apigatewaymanagementapi"; export const handler = async (event) => { const domain = event.requestContext.domainName; const stage = event.requestContext.stage; const connectionId = event.requestContext.connectionId; const callbackUrl = `https://${domain}/${stage}`; const client = new ApiGatewayManagementApiClient({ endpoint: callbackUrl }); const requestParams = { ConnectionId: connectionId, Data: "Hello!", }; const command = new PostToConnectionCommand(requestParams); try { await client.send(command); } catch (error) { console.log(error); } return { statusCode: 200, }; };

When sending a callback message, your Lambda function must have permission to call the API Gateway Management API. You might receive an error that contains GoneException if you post a message before the connection is established, or after the client has disconnected.