Use Postman for async endpoints on the Ledger JSON API

Some of the endpoints on the Ledger JSON API are WebSocket endpoints. For example:

• /v2/state/active-contracts
• /v2/updates/flats
• /v2/updates/trees
• /v2/commands/completions

I know how to call such endpoints with wscat.

How do I call those endpoints with Postman?

Take as an example, this successful wscat call:

wscat --connect ws://localhost:7575/v2/updates/trees \
   --subprotocol 'daml.ws.auth' \
   --subprotocol 'jwt.token.eyJhbG...' \
   --execute '{ "verbose": true, "beginExclusive": "0", "filter": { "filtersByParty" : { "Alice::12207...": { "cumulative": [] } } } }'

1. In Postman, create a WebSocket request.
   

   

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2. Set the URL, using ws: as the protocol:
   

   

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3. Add a Sec-WebSocket-Protocol header with a comma separated list of the “subprotocols.” No braces; no quotes.
   

   

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4. Press the “Connect” button.

5. On the Message tab, “Send” a message.

   Sample message

   {
     "verbose": true,
     "beginExclusive": "0",
     "filter": {
       "filtersByParty": {
         "Alice::12207...": {
           "cumulative": []
         }
       }
     }
   }
   

6. In the Response pane, see the response message.

   Sample response

   

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