This repo contains an example under the example folder for listening to Postgresql Logical Replication using the dart postgres package (pub | repo) -- version 2.5.0 or above. This allows listening to changes in PostgreSQL database in the following manner:

• Insert changes (one row):

  {
      "change": [
              {
                  "kind": "insert",
                  "schema": "public",
                  "table": "temp",
                  "columnnames": ["id", "val"],
                  "columntypes": ["integer", "text"],
                  "columnvalues": [58, "new value"]
              }
      ]
  }

• Update changes (two rows):

  {
      "change": [
              {
                      "kind": "update",
                      "schema": "public",
                      "table": "temp",
                      "columnnames": ["id", "val"],
                      "columntypes": ["integer", "text"],
                      "columnvalues": [2, "updated value"],
                      "oldkeys": {
                              "keynames": ["id"],
                              "keytypes": ["integer"],
                              "keyvalues": [2]
                      }
              }
              ,{
                      "kind": "update",
                      "schema": "public",
                      "table": "temp",
                      "columnnames": ["id", "val"],
                      "columntypes": ["integer", "text"],
                      "columnvalues": [1, "updated value"],
                      "oldkeys": {
                              "keynames": ["id"],
                              "keytypes": ["integer"],
                              "keyvalues": [1]
                      }
              }
      ]
  }

• Delete changes (one row):

  {
      "change": [
              {
                      "kind": "delete",
                      "schema": "public",
                      "table": "temp",
                      "oldkeys": {
                              "keynames": ["id"],
                              "keytypes": ["integer"],
                              "keyvalues": [51]
                      }
              }
      ]
  }

• Frontend Backend Protocol -- the chapter covering both Replication and Extended Query Protocols.
• Streaming Replication Protocol
• Logical Replication Message Formats
• Protocol Message Format