Slack Socket Mode

Installation

$ npm install @slack/socket-mode

Usage

These examples show the most common features of Socket Mode. You'll find even more extensive documentation on the package's website.

Initialize the client

The package exports an SocketModeClient class. Your app will create an instance of the class for each workspace it communicates with. Creating an instance requires a app level token from Slack. Apps connect to the Socket Mode API using the newly introduced app level token, which start with xapp.

Note: Socket Mode requires the scope of connections:write. In your browser, navigate to your app's app config and go to the OAuth and Permissions section to add the scope.

const { SocketModeClient } = require('@slack/socket-mode');

// Read a token from the environment variables
const token = process.env.SLACK_APP_TOKEN;

// Initialize
const client = new SocketModeClient({token});

Connect to Slack

Data from Slack will begin to flow to your program once the client is connected. You'll also be able to send data to Slack after the connection is established. Connecting is as easy as calling the .start() method.

const { SocketModeClient } = require('@slack/socket-mode');
const token = process.env.SLACK_APP_TOKEN;

const socketModeClient = new SocketModeClient(token);

(async () => {
  // Connect to Slack
  await socketModeClient.start();
})();

Listen for an event

Apps register functions, called listeners, to be triggered when an event of a specific type is received by the client. If you've used Node's EventEmitter pattern before, then you're already familiar with how this works, since the client is an EventEmitter.

The event argument passed to the listener is an object. It's contents corresponds to the type of event its registered for.

const { SocketModeClient } = require('@slack/socket-mode');
const token = process.env.SLACK_APP_TOKEN;

const socketModeClient = new SocketModeClient(token);

// Attach listeners to events by type. See: https://api.slack.com/events/message
socketModeClient.on('message', (event) => {
  console.log(event);
});

(async () => {
  await socketModeClient.start();
})();

Send a message

To respond to events and send messages back into slack, it is recommend to use the @slack/web-api package with a bot token.

const { SocketModeClient } = require('@slack/socket-mode');
const { WebClient } = require('@slack/web-api');

const socketModeClient = new SocketModeClient(process.env.SLACK_APP_TOKEN);
const webclient = new WebClient(process.env.BOT_TOKEN);

// Attach listeners to events by type. See: https://api.slack.com/events/message
socketModeClient.on('member_joined_channel', async ({event, body, ack}) => {
    try {
      // send acknowledgement back to slack over the socketMode websocket connection
      // this is so slack knows you have received the event and are processing it
      await ack();
      await webclient.chat.postMessage({
          blocks: [
          {
            type: 'section',
            text: {
              type: 'mrkdwn',
              text: `Welcome to the channel, <@${event.user}>. We're here to help. Let us know if you have an issue.`,
            },
            accessory: {
              type: 'button',
              text: {
                type: 'plain_text',
                text: 'Get Help',
              },
              value: 'get_help',
            },
          },
        ],
        channel: event.channel,
      });
    } catch (error) {
      console.log('An error occurred', error);
    }
  });

Lifecycle events

The client's connection to Slack has a lifecycle. This means the client can be seen as a state machine which transitions through a few states as it connects, disconnects, reconnects, and synchronizes with Slack. The client emits an event for each state it transitions to throughout its lifecycle. If your app simply needs to know whether the client is connected or not, the .connected boolean property can be checked.

In the table below, the client's states are listed, which are also the names of the events you can use to observe the transition to that state. The table also includes description for the state, and arguments that a listener would receive.

The client also emits events that are part of its lifecycle, but aren't states. Instead, they represent specific moments that might be interesting to your app. The following table lists these events, their description, and includes the arguments that a listener would receive.

Logging

The SocketModeClient will log interesting information to the console by default. You can use the logLevel to decide how much information, or how interesting the information needs to be, in order for it to be output. There are a few possible log levels, which you can find in the LogLevel export. By default, the value is set to LogLevel.INFO. While you're in development, its sometimes helpful to set this to the most verbose: LogLevel.DEBUG.

// Import LogLevel from the package
const { SocketModeClient, LogLevel } = require('@slack/socket-mode');
const token = process.env.SLACK_APP_TOKEN;

// Log level is one of the options you can set in the constructor
const socketModeClient = new SocketModeClient({
  token,
  logLevel: LogLevel.DEBUG,
});

(async () => {
  await socketModeClient.start();
})();

All the log levels, in order of most to least information are: DEBUG, INFO, WARN, and ERROR.

const { createWriteStream } = require('fs');
const logWritable = createWriteStream('/var/my_log_file'); // Not shown: close this stream

const socketModeClient = new SocketModeClient(token, {
  // Creating a logger as a literal object. It's more likely that you'd create a class.
  logger: {
    debug(...msgs): { logWritable.write('debug: ' + JSON.stringify(msgs)); },
    info(...msgs): { logWritable.write('info: ' + JSON.stringify(msgs)); },
    warn(...msgs): { logWritable.write('warn: ' + JSON.stringify(msgs)); },
    error(...msgs): { logWritable.write('error: ' + JSON.stringify(msgs)); },
    setLevel(): { },
    setName(): { },
  },
});

(async () => {
  await socketModeClient.start();
})();

Requirements

This package supports Node v10 LTS and higher. It's highly recommended to use the latest LTS version of node, and the documentation is written using syntax and features from that version.

Getting Help

If you get stuck, we're here to help. The following are the best ways to get assistance working through your issue:

• Issue Tracker for questions, feature requests, bug reports and general discussion related to these packages. Try searching before you create a new issue.