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Signal Chat Bot SDK

A Forest of Signal Bots

Forest is a framework for running payments-enabled chat and utility bots for Signal Messenger.

To get familiarized with deploying and running a forest bot, we’ve provided a short tutorial to teach you how to deploy hellobot, the simplest possible forest bot.

See also: https://github.com/mobilecoinofficial/forestbot-template

High Level Overview

In this tutorial you will:

  • Install Prerequisites.
  • Install signal-cli and register a Signal account for your bot.
  • Deploy the bot!

At the end there’s extra information and a guide on how to contribute.

Bring your own phone number

You will need at least 2 Signal accounts to properly test your bot. A signal account for the bot to run on and your own signal account to talk to the bot. To set up an additional signal account for your bot you can use a second phone or a VoIP service such as Google Voice, Forest Contact, Twilio, or Teli.net. All you need is a phone number that can receive SMS.

Installing Prerequisites

Python 3.9

Please refer to the official Python wiki for instructions on installing Python 3.9 on your machine. On Debian/Ubuntu based systems you may run:

sudo apt update
sudo apt install python3.9 python3.9-dev python3-pip


We use poetry to handle dependencies, run:

python3.9 -m pip install poetry

then to install the prerequisites:

poetry install


Signal-cli is a command line interface for Signal. Forest bots run with signal-cli or auxin-cli as the backend. Auxin-cli is beta software, and does not yet allow you to register a new phone number, so for this guide we will use signal-cli.

To install or run signal-cli you will need Java 17. Verify that you have it installed by running:

java --version
openjdk 17.0.1 2021-10-19
OpenJDK Runtime Environment (build 17.0.1+12-Ubuntu-120.04)
OpenJDK 64-Bit Server VM (build 17.0.1+12-Ubuntu-120.04, mixed mode, sharing)

otherwise install with:

sudo apt install openjdk-17-jre-headless

On arch:

sudo archlinux-java set java-17-openjdk

You can then install signal-cli from a pre-built release or build it from source yourself.

Download a pre-built signal-cli release

The maintainers of signal-cli provide precompiled releases you can download and run immediately.

Download and extract the latest release tarball from https://github.com/AsamK/signal-cli/releases



tar -xvf signal-cli-

Verify the installation succeeded

./signal-cli- --version



Finally for ease of use, link the executable to your working directory:

ln -s ./signal-cli- .

./signal-cli --version



Building signal-cli from Source

You can also build signal-cli from source. You can do so by cloning the official repo and running ./gradlew installDist:

git clone https://github.com/AsamK/signal-cli.git

cd signal-cli

./gradlew installDist

Verify the installation succeeded:

./build/install/signal-cli/bin/signal-cli --version



Finally for ease of use, link the executable to your working directory (change the path depending on where you cloned the repo):

ln -s $HOME/signal-cli/build/install/signal-cli/bin/signal-cli .

./signal-cli --version



For more detailed instructions visit the signal-cli repository.

Registering a Signal Account for your bot

As mentioned above, you will need at least 2 Signal accounts to properly test your bot. A Signal account for the bot to run on and your own signal account to talk to the bot. To set up an additional Signal account for your bot you can use a second phone or a VoIP service such as Google Voice, Forest Contact, or Twilio. All you need is a phone number that can receive SMS.

Message Forest Contact on Signal

To register your phone you need a way to pass Signal’s CAPTCHA challenge, and have Signal send you a verification SMS. There are official Signal-cli CAPTCHA instructions on the Signal-cli repo. We’ve also devised a shortcut to register a Signal data store. Input your phone number with the country code (+1 for the US) and then run these commands to generate a Signal datastore in your directory.

sudo apt install jq # install jq in case you don't already have it

export BOT_NUMBER=+15551234567 # number you've obtained for your bot

export CAPTCHA=signal-recaptcha-v2.6LfBXs0bAAAAAAjkDyyI1Lk5gBAUWfhI_bIyox5W.registration.$(curl -s --data-binary "https://signalcaptchas.org/registration/generate.html" https://human-after-all-21.fly.dev/6LfBXs0bAAAAAAjkDyyI1Lk5gBAUWfhI_bIyox5W | jq -r .solution.gRecaptchaResponse)

./signal-cli --config . -u $BOT_NUMBER register --captcha $CAPTCHA

The CAPTCHA command may take a minute or so to complete.

You will receive an SMS with a 6 digit verification code. Use that code with the verify command to verify your phone number.

./signal-cli --config . -u $BOT_NUMBER verify 000000

This will create a data directory that holds your Signal keys and secret data. DO NOT CHECK THIS DIRECTORY INTO VERSION CONTROL. You can use this data directory with signal-cli or auxin-cli. You can test that the registration and verification succeeded by sending yourself a message.

export ADMIN=+15551111111 #your personal signal number

./signal-cli --config . -u $BOT_NUMBER send $ADMIN -m "hello"


Signal-cli will output a timestamp and you should receive a message on your phone.

If you're having trouble registering with this method, there’s a more thorough walkthrough on the signal-cli wiki.

Running Hellobot

If you’ve made it this far, the hard part is over, pat yourself on the back. Once you have a Signal data store, you can provision as many bots as you want with it (as long as only one runs at a time).

Hellobot is the simplest possible bot, it is a bot that replies to the message “/hello” with “hello, world”. You can see the code for it in sample_bots/hellobot.

Hellobot will read environment variables from a secrets file. By default it looks for a file called dev_secrets. Create a file called dev_secrets with the following information on it (replace ADMIN with your personal number and BOT_NUMBER with the number you registered with signal-cli). DO NOT CHECK THIS FILE INTO VERSION CONTROL. Look at the end of the document for explanations of the other environment variables in the dev_secrets file.




Finally you can run hellobot with

poetry run python -m sample_bots.hellobot

You should see an output like this:

INFO utils:56: loading secrets from dev_secrets

INFO core:48: Using message parser: <class 'forest.message.StdioMessage'>

INFO payments_monitor:111: full-service url: http://localhost:9090/wallet

INFO datastore:96: SignalDatastore number is +15551234567

WARNING datastore:225: not setting up tmpdir, using current directory

INFO core:118: ['./signal-cli', '--trust-new-identities', 'always', '--config', '.', '--user', '+15551234567', 'jsonRpc']

======== Running on ========

(Press CTRL+C to quit)

Now you can text your bot “/hello” and it should reply with “hello, world”.

Default forest commands

Every forest bot comes with some pre-packaged commands. You can test these with your hellobot. Try sending it “/printerfact” to learn a real fact about printers. /help will display all the available commands for any given bot. /help [command] will explain what the command does. The default commands are.

/help : prints available commands and information about a given command /ping : replies with pong /printerfact : prints a fact about printers

Write your own bot!

You can add new commands by modifying hellobot.py. Notice the command structure “do_hello”. Anything after do_ will become a slash command. Add the following command to hellobot.py and redeploy to see it in action:

async def do_goodbye(self, message: Message) -> str:

        return "Goodbye, cruel world!"

And with that you’ve deployed your first forest bot. Congratulations!

Next Steps and Further Information

This is just the beginning. The forest framework provides a lot more functionality, and there are a couple more complex bots in the repo as well. One of the main functionalities of forest bots is that it’s easy to enable Signal Payments for them so that your users can pay your bot in $MOB. This allows your bot to collect donations or sell content. To learn about the payment functionalities, and build your first payments-enabled forest bot, check out /echopay.

Storing your Signal keys

Forest provides a helper program to upload your data directory to a Postgres database. Once you have provisioned a database (e.g. via http://supabase.com or https://fly.io/docs/reference/postgres), add this line to your dev_secrets file.

DATABASE_URL=postgres://<your database url>

Then, you can upload your datastore with:

./forest/datastore.py upload --number $BOT_NUMBER --path . --note "this number is for my special bot"

Options and secrets

These are the environment variables and flags that the bots read to work. Not all of them are necessary for every bot. As you saw, hellobot only used a subset of these.

  • ENV: if running locally, which {ENV}_secrets file to use.
  • BOT_NUMBER: the number for the bot’s signal account
  • ADMIN: admin’s phone number, primarily as a fallback recipient for invalid webhooks; may also be used to send error messages and metrics.
  • ADMINS: additional list of people who can use admin commands
  • ADMIN_GROUP: group to get admin messages. all messages in that group will have admin
  • DATABASE_URL: URL for the Postgres database to store the signal keys in as well as other information.
  • FULL_SERVICE_URL: URL for full-service instance to use for sending and receiving payments
  • CLIENTCRT: client certificate to connect to ssl-enabled full-service.
  • ROOTCRT: certificate to validate full-service.
  • MNEMONIC: account to import for full-service. Not Secure.
  • SIGNAL: which signal client to use. can be ‘signal-cli’ or ‘auxin-cli’. Defaults to auxin.
  • ROOT_DIR: specify the directory where the data file is stored, as well as where the signal-cli executable is. Defaults to /tmp/local-signal if DOWNLOAD, /app if running on fly, and . otherwise
  • SIGNAL_PATH: specify where the signal client executable is if it is not in ROOT_DIR.
  • LOGLEVEL: what log level to use for console logs (DEBUG, INFO, WARNING, ERROR). Defaults to DEBUG
  • TYPO_THRESHOLD: maximum normalized Levenshtein edit distance for typo correction. 0 is only exact matches, 1 is any match. Default: 0.3
  • SIGNAL_CLI_PATH: path to executable to use. useful for running signal-cli with graalvm tracing agent
  • GOOGLE_MAPS_API: google maps api key
  • PAUTH: used for PersistDict; see </pdictng_docs/README.md>
  • SALT: used for PersistDict
  • METRICS_SALT: used for logging when users were first and last seen. Must be set to log

Binary flags

  • DOWNLOAD: download/upload datastore from the database instead of using what’s in the current working directory.
  • UPLOAD: can be used to upload as a backup without downloading
  • AUTOSAVE: start MEMFS, making a fake filesystem in ./data and used to upload the signal-cli datastore to the database whenever it is changed. If DOWNLOAD, also create an equivalent tmpdir at /tmp/local-signal, chdir to it, and symlink signal-cli process and avatar.
  • MONITOR_WALLET: monitor transactions from full-service. Relevant only if you’re giving users a payment address to send mobilecoin to instead of using signal pay. Experimental, do not use.
  • LOGFILES: create a debug.log.
  • ADMIN_METRICS: send python and roundtrip timedeltas for each command to ADMIN.
  • ENABLE_MAGIC: use string distance and expansions


We accept Issues and Pull Requests. These are our style guides:

Code style: Ensure that mypy *py and pylint *py do not return errors before you push.

Use black to format your python code. Prefer verbose, easier to read names over concise ones.

pip install black pylint mypy types-protobuf types-termcolor

Install black pre-commit hook with ln -s (readlink -f .githooks/pre-commit) .git/hooks/pre-commit on fish, or ln -s $(readlink -f .githooks/pre-commit) .git/hooks/pre-commit on bash. Requires black to be installed.