21 IncJohn Granata
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In this tutorial we'll show you how to set up your 21 Bitcoin Computer as a server that will allow anyone to send you an SMS for a small amount of bitcoin - without revealing your phone number. The example can be extended to any other form of out-of-network social messaging, such as an email from someone you haven't met or a Twitter DM from someone you haven't followed. It's a way to monetize your inbox and widen the circle of people who can contact you.
You will need the following items:
- A 21 Bitcoin Computer, with built-in mining and software
- The latest version of the 21 software, obtained by running
21 updateas described in the [setup][19] process. - Do the [Introduction to the 21 Bitcoin Computer][20] tutorial
- Do the [Working with Multiple 21 Users][21] tutorial
If you've got all the prerequisites, you are ready to go. Let's get started!
Follow the instructions in the
[Working With Multiple 21 Users][21] tutorial to set
up the twenty-client, twenty-server, and twenty-server-2 users
and install Flask.
Go to [twilio.com][22] and create an account. Take note of your [account SID][23], auth token, and Twilio phone number. Then install the Twilio Python3 package:
sudo pip3 install twilio
We'll use this to send the SMS.
Now log into the Bitcoin Computer as the twenty-server user:
ssh twenty-server@<BITCOIN_COMPUTER_IP_ADDRESS>
Create a folder to house your project:
mkdir bitcoin-sms-server && cd bitcoin-sms-server
Use a text editor to create a file called sms-server.py in the
bitcoin-sms-server directory, and fill it with the following code:
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import os
from twilio.rest import TwilioRestClient
from flask import Flask, request
# import from the 21 Bitcoin Developer Library
from two1.lib.wallet import Wallet
from two1.lib.bitserv.flask import Payment
app = Flask(__name__)
wallet = Wallet()
payment = Payment(app, wallet)
# create the twilio rest client
client = TwilioRestClient(
os.environ.get('TWILIO_ACCOUNT_SID'), os.environ.get('TWILIO_AUTH_TOKEN')
)
@app.route('/send-sms')
@payment.required(1000)
def send_sms():
"""Send an sms for bitcoin"""
text = request.args.get('text')
response = client.messages.create(
to=os.environ.get('MY_PHONE_NUMBER'),
from_=os.environ.get('TWILIO_PHONE_NUMBER'),
body=text
)
return "Message sent."
# set up and run the server
if __name__ == '__main__':
app.run(host='0.0.0.0')
Save the file and close it. Set environment variables in your terminal as follows:
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export TWILIO_ACCOUNT_SID=<Your Twilio Account SID>
export TWILIO_AUTH_TOKEN=<Your Twilio Auth Token>
export TWILIO_PHONE_NUMBER=<Your Twilio Phone Number>
export MY_PHONE_NUMBER=<Your Phone Number>
Start the micropayments server:
python3 sms-server.py
Your bitcoin-powered SMS endpoint is up and running! Let's get a client user set up to test the endpoint.
Leave your twenty-server session open, but open a new terminal on
your regular computer/laptop (or PuTTY session on Windows) and SSH
into your 21 Bitcoin Computer, this time as the twenty-client
user. Create a project folder called bitcoin-sms-client and a file
called sms-client.py with the following code:
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import urllib.parse
# import from 21 Bitcoin Developer Library
from two1.commands.config import Config
from two1.lib.wallet import Wallet
from two1.lib.bitrequests import BitTransferRequests
wallet = Wallet()
username = Config().username
requests = BitTransferRequests(wallet, username)
# request the bitcoin-enabled endpoint you're hosting on the 21 Bitcoin Computer
def testendpoint(sms='I just paid you bitcoin to send you this message!'):
# In a real application you would escape this message to prevent injections
message=urllib.parse.quote_plus(sms)
response = requests.get(url='http://localhost:5000/send-sms?text='+message)
print(response.text)
if __name__ == '__main__':
import sys
testendpoint(sys.argv[1])
You can run this client script from the command line to test your SMS endpoint:
python3 sms-client.py 'I am SMSing you for bitcoin!'
You should receive a text message at your phone number. Congratulations, you just set up a way for someone to send you a text message for bitcoin!
You've learned how to build a very simple app in which someone outside your social network can pay you bitcoin to contact you. This is actually something that people have wanted on the internet for a very long time, since the development of [Hashcash][82] and before. Here are some ideas for what to build next:
- Extend the example to escape the input text message and otherwise be robust against bad input strings
Add support for paying bitcoin to contact you via [email][83], [Facebook][84], [Twitter][85], [LinkedIn][86] , and other forms of social messaging. * Create an inbox viewer which rank orders your received messages not by the time they were received, but by the amount of bitcoin sent with them (a new kind of "priority inbox") * Make this example high performance by replacing the simple Flask server with a proper deployment on the underlying hardware. See [this][87] and [this][88] for more information.
If you build anything like this and want to earn some bitcoin for your efforts, write it up and submit it as a [bitcoin tutorial][89]. If we decide to publish it on our site, you'll win $200 in BTC!
You can also come to our Slack channel at slack.21.co to find other folks with 21 Bitcoin Computers to post your endpoints and give feedback. We look forward to seeing you there!
Just as a reminder, you can send bitcoin mined or earned in your
21.co balance to the blockchain at any time by running 21 flush . A transaction will be created within 10 minutes,
and you can view the transaction id with 21 log.
Once the transaction has been confirmed, you can check the
balance in your bitcoin wallet from the command line with
wallet balance, and you can send bitcoin from your
wallet to another address with wallet sendto $BITCOIN_ADDRESS $BTC_AMOUNT --use-unconfirmed. Make sure
to use the amount in BTC, not in Satoshi; the
--use-unconfirmed flag ensures that you can send even if you
have unconfirmed transactions in your wallet.
Ready to try out your bitcoin-payable server in the wild? Or simply want to browse and purchase from other bitcoin-enabled servers? Head over to the [21 Developer Community][90] at slack.21.co to join the bitcoin machine-payable marketplace hosted on the 21 peer-to-peer network.
Check out all the Bitcoin Apps you can build with the 21 Bitcoin Computer.
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Authors
John Granata
If you have any questions or issues, please drop us a line at [[email protected] ][92] or join our Slack community.
This content is licensed under a [Creative Commons Attribution-ShareAlike 4.0 International License][93].
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(c) 2016, 21.co
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