saws Shorten urls and earn money Join now and earn on every link you shortenIn the beginning was the World Wide Web, built on HTML.Then came the Social Web, built on personalization.But we believe that there is a third web yet to be built: the Machine-Payable Web, built on Bitcoin.Technologists have desired a Machine-Payable Web for quite some time.In fact, for 20 years the official HTTP specification has actually included a code for this purpose, marked specifically for future use: 402 - Payment Required.With 21, we've done our best to help bring that future about.21 is free software that implements the Payment Required HTTP status code and much more.It makes it easy to (a) send and receive micropayments over HTTP and (b) write new kinds of programs that use this basic technology as an intrinsic primitive, like machine-payable APIs and intelligent agents.If these concepts interest you, and if the idea of a third web based upon machine-to-machine micropayments is exciting, it may be worth your time to learn 21.

This quickstart guide will introduce you to the capabilities of 21, free software that makes it easy to programmatically buy and sell digital goods for bitcoin.You can think of 21 in four different ways: App: The simplest way to understand 21 is as a command line application that you can quickly install on any device to get bitcoin in a variety of ways.Marketplace: The next way to understand 21 is as a marketplace which allows you to trade API calls (and thereby machine resources) for bitcoin.You can view the directory of API calls available for sale at 21.co/mkt, and you can use 21 to publish your own machine-payable APIs with a few keystrokes.Network: The third way to understand 21 is as a sort of "capitalist network", where you can monitor the earnings of your various machines and find other developers who are building machine-payable services.Library: The final way to understand 21 is as a Python 3 library called two1, which allows you to build your own custom machine-payable applications.

With two1 you can add micropayments to new or existing web services with one line of code.As each of these pieces interfaces with the others, the best way to understand them is to learn by doing.So let's get started by installing 21, and then explore each of these four aspects in turn.Before you proceed, please note that 21 is currently in beta, and some of the commands (especially 21 sell) involve running a server locally.While we strive to be security conscious, it's best during the beta phase to install 21 on a 21 Bitcoin Computer, a DIY Bitcoin Computer, an Amazon Virtual Machine, an old computer, or some other standalone device that is not your main personal laptop.21 is currently supported on Ubuntu Linux 14.04 run on Amazon AWS and Mac OS X 10.7+.Most functions are also supported on other Debian-based platforms, such as 21 Bitcoin Computers or DIY Bitcoin Computers.Support for other platforms is coming soon.

Just type this at the command line: Feel free to preview the script before installation.Note that the use of https is mandatory here.Once you've installed the script, please visit the signup page to create your 21 account.bitcoin expo nycOnce you've installed 21 and set up your 21 account, you can log in to your 21 account at the command line as follows: Here's what that looks like: As shown, you will first be prompted to create a Bitcoin wallet.mit bitcoin bezahlen schweizFollow the instructions, and be sure to record the mnemonic provided to you.bitcoin-qt on tailsThis is the backup for access to your wallet.bitcoin fogger

Please note that 21 cannot help you restore your Bitcoin wallet if you lose the mnemonic.Next, you'll be prompted to enter the 21 username you just created along with your 21 password.Before proceeding, we recommend making your system password secure by running passwd if you have not already done so (your system password is distinct from your 21 password).cara mendapatkan bitcoin mudahNote: this section only applies to users of the 21 Bitcoin Computer, virtualized Docker, and Amazon EC2.bitcoin to uroWhen a new device connects to the internet it typically acts as a client, namely something that can initiate connections to domains to download information.However, the 21 software also allows your machine to act as a server that sells machine-payable resources for bitcoin.To do this, it needs to allow other machines to be able to send packets to your machine to request digital goods without knowing the specific machine IP address or domain name in advance.

Run the following command to join the network: This command makes your machine join a virtual private marketplace where other computers on the 21 network can buy and sell files with you directly.As shown, the command will warn you about the risks of joining the network and inform you that it may need superuser permissions to run.If it doesn't print any other error messages, that means you've successfully joined the network, which you can confirm by running 21 market status.Note: After running 21 market, your machine will be on a private network with a virtual IP.The main difference from the internet is that every virtual IP on this network is running 21, and therefore has a bitcoin wallet plus the ability to buy and sell digital goods for bitcoin.It would be nice if all of the other computers on this network were friendly, but we cannot guarantee it.During the beta period, running 21 on a standalone device like a VM or a 21 Bitcoin Computer will provide an added level of security.

You can now test that your installation is fully functional by running the following command.As shown, the command will print a status report that confirms everything is working correctly or else give a list of errors that need to be fixed.If you've attempted to resolve these errors and you need help with your 21 installation, please don't hesitate to go to our Slack channel.Now that you've installed 21, the simplest way to understand it is as a command line app that allows you to quickly get bitcoin on any device in a variety of ways.Specifically, 21 allows you to obtain bitcoin in one of several complementary ways: 21 also allows you to see how much bitcoin you have, and where you got it from.All of these things can be done programmatically via the two1 library, but we will first show how to do them manually by going through several commands: Let's go through these in turn.You can check how much bitcoin you have by running the following command: The output will look similar to the following, but with your personal information substituted.

There are four lines under 'Total Balance' worth discussing: Your spendable buffer at 21.co.To improve performance, 21.co buffers payments from itself and from other users who send from their buffers.This buffer allows users to spend bitcoin amounts smaller than the current 3000-5000 satoshi minimum enforced by some Bitcoin miners.The size of the buffer is currently limited to a maximum of about $10 USD, and can be used to make what we call "off-chain payments" for API calls.Note that off-chain buffer cannot be sent directly to other users; it is purely for increasing performance and can only be used within the 21 system.To send bitcoin to other users you must use your on-chain Bitcoin balance.Your spendable balance on the Blockchain.These are the on-chain satoshis you've received on the Bitcoin Blockchain.They are exclusively controlled by your wallet, with the private keys locally stored on the machine where you are running 21 status.

This balance can be used to make what we call "on-chain payments".Your spendable balance in Payment Channels.These are the satoshis you've deposited into a micropayment channel, which is a blockchain-based smart contract that allows you to send and receive payments down to a single satoshi without having to use a third-party buffer like the 21.co buffer.We'll discuss micropayment channels in more detail later in this tutorial.Amount flushing from 21.co buffer to Blockchain balance.These satoshis are being moved from your buffer to your blockchain balance; this requires confirmation from a Bitcoin miner which typically takes from 5 to 20 minutes.We'll discuss 21 flush in a subsequent section.One important note: your off-chain buffer is associated with your 21.co account, but your on-chain balance is associated with your local machine.If you set up 21 on another machine but log in with the same account, the off-chain buffer value will be the same but the on-chain balance will be different.

This is by design - it allows you associate multiple wallets with your 21 account while keeping full control of the private keys.To sum up: run 21 status to know how much bitcoin you have and where it is located.If you are running it on a clean installation, you will have zero bitcoin.Let's start fixing that.If you browse to your profile page by clicking your profile icon in the top-right corner of this page, visiting your profile, and then clicking Edit, you'll see the option to connect your 21 account to various social accounts: Click any one of the buttons and you'll be directed to a page where you can confirm you want to link the indicated social media account to your 21 account.For more information, please see the Network section later in this document.After you've connected a social account, you may receive an instant increase to your buffer, so check your amounts: To earn more satoshis, you can use 21 sell as described later in this document.

Another way to get bitcoin is by mining it with 21 mine.Note that this command only works on a 21 Bitcoin Computer.Upon first invocation, it starts the onboard mining chip as shown: After this point, it continues mining bitcoin in the background, which you can see by doing 21 mine --dashboard.If invoked again, it allows you to mine bitcoin in the foreground.You can run 21 log at any time to see when you have mined bitcoin either in the background or foreground.Perhaps the most interesting and novel way to get bitcoin with 21 is to sell microservices for bitcoin.21 makes it easy for you to start selling microservice APIs immediately from any computer or device.You don't need to worry about finding a buyer for these microservices; 21 takes care of that for you through the 21 marketplace.The services which provide those APIs are isolated from the rest of your system by placing them in a sandbox, which doesn't guarantee security but which does significantly enhance it.

(Even still, during the beta period you should consider running 21 on a standalone device, like a 21 Bitcoin Computer or an Amazon VM.)The easiest way to get started is to activate all of the microservices bundled with 21 at once by running the following command: If this is your first time running 21 sell, you will be prompted to install its dependencies.Example output is shown below, but the actual output you see will vary by your platform and what dependencies you already have installed.On Linux, the output above will be different because you'll have to log out of your system account (not your 21 account), log back in, and then run 21 sell start --all again to complete the setup.You can also start an individual service, such as ping21, by specifying its name instead of the --all flag.Note that for the initial release of the 21 beta, the ping21 microservice is the only one bundled with 21, but more will be forthcoming.You can check the status of your microservices at any time by running the following command: The output will vary by platform and by which services you're running, but it should look similar to the example below: The concept behind the ping21 microservice is that you are renting out your machine (along with many others) for distributed uptime monitoring.

For further information, see here and here.You can stop selling all microservices with a single command: The output will look similar to the following: You also stop an individual service, such as ping21, but specifying its name instead of the --all flag.For security, the services run by 21 sell each have their own wallet separate from your main wallet.This reduces the risk that one compromised service can steal funds earned by other services or which you acquired in other ways.This means that before you can spend the satoshis you earned with 21 sell, you have to move them to your main wallet.The 21 sell sweep command will do that for you: This will move your sell balance to your main wallet.For now, let's make sure all services are running so that you can earn bitcoin in the background while you continue this tutorial: You can track when you've receive bitcoin and from where with 21's log command.This will provide you with an ordered list (most recent first) of all your activity.

Depending on whether or not you've earned any satoshis you using 21 sell, your output may look similar to the following: In addition to selling, earning, and mining bitcoin, you can also use 21 to buy up to $100 worth of bitcoin per day at the command line through the 21/Coinbase integration.If you don't have a Coinbase account already, please create one.Start by opening the 21.co homepage and clicking either the Login button on the top-right corner or your profile picture if you're already logged in.On your profile page, click the line that says, Link Coinbase.This will open a popup that explains what will happen in the linking process.Click the Link account button to continue.A new window will open (if it doesn't, please check your browser toolbar and choose Allow pop-ups from 21.co; then click the Link account button again).Enter your Coinbase username and password.If you have two-factor authentication enabled on Coinbase, enter the code you received using either the Google Authenticator app, an SMS message that Coinbase sent to your phone, or the voice phone call Coinbase made to your phone.

Coinbase will now display the permissions that we need to authorize a purchase on your behalf.Please read the permissions list carefully, and if you agree, click the Authorize button.If you don't have a payment method setup, Coinbase will walk you through setting one up.If you already have a payment method setup, Coinbase will automatically skip this step.Once you have a payment method set up, Coinbase will close its window and return you to the 21.co account linking page.A summary of your payment details will be displayed.Click the X in the top-right corner to exit the pop-up.Your 21 and Coinbase accounts are now linked.To confirm that your accounts are linked, open up a terminal and run the following command: Now you can get price quotes as follows.These are useful to figure out exactly how much bitcoin you want to buy.The output will look similar to the following, although the prices you receive will be much more recent: Here's how to buy 450,000 satoshis (0.0045 BTC): A message similar to the one below will be displayed telling you how much bitcoin you're about to purchase and what fees you will have to pay.

To confirm that you want to buy, type y and press enter: After you confirm by pressing y, you should see the following message confirming you purchased bitcoin.The time to deposit bitcoin into your on-chain wallet will vary with how much verification you've done at Coinbase.New accounts may take days to confirm, but if you have "instant buy" set up, bitcoin should be deposited from Coinbase into your local Bitcoin wallet within 5-20 minutes.This delay occurs because the transaction needs to confirm on the Bitcoin Blockchain where blocks are only added on average every 10 minutes.You can run the following command to check your on-chain balance at any time: And to see a history of your 21 buybitcoin purchases: As noted above, users have a small off-chain buffer as a performance improvement.Users with 20,000 satoshis or more in this buffer can flush all or part of the buffer to their local wallets by running the 21 flush command.

Please note: the satoshis you withdraw from your buffer cannot be added back.Since you need satoshis in your buffer to run many of the 21 tutorials, we recommend that you be careful not to flush all of your buffer.When used without any parameters, your full buffer is flushed.However, you may also specify the amount you want flushed: Which will produce output similar to the following: Other units allowed are bitcoin for bitcoin (100 million satoshis) and USD for an approximate number of satoshis using the most recently available BTC/USD price.After the flushing completes and Bitcoin miners confirm the transaction, those satoshis will be available in your on-chain balance.Note that this will only work if you have at least 20,000 satoshis in your buffer as shown by 21 status.If you have fewer than 20,000 satoshis, you can run 21 mine on a 21 Bitcoin Computer or 21 sell on other supported devices to earn more satoshis, which you can then flush.

Note: before proceeding to the next step, please follow these instructions: Increase your buffer to at least 163,000 satoshis using 21 sell or other methods.Flush those satoshis to your blockchain balance by running 21 flush 163000 satoshis When combined with the 20,000 satoshis you flushed above, this should give you a total blockchain balance of 183,000 satoshis Increase your buffer to at least 20,000 satoshis again using 21 sell or another method.The above instructions will give you the necessary balance and number of spendable "outputs" on the blockchain to be able to follow the rest of this tutorial with minimum interruption.If you have on-chain balance from flushing, selling, or buying bitcoin, you can use the following command to send your bitcoin to another address: The following denominations are valid: satoshis, bitcoin, and usd.The second way to understand 21 is as a marketplace.We touched on this above, but the marketplace part of 21 is why 21 sell works.

You can't just sell machine-payable services into the ether - there must be a buyer, which the 21 marketplace provides after you start 21 sell.21 exposes several commands for working with the 21 marketplace, including: The purpose of the search, buy, and rate commands is fairly self-explanatory, as they have analogs in other marketplaces.As for the sell and publish commands, the best way to think of the distinction is to remember the difference between 'starting a web server' versus 'submitting your website to the Google index'.21 sell is analogous to starting a web server, whereas 21 publish is analogous to submitting your website to a search index.We covered 21 sell in the previous section, and we will cover 21 publish in a subsequent section.In this part of the tutorial, we're going to search for an endpoint in the 21 marketplace and use the satoshis from the previous section to make a purchase.But before we get into any of these commands, let's take a look at the web interface to the 21 marketplace itself at 21.co/mkt.

In the marketplace screenshot above, two apps are shown: a part of speech tagger and a zip code database.Prior to taking this screenshot, we clicked on the zip code data app summary in order to expand its listing.Each app has its title in bold, followed by the name of its publisher and a short description.On the right side is the price to use the app in U.S.dollars (estimated based on the current exchange rate) followed by the price in satoshis (the actual price you'll pay).A star rating under the prices shows the average rating marketplace participants have given this app followed by the number of people who have rated it.This is the only field in the description that is not under the control of the person who published the app.We'll describe how to rate an app later in this tutorial.In the expanded app description shown in the screenshot above for the zip code data app, there are three tabs.The first tab (opened) shows the usage information for the app, including the command to run to buy that app's API call from the 21 command line as well as its sample output (prefixed with comments so you don't actually try to run the output).

The second and third tabs (not shown) provide additional information about the app's uptime and its API.This information may be empty for apps that have not provided that additional information.There are two ways for you to find useful endpoints in the 21 marketplac.The first is from the search bar on top of the marketplace home page.The second is from the 21 command line.For example, to search for apps that mention "zip" in their title or description, run the following command: The output should look something like this: If you enter the identifier (ID) for a particular app, more details will be shown.For example, if you type EJZ for more details about the zip app, you should see something similar to this: The instructions at the bottom of the listing provide complete instructions for the search interface.When you view the additional details of an app using either the detail listing on the website or the command line search interface, you'll be shown the quick buy instructions.

You can use that command to purchase the endpoint.For example, we'll buy the zip code data endpoint using its default example: The output returned should look like this: Note that you were able to buy this API directly for bitcoin without any API key or credit card signup.For more details, see here.Once you've purchased an endpoint, you should consider rating it.Endpoints with good ratings tend to rank higher in the marketplace than endpoints with poor ratings, and we expect that people are a lot more willing to purchase from endpoints with high star ratings than endpoints with low star ratings.To rate an app, you'll need to know its ID code, which is the same code you used to get more information about it in the 21 search command line interface.For example, to give a 5-star rating to the zip code app we just used, we would run the following command: Which would return the following result: The third way to understand 21 is as a network.

The machines in the marketplace that are using 21 to buy and sell digital goods are (after all!)owned by humans, and facilitating commercial connections between them can be valuable as well.Towards this end, every 21 user who registers an account receives a profile page.If your 21 username is satoshi, then your profile page is 21.co/satoshi.When you're logged in, you can change information on your profile page by clicking the Edit button in the top-right corner of your profile.The screenshot above adds numbers near the various parts of the profile.Those fields are: Profile picture: by default this is a gold letter based on your name, but you can change it to a custom profile picture by clicking on the Edit button.Name: by default this is the name of your account, but you can set it to another name by clicking the Edit button.Account name: this is always your account name.Bio: by default, this is empty, but you can fill it in by clicking the Edit button.

Social media links: by default, these buttons will appear in grey, but if you click the Edit button and provide additional information, the buttons will turn black and link to your Twitter, GitHub, and LinkedIn profiles.Edit & logout buttons: the edit button will allow you to change various information on your profile, and the logout button will exit the session and show you what your profile looks like to everyone else.Off-chain buffer: the bottom number is the exact number of satoshis you have in your 21.co buffer, which we call the off-chain buffer.The top number is the estimated value of those satoshis in U.S.We don't track or display any satoshis stored in your on-chain wallet (where you control the private keys directly).Coinbase status: by default, this provides a link you can use to begin setting up buy bitcoins with Coinbase.If you've already linked your 21 and Coinbase accounts, this says "Coinbase Linked" and you can click it again to unlink your accounts.

Your apps: listed here are any apps that you have active on the marketplace, or a link to documentation for building your first app.Now is a good time to update your public profile by clicking the Edit button.The edit screen allows you to update all of the fields on your profile, add a profile image, and also change or reset your password.As you go through the following sections where you create, pay, and publish an app, you may want to periodically refresh your profile page to see it update.The fourth and final way to think of 21 is as a library.Specifically, the 21 Python 3 library (known as two1) allows you to quickly add bitcoin micropayments capability to any new or existing web service with one line of code.These machine-payable applications can then be published to the 21 marketplace, where other machines running 21 can buy them for bitcoin.If you're an experienced developer, full developer documentation is also available.Let's learn how to use two1, which is the Python 3 library version of 21.

To begin, we'll need to install the Flask website microframework: Now, here's a simple "hello, world" app that uses two1 to charge 5000 satoshis to return some text: = .()=) The key lines of code above are the ones that instantiate instances of the Wallet and Payment class.The Wallet looks for a wallet directory which is by default in .two1/wallet, from which it instantiates a full programmatic HD wallet.The Payment constructor in turn takes both a Flask app instance and a Wallet instance and builds a datastructure that can handle three kinds of micropayments for web-payable services.Type that into a text file named hello-world.py and run the program using the following command: If there are no problems, it will continue to run after you start it as it waits for incoming connections.We are going to test this code by buying from it using all three kinds of micropayments: off-chain buffers, on-chain bitcoin, and on-chain payment channels.

Let's test the hello-world.py server by buying from it using the first of the three payment modes that 21 supports, namely off-chain buffers.This is currently the default payment for 21 buy, so we'll test it first.Because hello-world.py is running in your old terminal, you should open a new terminal.If you're using a 21 Bitcoin Computer or other remote server, you can do this by SSHing into a new terminal.Then check your current buffer by running the following command: Now purchase the hello world endpoint using the following command: The output will look something like this (your 21.co buffer will likely be different): Because you paid yourself using a free off-chain transfer, your actual buffer will not have changed.You can confirm this by running the status command again: However, you will see the activity in your log: You will see that you bought and sold from yourself, resulting in 0 net change to your buffer.

The second of the three payment methods that 21 supports are on-chain payments made using Bitcoin transactions that get added to the Bitcoin blockchain.To use on-chain transactions there's a minimum valid payment size (currently 3000-5000 satoshis) to have your transaction included on the blockchain and you must pay a transaction fee to Bitcoin miners.Because of the fee, you will see your total balance go down when you make the following on-chain payment - even though you're paying yourself.Let's repeat the instructions from the previous section with one modification to make the purchase on-chain.First print your current balance; pay attention to the on-chain balance: Now purchase the hello world endpoint on-chain: The output will look something like this (your 21.co buffer will likely be different): If you get an error indicating that you have too low a balance, you will need to get more satoshis (or wait for more people to buy from your 21 sell endpoints).

You will then need to run 21 flush 20000 satoshis to move those satoshis to your on-chain balance, and finally you will need to wait about 5 to 20 minutes for the flush to complete.Because you had to pay a transaction fee to miners for this transaction, you'll see that your on-chain balance has changed in status: The third of the three payment methods that 21 supports are Bitcoin micropayment channels.Channels are a type of on-chain transaction that are optimized for repeat transactions to the same service provider.As motivation, the fee you paid for the previous on-chain transaction probably seemed quite high compared to the 5000 satoshi cost of the API you purchased.Fortunately, 21 allows you to amortize those fees over many API requests through something called micropayment channels.How does this technology work?A good analogy is the idea of a bar tab.When you go to a bar, you typically put down a credit card to open a tab, enjoy your food and drinks, and then close out the tab at the end of the night.

This means just two "transactions" (opening and closing the tab) even if there were many rounds of food and drink for your party.Reducing the transaction overhead is more convenient for both you and the busy bartender, as you don’t need to pull out your card and they don’t need to pay credit card fees for every pour of every drink.Similarly, opening a micropayment channel is like opening a bar tab.In between when you open and close the channel, an unlimited number of payments of any value may be made, up to the amount you configure when you open the channel.Let's repeat the instructions one more time with the modifications necessary to use a micropayment channel.First, print your current balance; again pay attention to your on-chain balance.Now purchase the hello world endpoint with a micropayment channel: If you receive an error message about not having a large enough balance, that is because payment channels require at least 123,000 satoshis to open (100,000 for payments; 20,000 for transaction fees; 3,000 to refund to you no matter what).

If you receive the following prompt, choose y to open the channel.The output should look like this: You should notice two changes: Your on-chain balance is 123,000 satoshis lower than it was because the micropayment channel amount was subtracted from this balance.You now have a payment channel balance listed.After buying the API above, it should be 95,000 satoshis.It's not shown here, but when you close the payment channel, you'll receive back the 95,000 satoshis you haven't spent yet, the 5,000 satoshis you spent to your own API endpoint, and the 3,000 satoshis which are the guaranteed refund.That required a fair bit of setup, but here is the key: now if you purchase the endpoint again, it will reuse the existing micropayment channel: And the output will look like this: That's the payoff.You can now do an unlimited number of rapid bitcoin micropayments (well, up to the value of your deposit) for the cost of the open and close channel transactions.

Note that the payment channel you just opened will close automatically by default after about 5 days.If you want to close it sooner or want to learn more about 21's secure micropayment channels, you'll find more information in the following documents: Note: this section only applies to users of the 21 Bitcoin Computer, virtualized Docker, and Amazon EC2.You just built the simple hello-world.py API with two1 and tested it with all three micropayment methods supported by 21.Now we will show you how to publish it to the 21 marketplace with 21 publish.The first step is to create a manifest file.We provide detailed documentation to help you create manifest files, but you can use the file below for this simple hello world app.First open a file named manifest.yaml: Then paste in the following content.:: : : : : :: : :: : : :- : / Where the example content above says "TODO", you will want to update the corresponding line with the correct information.

Once you have added that information to the manifest, save the file and exit the text editor.Then restart the hello world app by re-running the same command from before: Now go to your second open terminal and publish your app by running the following the following command: If it's successful, the output will look like this: After you publish your app using the instructions above, wait about 15 seconds and then search for your app the same way we did in the 21 search section: The output should look something like this, although there may be more hello world apps in the marketplace when you do this.You can find your particular app by looking at the username field: You can also search using the web page.Now that your app is listed, you can either buy it from yourself or (more interestingly) find someone to buy from you.A good place to find folks willing to buy from you is our Slack Channel at slack.21.co.The command to buy it should be in the quick buy section of the marketplace description since you provided your IP address or Zerotier IP address in the manifest file earlier.