Node.js

18_3_Accessing_Bitcoind_with_NodeJS.md

@@ -67,14 +67,190 @@ $ npm init
 $ npm install bcrpc
 ```
 
-## Manipulate Your Wallet
+In this ```myproject``` directory, create a file called ```server.js``` in which the JavaScript code can be executed. Enter the following at the top of the file to connect to your Bitcoin node:
 
-### Look Up Addresses
+```
+const RpcAgent = require('bcrpc');
+agent = new RpcAgent({port: 18332, user: 'bitcoinrpc', pass: 'd8340efbcd34e312044c8431c59c792c'});
+```
 
-### Look Up Funds
+Now we can start writing programs in JavaScript that access Bitcoind. You can use the same RPC commands you would usually use via ```bitcoin-cli```, except they need to be in camelCase. For example, ```getblockhash``` would be ```getBlockHash``` instead.
+
+### Print the Newest Block
+
+To print the newest block number along with its hash, we can first call ```getBlockCount```, print it, then pass the block number to ```getBlockHash``` and then print the latest hash. Add this code to ```server.js```:
+
+```
+agent.getBlockCount(function (err, blockCount) {
+  if (err)
+    throw Error(JSON.stringify(err));
+  console.log(blockCount.result);
+  agent.getBlockHash(blockCount.result, function (err, hash) {
+    if (err)
+      throw Error(JSON.stringify(err));
+    console.log(hash.result);
+  })
+});
+```
+
+You can run it with ```$ node server.js```. You should get an output similar to this:
+
+```
+1773373
+0000000000000083d29c524d4cfc257adfab8fa9b6f0d207d1d0f1b63e1de11e
+```
+
+## Look Up Your Wallet
+
+You can also lookup your wallet and view your balance, transaction count et cetera:
+
+```
+agent.getWalletInfo(function (err, walletInfo) {
+  if (err)
+    throw Error(JSON.stringify(err));
+  console.log(walletInfo.result);
+});
+```
+
+When you run it, you should get an output similar to this:
+
+```
+{
+  walletname: '',
+  walletversion: 169900,
+  balance: 0.0011,
+  unconfirmed_balance: 0,
+  immature_balance: 0,
+  txcount: 2,
+  keypoololdest: 1591844503,
+  keypoolsize: 999,
+  keypoolsize_hd_internal: 1000,
+  paytxfee: 0,
+  hdseedid: '6b9ccb7d96c45a3ca407a3f3b0e9b42501f05c49',
+  private_keys_enabled: true
+}
+```
+
+Instead of printing all the details associated with your wallet, you can print specific information such as your balance. Since a JSON object is being accessed, this can be done by changing the line ```console.log(walletInfo.result);``` to ```console.log(walletInfo.result.balance);```:
+
+```
+0.0011
+```
 
 ### Create an Address
 
-## Create a Transaction
- 
+We can pass additional arguments to RPC commands as well. Here is an example for generating a new legacy address, with the ```-addresstype``` flag.
+
+```
+agent.getNewAddress('-addresstype', 'legacy', function (err, newAddress) {
+  if (err)
+    throw Error(JSON.stringify(err));
+  console.log(newAddress.result);
+});
+```
+
+Output:
+```
+mtGPcBvRPZFEHo2YX8un9qqPBydhG82uuZ
+```
+
+### List transactions
+
+We can list our previous transactions and view information about transactions such as amount and number of confirmations:
+
+```
+agent.listTransactions(function (err, transactions) {
+  if (err)
+    throw Error(JSON.stringify(err));
+  console.log(transactions.result);
+});
+```
+
+We can also examine a transaction based on its txid:
+
+```
+agent.getTransaction('1661ce322c128e053b8ea8fcc22d17df680d2052983980e2281d692b9b4ab7df', function (err, transaction) {
+  if (err)
+    throw Error(JSON.stringify(err));
+  console.log(transaction.result);
+});
+```
+
+You should get an output similar to this:
+
+```
+{
+  amount: 0.001,
+  confirmations: 4776,
+  blockhash: '000000006628870b0a8a66abea9cf0d4e815c491f079e3fa9e658a87b5dc863a',
+  blockindex: 117,
+  blocktime: 1591857418,
+  txid: '1661ce322c128e053b8ea8fcc22d17df680d2052983980e2281d692b9b4ab7df',
+  walletconflicts: [],
+  time: 1591857343,
+  timereceived: 1591857343,
+  'bip125-replaceable': 'no',
+  details: [
+    {
+      address: 'mpGpCMX6SuUimDZKiVViuhd7EGyVxkNnha',
+      category: 'receive',
+      amount: 0.001,
+      label: '',
+      vout: 0
+    }
+  ],
+  hex: '02000000000101e9e8c3bd057d54e73baadc60c166860163b0e7aa60cab33a03e89fb44321f8d5010000001716001435c2aa3fc09ea53c3e23925c5b2e93b9119b2568feffffff02a0860100000000001976a914600c8c6a4abb0a502ea4de01681fe4fa1ca7800688ac65ec1c000000000017a91425b920efb2fde1a0277d3df11d0fd7249e17cf8587024730440220403a863d312946aae3f3ef0a57206197bc67f71536fb5f4b9ca71a7e226b6dc50220329646cf786cfef79d60de3ef54f702ab1073694022f0618731902d926918c3e012103e6feac9d7a8ad1ac6b36fb4c91c1c9f7fff1e7f63f0340e5253a0e4478b7b13f41fd1a00'
+}
+```
+
+### Get address balance
+
+A useful function when accepting Bitcoin is checking the balance of a specific address in your wallet. For example, if you were running an online store accepting Bitcoin, for each payment from a customer, you would generate a new address (as we did with ```getNewAddress``` function), show that address to the customer, then check the balance of the address after some time, to make sure the correct amount has been received:
+
+```
+agent.getReceivedByAddress('mpGpCMX6SuUimDZKiVViuhd7EGyVxkNnha', function (err, addressInfo) {
+  if (err)
+    throw Error(JSON.stringify(err));
+  console.log(addressInfo.result);
+});
+```
+
+By default this functions checks the transactions that have been confirmed once, however we can increase this to a higher number such as 6:
+
+```
+agent.getReceivedByAddress('mpGpCMX6SuUimDZKiVViuhd7EGyVxkNnha', 6, function (err, addressInfo) {
+  if (err)
+    throw Error(JSON.stringify(err));
+  console.log(addressInfo.result);
+});
+```
+
+Output:
+
+```
+0.0011
+```
+
+## Sending coins
+
+We can send coins to an address using the ```sendToAddress``` function:
+
+```
+agent.sendToAddress('n2eMqTT929pb1RDNuqEnxdaLau1rxy3efi', 0.00001, function(err, txid) {
+  if (err)
+    throw Error(JSON.stringify(err));
+  console.log(txid.result);
+});
+```
+
+This should print the txid of the transaction:
+
+```
+6172d60d154cd4bbb5b6adeaffa191866f3904dd3f525c7a079154aea906b723
+```
+
+We can also use the ```getTransaction``` function to view how many confirmations it has, what fee we paid, et cetera.
+
 ## Summary: Accessing Bitcoind with Node
+
+With BCRPC we can do all the commands available through ```bitcoin-cli```, in JavaScript. Based on these examples you should be able to incorporate Bitcoin in a Node.js project and do things like sending and receiving coins.