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# 18.1: Accessing Bitcoind with NodeJS
## Set up Go
First, install curl if you haven't already:
```
$ sudo apt install curl
```
Then, look at the [Go downloads page](https://golang.org/dl/) and get the link for the latest download:
```
$ curl -O https://dl.google.com/go/go1.14.4.linux-amd64.tar.gz
```
Once it finishes downloading, compare the hash of the download to the hash on the [Go downloads page](https://golang.org/dl/):
```
$ sha256sum go1.14.4.linux-amd64.tar.gz
aed845e4185a0b2a3c3d5e1d0a35491702c55889192bb9c30e67a3de6849c067 /home/user1/go1.14.4.linux-amd64.tar.gz
```
The hashes should match. Now we can extract the tarball and install Go on our system:
```
$ tar xvf go1.12.5.linux-amd64.tar.gz
$ sudo chown -R root:root ./go
$ sudo mv go /usr/local
```
Now we need to create a Go path to specify our environment. Open the ```~/.profile``` file with an editor of your choice and add the following to the end of it:
```
export GOPATH=$HOME/work
export PATH=$PATH:/usr/local/go/bin:$GOPATH/bin
```
Then, refresh your profile:
```
$ source ~/.profile
```
Lastly, create the directory for your Go workspace:
```
$ mkdir $HOME/work
```
## Setup btcd rpcclient
We will be using the rpcclient that comes with btcd, a Bitcoin implementation written in Go. We can use ```go get``` to download it:
```
$ go get github.com/btcsuite/btcd/rpcclient
```
To test that it works, navigate to the directory with the Bitcoin core examples:
```
$ cd $GOPATH/src/github.com/btcsuite/btcd/rpcclient/examples/bitcoincorehttp
```
Modify the ```main.go``` file and enter the details associated with your Bitcoin core setup:
```
Host: "localhost:18332",
User: "bitcoinrpc",
Pass: "d8340efbcd34e312044c8431c59c792c",
```
Now run:
```
$ go run main.go
```
You should see the block count printed:
```
2020/06/24 20:41:01 Block count: 1773552
```
### Print the latest block
Leave the btcd directory and create a new Go project:
```
$ mkdir -p ~/work/src/myproject/bitcoin
$ cd ~/work/src/myproject/bitcoin
```
In this directory, create a file called ```main.go``` and enter the following in it:
```
package main
import (
"log"
"fmt"
"github.com/btcsuite/btcd/rpcclient"
)
func main() {
connCfg := &rpcclient.ConnConfig{
Host: "localhost:18332",
User: "bitcoinrpc",
Pass: "431451790e3eee1913115b9dd2fbf0ac",
HTTPPostMode: true,
DisableTLS: true,
}
client, err := rpcclient.New(connCfg, nil)
if err != nil {
log.Fatal(err)
}
defer client.Shutdown()
blockCount, err := client.GetBlockCount()
if err != nil {
log.Fatal(err)
}
blockHash, err := client.GetBlockHash(blockCount)
if err != nil {
log.Fatal(err)
}
fmt.Printf("%d\n", blockCount)
fmt.Printf("%s\n", blockHash.String())
}
```
Make sure to change your username and password to those from your ```~/.bitcoin/bitcoin.conf``` file. When you run this:
```
$ go run main.go
1773561
00000000000000346bab4126f418a5820692c9a7de7ef79717bebfccebacad61
```
The latest block number along with its hash should be printed out.
### Getting your wallet balance
Since the btcd rpcclient is quite limited, we can't make a use the ```getwalletinfo``` functino, however we can get the balance of our wallet:
```
package main
import (
"log"
"fmt"
"github.com/btcsuite/btcd/rpcclient"
)
func main() {
connCfg := &rpcclient.ConnConfig{
Host: "localhost:18332",
User: "bitcoinrpc",
Pass: "431451790e3eee1913115b9dd2fbf0ac",
HTTPPostMode: true,
DisableTLS: true,
}
client, err := rpcclient.New(connCfg, nil)
if err != nil {
log.Fatal(err)
}
defer client.Shutdown()
wallet, err := client.GetBalance("*")
if err != nil {
log.Fatal(err)
}
fmt.Println(wallet)
}
```
You should get an output similar to this:
```
0.000689 BTC
```
### Get amount received by an address
We can retrieve the amount of Bitcoin received by a specific address:
```
package main
import (
"log"
"fmt"
"github.com/btcsuite/btcd/rpcclient"
"github.com/btcsuite/btcutil"
"github.com/btcsuite/btcd/chaincfg"
)
func main() {
connCfg := &rpcclient.ConnConfig{
Host: "localhost:18332",
User: "bitcoinrpc",
Pass: "431451790e3eee1913115b9dd2fbf0ac",
HTTPPostMode: true,
DisableTLS: true,
}
client, err := rpcclient.New(connCfg, nil)
if err != nil {
log.Fatal(err)
}
defer client.Shutdown()
defaultNet := &chaincfg.TestNet3Params
addr, err := btcutil.DecodeAddress("mpGpCMX6SuUimDZKiVViuhd7EGyVxkNnha", defaultNet)
if err != nil {
log.Fatal(err)
}
wallet, err := client.GetReceivedByAddress(addr)
fmt.Println(wallet)
}
```
The defaultNet variable is used to specify whether our Bitcoin node is on testnet or on mainnet.
### Sending Bitcoin to an address
```
package main
import (
"log"
"fmt"
"github.com/btcsuite/btcd/rpcclient"
"github.com/btcsuite/btcutil"
"github.com/btcsuite/btcd/chaincfg"
)
func main() {
connCfg := &rpcclient.ConnConfig{
Host: "localhost:18332",
User: "bitcoinrpc",
Pass: "431451790e3eee1913115b9dd2fbf0ac",
HTTPPostMode: true,
DisableTLS: true,
}
client, err := rpcclient.New(connCfg, nil)
if err != nil {
log.Fatal(err)
}
defer client.Shutdown()
defaultNet := &chaincfg.TestNet3Params
addr, err := btcutil.DecodeAddress("n2eMqTT929pb1RDNuqEnxdaLau1rxy3efi", defaultNet)
if err != nil {
log.Fatal(err)
}
sent, err := client.SendToAddress(addr, btcutil.Amount(1e4))
if err != nil {
log.Fatal(err)
}
fmt.Println(sent)
}
```
This outputs the txid of the transaction.
### Lookup a transaction
```
package main
import (
"log"
"fmt"
"github.com/btcsuite/btcd/rpcclient"
"github.com/btcsuite/btcd/chaincfg/chainhash"
)
func main() {
connCfg := &rpcclient.ConnConfig{
Host: "localhost:18332",
User: "bitcoinrpc",
Pass: "431451790e3eee1913115b9dd2fbf0ac",
HTTPPostMode: true,
DisableTLS: true,
}
client, err := rpcclient.New(connCfg, nil)
if err != nil {
log.Fatal(err)
}
defer client.Shutdown()
chash, err := chainhash.NewHashFromStr("1661ce322c128e053b8ea8fcc22d17df680d2052983980e2281d692b9b4ab7df")
if err != nil {
log.Fatal(err)
}
transactions, err := client.GetTransaction(chash)
if err != nil {
log.Fatal(err)
}
fmt.Println(transactions)
}
```
This prints out the details associated with a transaction, such as its amount and how many times it has been confirmed:
```
{
"amount": 0.00100000,
"confirmations": 4817,
"blockhash": "000000006628870b0a8a66abea9cf0d4e815c491f079e3fa9e658a87b5dc863a",
"blockindex": 117,
"blocktime": 1591857418,
"txid": "1661ce322c128e053b8ea8fcc22d17df680d2052983980e2281d692b9b4ab7df",
"walletconflicts": [
],
"time": 1591857343,
"timereceived": 1591857343,
"bip125-replaceable": "no",
"details": [
{
"address": "mpGpCMX6SuUimDZKiVViuhd7EGyVxkNnha",
"category": "receive",
"amount": 0.00100000,
"label": "",
"vout": 0
}
],
"hex": "02000000000101e9e8c3bd057d54e73baadc60c166860163b0e7aa60cab33a03e89fb44321f8d5010000001716001435c2aa3fc09ea53c3e23925c5b2e93b9119b2568feffffff02a0860100000000001976a914600c8c6a4abb0a502ea4de01681fe4fa1ca7800688ac65ec1c000000000017a91425b920efb2fde1a0277d3df11d0fd7249e17cf8587024730440220403a863d312946aae3f3ef0a57206197bc67f71536fb5f4b9ca71a7e226b6dc50220329646cf786cfef79d60de3ef54f702ab1073694022f0618731902d926918c3e012103e6feac9d7a8ad1ac6b36fb4c91c1c9f7fff1e7f63f0340e5253a0e4478b7b13f41fd1a00"
}
```
## Summary: Accessing Bitcoind with Node
Although the btcd rpcclient is quite limited, we can still perform a lot of the main rpc commands in Go.

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}
```
### Get address balance
### Get Amount Received by an Address
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:
A useful function when accepting Bitcoin is checking the received Bitcoin 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) {

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@ -104,9 +104,9 @@ _This section is currently a messy set of older writings which are being reorgan
* 17.4: Integrating Libwally and Scripts
* 17.0: Talking to Lightningd with C
* 18.0: Talking to Bitcoind with Other Languages
* [18.1: Accessing Bitcoind with Go]
* [18.1: Accessing Bitcoind with Go](18_1_Accessing_Bitcoind_with_Go.md)
* [18.2: Accessing Bitcoind with Java](18_2_Accessing_Bitcoind_with_Java.md) — Needs Rewrite + Editing
* [18.3: Accessing Bitcoind with Node JS](18_3_Accessing_Bitcoind_with_NodeJS.md) — Needs Rewrite + Editing
* [18.3: Accessing Bitcoind with Node JS](18_3_Accessing_Bitcoind_with_NodeJS.md)
* [18.4: Accessing Bitcoind with Python]
* [18.5: Accessing Bitcoind with Rust]
* [18.6: Accessing Bitcoind with Swift]