lnd.xprv/docs/grpc/javascript.md

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# How to write a simple `lnd` client in Javascript using `node.js`
### Setup and Installation
First, you'll need to initialize a simple nodejs project:
```
npm init (or npm init -f if you want to use the default values without prompt)
```
Then you need to install the Javascript grpc library dependency:
```
npm install grpc --save
```
You also need to copy the `lnd` `rpc.proto` file in your project directory (or
at least somewhere reachable by your Javascript code).
The `rpc.proto` file is [located in the `lnrpc` directory of the `lnd`
sources](https://github.com/lightningnetwork/lnd/blob/master/lnrpc/rpc.proto).
In order for the auto-generated code to compile successfully, you'll need to
comment out the following line:
```
//import "google/api/annotations.proto";
```
#### Imports and Client
Every time you work with Javascript gRPC, you will have to import `grpc`, load
`rpc.proto`, and create a connection to your client like so:
```js
var grpc = require('grpc');
var fs = require("fs");
// Due to updated ECDSA generated tls.cert we need to let gprc know that
// we need to use that cipher suite otherwise there will be a handhsake
// error when we communicate with the lnd rpc server.
process.env.GRPC_SSL_CIPHER_SUITES = 'HIGH+ECDSA'
// Lnd cert is at ~/.lnd/tls.cert on Linux and
// ~/Library/Application Support/Lnd/tls.cert on Mac
var lndCert = fs.readFileSync("~/.lnd/tls.cert");
var credentials = grpc.credentials.createSsl(lndCert);
var lnrpcDescriptor = grpc.load("rpc.proto");
var lnrpc = lnrpcDescriptor.lnrpc;
var lightning = new lnrpc.Lightning('localhost:10009', credentials);
```
### Examples
Let's walk through some examples of Javascript gRPC clients. These examples
assume that you have at least two `lnd` nodes running, the RPC location of one
of which is at the default `localhost:10009`, with an open channel between the
two nodes.
#### Simple RPC
```js
> lightning.getInfo({}, function(err, response) {
console.log('GetInfo:', response);
});
```
You should get something like this in your console:
```
GetInfo: { identity_pubkey: '03c892e3f3f077ea1e381c081abb36491a2502bc43ed37ffb82e264224f325ff27',
alias: '',
num_pending_channels: 0,
num_active_channels: 1,
num_peers: 1,
block_height: 1006,
block_hash: '198ba1dc43b4190e507fa5c7aea07a74ec0009a9ab308e1736dbdab5c767ff8e',
synced_to_chain: false,
testnet: false,
chains: [ 'bitcoin' ] }
```
#### Response-streaming RPC
```js
var call = lightning.subscribeInvoices({});
call.on('data', function(invoice) {
console.log(invoice);
})
.on('end', function() {
// The server has finished sending
})
.on('status', function(status) {
// Process status
console.log("Current status" + status);
});
```
Now, create an invoice for your node at `localhost:10009`and send a payment to
it from another node.
```bash
$ lncli addinvoice --amt=100
{
"r_hash": <RHASH>,
"pay_req": <PAYMENT_REQUEST>
}
$ lncli sendpayment --pay_req=<PAYMENT_REQUEST>
```
Your Javascript console should now display the details of the recently satisfied
invoice.
#### Bidirectional-streaming RPC
This example has a few dependencies:
```shell
npm install --save async lodash bytebuffer
```
You can run the following in your shell or put it in a program and run it like
`node script.js`
```js
// Load some libraries specific to this example
var async = require('async');
var _ = require('lodash');
var ByteBuffer = require('bytebuffer');
var dest_pubkey = <RECEIVER_ID_PUBKEY>;
var dest_pubkey_bytes = ByteBuffer.fromHex(dest_pubkey);
// Set a listener on the bidirectional stream
var call = lightning.sendPayment();
call.on('data', function(payment) {
console.log("Payment sent:");
console.log(payment);
});
call.on('end', function() {
// The server has finished
console.log("END");
});
// You can send single payments like this
call.write({ dest: dest_pubkey_bytes, amt: 6969 });
// Or send a bunch of them like this
function paymentSender(destination, amount) {
return function(callback) {
console.log("Sending " + amount + " satoshis");
console.log("To: " + destination);
call.write({
dest: destination,
amt: amount
});
_.delay(callback, 2000);
};
}
var payment_senders = [];
for (var i = 0; i < 10; i++) {
payment_senders[i] = paymentSender(dest_pubkey_bytes, 100);
}
async.series(payment_senders, function() {
call.end();
});
```
This example will send a payment of 100 satoshis every 2 seconds.
#### Using Macaroons
To authenticate using macaroons you need to include the macaroon in the metadata of the request.
```js
var fs = require('fs');
var grpc = require('grpc');
process.env.GRPC_SSL_CIPHER_SUITES = 'HIGH+ECDSA'
// Lnd admin macaroon is at ~/.lnd/admin.macaroon on Linux and
// ~/Library/Application Support/Lnd/admin.macaroon on Mac
var m = fs.readFileSync('~/.lnd/admin.macaroon');
var macaroon = m.toString('hex');
var meta = new grpc.Metadata().add('macaroon', macaroon);
var lnrpcDescriptor = grpc.load("rpc.proto");
var lnrpc = lnrpcDescriptor.lnrpc;
var client = new lnrpc.Lightning('some.address:10009', grpc.credentials.createInsecure());
client.getInfo({}, meta);
```
However, this can get tiresome to do for each request, so to avoid explicitly including the macaroon we can update the credentials to include it automatically.
```js
var fs = require('fs');
var grpc = require('grpc');
process.env.GRPC_SSL_CIPHER_SUITES = 'HIGH+ECDSA'
// Lnd admin macaroon is at ~/.lnd/admin.macaroon on Linux and
// ~/Library/Application Support/Lnd/admin.macaroon on Mac
var m = fs.readFileSync('~/.lnd/admin.macaroon');
var macaroon = m.toString('hex');
// build meta data credentials
var metadata = new grpc.Metadata().add('macaroon', macaroon)
var macaroonCreds = grpc.credentials.createFromMetadataGenerator((_args, callback) => {
callback(null, metadata);
});
// build ssl credentials using the cert the same as before
var lndCert = fs.readFileSync("~/.lnd/tls.cert");
var sslCreds = grpc.credentials.createSsl(lndCert);
// combine the cert credentials and the macaroon auth credentials
// such that every call is properly encrypted and authenticated
var credentials = grpc.credentials.combineChannelCredentials(sslCreds, macaroonCreds);
// Pass the crendentials when creating a channel
var lnrpcDescriptor = grpc.load("rpc.proto");
var lnrpc = lnrpcDescriptor.lnrpc;
var client = new lnrpc.Lightning('some.address:10009', credentials);
client.getInfo({}, (err, res) => { ... });
```
### Conclusion
With the above, you should have all the `lnd` related `gRPC` dependencies
installed locally in your project. In order to get up to speed with `protofbuf`
usage from Javascript, see [this official `protobuf` reference for
Javascript](https://developers.google.com/protocol-buffers/docs/reference/javascript-generated).
Additionally, [this official gRPC
resource](http://www.grpc.io/docs/tutorials/basic/node.html) provides more
details around how to drive `gRPC` from `node.js`.