XRPL WebSocket Client  

🚨 WARNING! 🚨 If you are using xrpl-client in a serverless environment, make sure to .close() your connection at the end, to prevent your connection to linger on for a long time (causing massive load on public infrastructure, and massive serverless function invocation time bills from your cloud provider!)

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Auto reconnecting, buffering, subscription remembering XRP Ledger WebSocket client. For in node & the browser.

This client implements a check for a working XRPL connection: the WebSocket being simply online isn't enough to satisfy the online / offline detection of this lib. After connecting, this lib. will issue a server_info command to the other connected node. Only if a valid response is retrieved the connection will be marked as online.

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You can clone this repository and run:

- npm run install to install dependencies
- npm run build to build the source code
- npm run browserify to browserify this lib.

Now the dist/browser.js file will exist, for you to use in a browser.

You can get a prebuilt / prebuilt & minified version from Github / CDNJS  

Sample: https://jsfiddle.net/WietseWind/p4cd37hf

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Please note: this lib only provides connectivity to XRPL nodes. To sign transactions, please take a look at xrpl-accountlib. Here's an example on how these two libs can work together:
https://gist.github.com/WietseWind/557a5c11fa0d474468e8c9c54e3e5b93

#### Constructor & options

A client connection can be constructed with the exported XrplClient class:

``typescript
import { XrplClient } from "xrpl-client";
const client = new XrplClient();
// ^^ No arguments: defaults to one endpoint:
// ['wss://xrplcluster.com', 'wss://xrpl.link', 'wss://s2.ripple.com']
// with maxConnectionAttempts option null (= try forever)
`

If no argument is provided, the default endpoint this lib. will connect to is wss://xrplcluster.com, wss://xrpl.link (fallback) and finally wss://s2.ripple.com. Alternatively, two arguments can be provided:

###### Arguments

1. (string | array) The WebSocket endpoint to connect to (e.g. your own node) as a string, or an array (string[]) with multiple endpoints used in specified order. Empty string or array if you want to use the default nodes, but specify custom options using the second param.:
2. (object) Global options (type: WsClientOptions)

###### Options

Available options are:

- assumeOfflineAfterSeconds, Number » default 15, this setting will check if the XRPL node on the other end of the connection is alive and sending regular server_info responses (this lib. queries for them). After the timeout, the lib. will disconnect from the node and try to reconnect.
- maxConnectionAttempts, Number | null » default null in case of one endpoint, or 3 if an array with endpoints is provided, if (when initially connecting or reconnecting) no (new) connection could be setup in this attempts (see: connectAttemptTimeoutSeconds per call) consider the connection dead. Cancel all connect/reconnect attempts, clear the command buffer. An error will be thrown.
- connectAttemptTimeoutSeconds, Number » default 3, this setting is the max. delay between reconnect attempts, if no connection could be setup to the XRPL node. A backoff starting at one second, growing with 20% per attempt until this value is reached will be used.
- feeDropsDefault, Number » default 12, The min. amount of node reported transaction fee (in drops) respected for the getState() reported last/avg fee amount.
- feeDropsMax, Number » default 3600, The max. amount of node reported transaction fee (in drops) respected for the getState() reported last/avg fee amount.
- tryAllNodes, Boolean » default false, If connection attempts will be made to all nodes at the same time, connecting the client to the first to respond.

Sample with a custom node & option:

`typescript
import { XrplClient } from "xrpl-client";
const client = new XrplClient(
["ws://localhost:1337", "wss://xrplcluster.com"],
{
assumeOfflineAfterSeconds: 15,
maxConnectionAttempts: 4,
connectAttemptTimeoutSeconds: 4,
}
);
`

#### Methods:

- send({ command: "..."}, {SendOptions}) » Promise » Send a command to the connected XRPL node.
- ready() » Promise » fires when you're fully connected. While the state event (and getState() method) only return the WebSocket online state, ready() will only return (async) if the first ledger data has been received and the last ledger index is known.
- getState() » ConnectionState » Get the connection, connectivity & server state (e.g. fees, reserves).
- close() » void » Close the connection, but allow the object to be used again (using reinstate()).
- reinstate(options?: {forceNextUplink: boolean}) » void » Reconnect the object when in closed state (after calling close()). By passing forceNextUplink: true (default false) the connection will be reinstated to the next uplink instead of starting again from the first provided uplink (constructor). If the Client class was constructed with the tryAllNodes: true option, there is no "next uplink", as all will be tried. In which case the forceNextUplink: true option will be ignored.
- destroy() » void » Fully close the entire object (can't be used again).

#### Send options

The send({ command: "..." }) method allows you to set these options (second argument, object):

- timeoutSeconds, Number » The returned Promise will be rejected if a response hasn't been received within this amount of seconds. This timeout starts when the command is issued by your code, no matter the connection state (online or offline, possibly waiting for a connecftion)
- timeoutStartsWhenOnline, Number » The timeout (see timeoutSeconds) will start when the connection has been marked online (WebSocket connected, server_info received from the XRPL node), so when your command has been issued by this lib. to the XRPL node on the other end of the connection.
- sendIfNotReady, Boolean » Your commands will be sent to the XRPL node on the other end of the connection only when the connection has been marked online (WebSocket connected, server_info received from the XRPL node). Adding this option (true) will send your commands _after_ the WebSocket has been connected, but possibly _before_ a valid server_info response has been received by the XRPL node connected to.
- noReplayAfterReconnect, Boolean » When adding a subscription (resulting in async. updates) like a subscribe or path_find command, when reconnected your subscription commands will automaticaly replay to the newly connected node. Providing a false to this option will prevent your commands from being replayed when reconnected.

#### Events emitted:

- state (the state of the connection changed from online to offline or vice versa)
- message (all messages, even if duplicate of the ones below)
- ledger (a ledger closed)
- path (async path_find response)
- transaction
- validation
- retry (new connection attempt)
- close (upstream closed the connection)
- reconnect (reconnecting, after connected: state)

#### Connection flow events:

- retry - Same node, new connection attempt (attempt timed out)
- nodeswitch » string (node) - Switched to a new node
- online » Now conneted to an XRPL node, use .getState() for more info
- offline » Was online, but the connection is gone
- round » Tried all nodes, retry the first one

Let's say you have two dead endpoints and a third one that works, then your connection is lost and you switch to the fourth one. The event sequence would look like this:

`
1. retry » 2. retry » 3. retry » 4. nodeswitch
5. retry » 6. retry » 7. retry » 8. nodeswitch
9. online
10. offline
11. retry » 12. retry » 13. retry » 14. nodeswitch
15. online
`

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`typescript
import { XrplClient } from "xrpl-client";
const client = new XrplClient("wss://xrplcluster.com");

// await client.ready();

const serverInfo = await client.send({ command: "server_info" });
console.log({ serverInfo });

client.on("ledger", (ledger) => {
console.log("Ledger", ledger);
});
`

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1. The constructor doesn't return a promise with the connection: the constructed object passes on your messages. So if you need to wait for a live connection: use await TheObject.ready() and then refer to TheObject:

`javascript
// Old:
// new RippledWsClient('wss://testnet.xrpl-labs.com').then(Connection => { ... })
// New:
const Connection = new RippledWsClient('wss://testnet.xrpl-labs.com')
Connection.ready().then(() => {
`

3. When used in combination with rippled-ws-client-sign (please use xrpl-accountlib instead!) you need to wrap the class:

`javascript
class RippledWsClient extends XrplClient {} // Then use RippledWsClient
`

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You can configure your own proxy-enabled http.Agent and pass it as option:

`
import { HttpsProxyAgent } from "https-proxy-agent";

const agent = new HttpsProxyAgent({
host: "proxy.corporate.lan",
port: 3128,
});

const client = new XrplClient("wss://xrplcluster.com", {
httpRequestOptions: { agent },
});
`

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To see all debugging info, run the compiled version with the DEBUG env. var:

`bash
tsc
DEBUG=xrplclient* node someFile.js
``