Send heartbeat to bitcoinity to keep the connection alive

Thanks to blueagain for figuring this out.
This allows for long queries to bitcoinity to not fail
when the requested exchange/currency pair is not received
quickly enough

docs/bitcoinity/reference_implementation.js

@@ -0,0 +1,32 @@
+// Copyright 2022, blueagain
+// https://github.com/terrablue
+
+import WebSocket from "ws";
+
+const ws = new WebSocket("ws://bitcoinity.org/webs_bridge/websocket");
+let ref = 2;
+const send = (ws, data) => {
+  ws.send(JSON.stringify({...data, payload: {}, ref}));
+  ref++;
+}
+
+const join = (ws, topic) =>
+  send(ws, {topic, event: "phx_join"});
+
+const currencies = ["USD"];
+
+ws.on("open", () => {
+  ws.on("message", message => {
+    const parsed_message = JSON.parse(message);
+    if (currencies.includes(parsed_message.payload.data?.currency)) {
+      const {currency, exchange_name, last} = parsed_message.payload.data;
+      console.log(`currency: ${currency}, exchange: ${exchange_name}, last: ${last}`);
+    }
+
+  });
+  join(ws, "webs:markets");
+  join(ws, "webs:bitfinex_USD");
+  setInterval(() => {
+    send(ws, {topic: "phoenix", event: "heartbeat"})
+  }, 30000)
+})