MessagePack (Node)

Opt a connection into MessagePack for lower bandwidth on high-volume channels. Two rules: (a) everything after your set_format, starting with the format_set confirmation itself, arrives as binary MessagePack, so flip your decoder the moment you send the request (b) switch while the socket is quiet (right after connect, before subscribing). You can keep sending plain JSON text, the server decodes text as JSON and binary as MessagePack independently of the outbound format.

import WebSocket from "ws";                  // npm i ws

import { decode } from "@msgpack/msgpack";   // npm i @msgpack/msgpack

const ws = new WebSocket("wss://api.archer.exchange/v1/stream");

let msgpack = false;

ws.on("open", () => {

  // Switch first, before any subscribe, while the connection is quiet.

  ws.send(JSON.stringify({ op: "set_format", format: "msgpack" }));

  msgpack = true; // every inbound frame from here on is binary msgpack

  ws.send(JSON.stringify({ op: "subscribe", channels: ["orderbook"], market: "5Ggx..." }));

  setInterval(() => ws.send(JSON.stringify({ op: "ping", ts: Date.now() })), 30_000);

});

ws.on("message", (data, isBinary) => {

  // data is a Buffer. Decode as msgpack once switched; JSON before that.

  const msg = (msgpack || isBinary) ? decode(data) : JSON.parse(data.toString());

  if (msg.op === "format_set") console.log("format is now", msg.format); // arrives already msgpack-encoded

  else if (msg.op) console.log("op:", msg.op);

  else console.log("ch:", msg.ch, msg.type);

});

Transaction relay

Tutorials

Client examples