engine.io-client/lib/transports/websocket.js

Client for the realtime Engine

const Transport = require("../transport");
const parser = require("engine.io-parser");
const parseqs = require("parseqs");
const yeast = require("yeast");
const { pick } = require("../util");
const {
  WebSocket,
  usingBrowserWebSocket,
  defaultBinaryType,
  nextTick
} = require("./websocket-constructor");

const debug = require("debug")("engine.io-client:websocket");

// detect ReactNative environment
const isReactNative =
  typeof navigator !== "undefined" &&
  typeof navigator.product === "string" &&
  navigator.product.toLowerCase() === "reactnative";

class WS extends Transport {
  /**
   * WebSocket transport constructor.
   *
   * @api {Object} connection options
   * @api public
   */
  constructor(opts) {
    super(opts);

    this.supportsBinary = !opts.forceBase64;
  }

  /**
   * Transport name.
   *
   * @api public
   */
  get name() {
    return "websocket";
  }

  /**
   * Opens socket.
   *
   * @api private
   */
  doOpen() {
    if (!this.check()) {
      // let probe timeout
      return;
    }

    const uri = this.uri();
    const protocols = this.opts.protocols;

    // React Native only supports the 'headers' option, and will print a warning if anything else is passed
    const opts = isReactNative
      ? {}
      : pick(
          this.opts,
          "agent",
          "perMessageDeflate",
          "pfx",
          "key",
          "passphrase",
          "cert",
          "ca",
          "ciphers",
          "rejectUnauthorized",
          "localAddress",
          "protocolVersion",
          "origin",
          "maxPayload",
          "family",
          "checkServerIdentity"
        );

    if (this.opts.extraHeaders) {
      opts.headers = this.opts.extraHeaders;
    }

    try {
      this.ws =
        usingBrowserWebSocket && !isReactNative
          ? protocols
            ? new WebSocket(uri, protocols)
            : new WebSocket(uri)
          : new WebSocket(uri, protocols, opts);
    } catch (err) {
      return this.emit("error", err);
    }

    this.ws.binaryType = this.socket.binaryType || defaultBinaryType;

    this.addEventListeners();
  }

  /**
   * Adds event listeners to the socket
   *
   * @api private
   */
  addEventListeners() {
    this.ws.onopen = () => {
      if (this.opts.autoUnref) {
        this.ws._socket.unref();
      }
      this.onOpen();
    };
    this.ws.onclose = this.onClose.bind(this);
    this.ws.onmessage = ev => this.onData(ev.data);
    this.ws.onerror = e => this.onError("websocket error", e);
  }

  /**
   * Writes data to socket.
   *
   * @param {Array} array of packets.
   * @api private
   */
  write(packets) {
    this.writable = false;

    // encodePacket efficient as it uses WS framing
    // no need for encodePayload
    for (let i = 0; i < packets.length; i++) {
      const packet = packets[i];
      const lastPacket = i === packets.length - 1;

      parser.encodePacket(packet, this.supportsBinary, data => {
        // always create a new object (GH-437)
        const opts = {};
        if (!usingBrowserWebSocket) {
          if (packet.options) {
            opts.compress = packet.options.compress;
          }

          if (this.opts.perMessageDeflate) {
            const len =
              "string" === typeof data ? Buffer.byteLength(data) : data.length;
            if (len < this.opts.perMessageDeflate.threshold) {
              opts.compress = false;
            }
          }
        }

        // Sometimes the websocket has already been closed but the browser didn't
        // have a chance of informing us about it yet, in that case send will
        // throw an error
        try {
          if (usingBrowserWebSocket) {
            // TypeError is thrown when passing the second argument on Safari
            this.ws.send(data);
          } else {
            this.ws.send(data, opts);
          }
        } catch (e) {
          debug("websocket closed before onclose event");
        }

        if (lastPacket) {
          // fake drain
          // defer to next tick to allow Socket to clear writeBuffer
          nextTick(() => {
            this.writable = true;
            this.emit("drain");
          });
        }
      });
    }
  }

  /**
   * Called upon close
   *
   * @api private
   */
  onClose() {
    Transport.prototype.onClose.call(this);
  }

  /**
   * Closes socket.
   *
   * @api private
   */
  doClose() {
    if (typeof this.ws !== "undefined") {
      this.ws.close();
      this.ws = null;
    }
  }

  /**
   * Generates uri for connection.
   *
   * @api private
   */
  uri() {
    let query = this.query || {};
    const schema = this.opts.secure ? "wss" : "ws";
    let port = "";

    // avoid port if default for schema
    if (
      this.opts.port &&
      (("wss" === schema && Number(this.opts.port) !== 443) ||
        ("ws" === schema && Number(this.opts.port) !== 80))
    ) {
      port = ":" + this.opts.port;
    }

    // append timestamp to URI
    if (this.opts.timestampRequests) {
      query[this.opts.timestampParam] = yeast();
    }

    // communicate binary support capabilities
    if (!this.supportsBinary) {
      query.b64 = 1;
    }

    query = parseqs.encode(query);

    // prepend ? to query
    if (query.length) {
      query = "?" + query;
    }

    const ipv6 = this.opts.hostname.indexOf(":") !== -1;
    return (
      schema +
      "://" +
      (ipv6 ? "[" + this.opts.hostname + "]" : this.opts.hostname) +
      port +
      this.opts.path +
      query
    );
  }

  /**
   * Feature detection for WebSocket.
   *
   * @return {Boolean} whether this transport is available.
   * @api public
   */
  check() {
    return (
      !!WebSocket &&
      !("__initialize" in WebSocket && this.name === WS.prototype.name)
    );
  }
}

module.exports = WS;