minisocket.js

var crypto = require("crypto");
var KEY_SUFFIX = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";

function hashWebSocketKey(key) {
    var sha1 = crypto.createHash("sha1");
    sha1.update(key + KEY_SUFFIX, "ascii");
    return sha1.digest("base64");
}

/**
 * Limitations: the current implementation does not 
 * care about what the client send:
 * - we don't know `ws.close` only know `socket.closed` which is later so it has a latency
 * - ping pong protocol
 */
// http://tools.ietf.org/html/rfc6455#section-5.2
var opcodes = {
    TEXT: 1,
    BINARY: 2,
    CLOSE: 8,
    PING: 9,
    PONG: 10
};

/**
 * 
 * @param {number} opcode 
 * @param {Buffer} payload 
 */
function encodeMessage(opcode, payload) {
    var buf; // Buffer type
    var b1 = 0x80 | opcode;
    // always send message as one frame (fin)

    // second byte: maks and length part 1
    // followed by 0, 2, or 8 additional bytes of continued length
    var b2 = 0;
    // server does not mask frames
    var length = payload.length;
    if (length < 126) {
        buf = Buffer.allocUnsafe(payload.length + 2 + 0);
        // zero extra bytes
        b2 |= length;
        buf.writeUInt8(b1, 0);
        buf.writeUInt8(b2, 1);
        payload.copy(buf, 2);
    } else if (length < (1 << 16)) {
        buf = Buffer.allocUnsafe(payload.length + 2 + 2);
        // two bytes extra
        b2 |= 126;
        buf.writeUInt8(b1, 0);
        buf.writeUInt8(b2, 1);
        // add two byte length
        buf.writeUInt16BE(length, 2);
        payload.copy(buf, 4);
    } else {
        buf = Buffer.allocUnsafe(payload.length + 2 + 8);
        // eight bytes extra
        b2 |= 127;
        buf.writeUInt8(b1, 0);
        buf.writeUInt8(b2, 1);
        // add eight byte length
        // note: this implementation cannot handle lengths greater than 2^32
        // the 32 bit length is prefixed with 0x0000
        buf.writeUInt32BE(0, 2);
        buf.writeUInt32BE(length, 6);
        payload.copy(buf, 10);
    }
    return buf;
};

var upgradeHeader = 'HTTP/1.1 101 Web Socket Protocol Handshake\r\nUpgrade: WebSocket\r\nConnection: Upgrade\r\nsec-websocket-accept: '
class MiniWebSocket  {
    constructor(req, socket, upgradeHead) {
        this.socket = socket;
        this.closed = false;
        var self = this;
        var key = hashWebSocketKey(req.headers["sec-websocket-key"])

        // http://tools.ietf.org/html/rfc6455#section-4.2.2
        socket.write( upgradeHeader + key + '\r\n\r\n');
        socket.on("close", function (hadError) {
            if (!self.closed) {
                self.closed = true;
            }
        });
    };
    sendText(obj) {
        this.socket.write(encodeMessage(opcodes.TEXT,Buffer.from(obj, "utf8")))
    };
}
exports.MiniWebSocket = MiniWebSocket