WebSocketConnection.js

/************************************************************************
 *  Copyright 2010-2015 Brian McKelvey.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 ***********************************************************************/

var util = require('util');
var utils = require('./utils');
var EventEmitter = require('events').EventEmitter;
var WebSocketFrame = require('./WebSocketFrame');
var BufferList = require('../vendor/FastBufferList');
var Validation = require('./Validation').Validation;
var bufferAllocUnsafe = utils.bufferAllocUnsafe;
var bufferFromString = utils.bufferFromString;

// Connected, fully-open, ready to send and receive frames
const STATE_OPEN = 'open';
// Received a close frame from the remote peer
const STATE_PEER_REQUESTED_CLOSE = 'peer_requested_close';
// Sent close frame to remote peer.  No further data can be sent.
const STATE_ENDING = 'ending';
// Connection is fully closed.  No further data can be sent or received.
const STATE_CLOSED = 'closed';

var setImmediateImpl = ('setImmediate' in global) ?
                            global.setImmediate.bind(global) :
                            process.nextTick.bind(process);

var idCounter = 0;

function WebSocketConnection(socket, extensions, protocol, maskOutgoingPackets, config) {
    this._debug = utils.BufferingLogger('websocket:connection', ++idCounter);
    this._debug('constructor');
    
    if (this._debug.enabled) {
        instrumentSocketForDebugging(this, socket);
    }
    
    // Superclass Constructor
    EventEmitter.call(this);

    this._pingListenerCount = 0;
    this.on('newListener', function(ev) {
        if (ev === 'ping'){
            this._pingListenerCount++;
        }
      }).on('removeListener', function(ev) {
        if (ev === 'ping') {
            this._pingListenerCount--;
        }
    });

    this.config = config;
    this.socket = socket;
    this.protocol = protocol;
    this.extensions = extensions;
    this.remoteAddress = socket.remoteAddress;
    this.closeReasonCode = -1;
    this.closeDescription = null;
    this.closeEventEmitted = false;

    // We have to mask outgoing packets if we're acting as a WebSocket client.
    this.maskOutgoingPackets = maskOutgoingPackets;

    // We re-use the same buffers for the mask and frame header for all frames
    // received on each connection to avoid a small memory allocation for each
    // frame.
    this.maskBytes = bufferAllocUnsafe(4);
    this.frameHeader = bufferAllocUnsafe(10);

    // the BufferList will handle the data streaming in
    this.bufferList = new BufferList();

    // Prepare for receiving first frame
    this.currentFrame = new WebSocketFrame(this.maskBytes, this.frameHeader, this.config);
    this.fragmentationSize = 0; // data received so far...
    this.frameQueue = [];
    
    // Various bits of connection state
    this.connected = true;
    this.state = STATE_OPEN;
    this.waitingForCloseResponse = false;
    // Received TCP FIN, socket's readable stream is finished.
    this.receivedEnd = false;

    this.closeTimeout = this.config.closeTimeout;
    this.assembleFragments = this.config.assembleFragments;
    this.maxReceivedMessageSize = this.config.maxReceivedMessageSize;

    this.outputBufferFull = false;
    this.inputPaused = false;
    this.receivedDataHandler = this.processReceivedData.bind(this);
    this._closeTimerHandler = this.handleCloseTimer.bind(this);

    // Disable nagle algorithm?
    this.socket.setNoDelay(this.config.disableNagleAlgorithm);

    // Make sure there is no socket inactivity timeout
    this.socket.setTimeout(0);

    if (this.config.keepalive && !this.config.useNativeKeepalive) {
        if (typeof(this.config.keepaliveInterval) !== 'number') {
            throw new Error('keepaliveInterval must be specified and numeric ' +
                            'if keepalive is true.');
        }
        this._keepaliveTimerHandler = this.handleKeepaliveTimer.bind(this);
        this.setKeepaliveTimer();

        if (this.config.dropConnectionOnKeepaliveTimeout) {
            if (typeof(this.config.keepaliveGracePeriod) !== 'number') {
                throw new Error('keepaliveGracePeriod  must be specified and ' +
                                'numeric if dropConnectionOnKeepaliveTimeout ' +
                                'is true.');
            }
            this._gracePeriodTimerHandler = this.handleGracePeriodTimer.bind(this);
        }
    }
    else if (this.config.keepalive && this.config.useNativeKeepalive) {
        if (!('setKeepAlive' in this.socket)) {
            throw new Error('Unable to use native keepalive: unsupported by ' +
                            'this version of Node.');
        }
        this.socket.setKeepAlive(true, this.config.keepaliveInterval);
    }
    
    // The HTTP Client seems to subscribe to socket error events
    // and re-dispatch them in such a way that doesn't make sense
    // for users of our client, so we want to make sure nobody
    // else is listening for error events on the socket besides us.
    this.socket.removeAllListeners('error');
}

WebSocketConnection.CLOSE_REASON_NORMAL = 1000;
WebSocketConnection.CLOSE_REASON_GOING_AWAY = 1001;
WebSocketConnection.CLOSE_REASON_PROTOCOL_ERROR = 1002;
WebSocketConnection.CLOSE_REASON_UNPROCESSABLE_INPUT = 1003;
WebSocketConnection.CLOSE_REASON_RESERVED = 1004; // Reserved value.  Undefined meaning.
WebSocketConnection.CLOSE_REASON_NOT_PROVIDED = 1005; // Not to be used on the wire
WebSocketConnection.CLOSE_REASON_ABNORMAL = 1006; // Not to be used on the wire
WebSocketConnection.CLOSE_REASON_INVALID_DATA = 1007;
WebSocketConnection.CLOSE_REASON_POLICY_VIOLATION = 1008;
WebSocketConnection.CLOSE_REASON_MESSAGE_TOO_BIG = 1009;
WebSocketConnection.CLOSE_REASON_EXTENSION_REQUIRED = 1010;
WebSocketConnection.CLOSE_REASON_INTERNAL_SERVER_ERROR = 1011;
WebSocketConnection.CLOSE_REASON_TLS_HANDSHAKE_FAILED = 1015; // Not to be used on the wire

WebSocketConnection.CLOSE_DESCRIPTIONS = {
    1000: 'Normal connection closure',
    1001: 'Remote peer is going away',
    1002: 'Protocol error',
    1003: 'Unprocessable input',
    1004: 'Reserved',
    1005: 'Reason not provided',
    1006: 'Abnormal closure, no further detail available',
    1007: 'Invalid data received',
    1008: 'Policy violation',
    1009: 'Message too big',
    1010: 'Extension requested by client is required',
    1011: 'Internal Server Error',
    1015: 'TLS Handshake Failed'
};

function validateCloseReason(code) {
    if (code < 1000) {
        // Status codes in the range 0-999 are not used
        return false;
    }
    if (code >= 1000 && code <= 2999) {
        // Codes from 1000 - 2999 are reserved for use by the protocol.  Only
        // a few codes are defined, all others are currently illegal.
        return [1000, 1001, 1002, 1003, 1007, 1008, 1009, 1010, 1011, 1012, 1013, 1014].indexOf(code) !== -1;
    }
    if (code >= 3000 && code <= 3999) {
        // Reserved for use by libraries, frameworks, and applications.
        // Should be registered with IANA.  Interpretation of these codes is
        // undefined by the WebSocket protocol.
        return true;
    }
    if (code >= 4000 && code <= 4999) {
        // Reserved for private use.  Interpretation of these codes is
        // undefined by the WebSocket protocol.
        return true;
    }
    if (code >= 5000) {
        return false;
    }
}

util.inherits(WebSocketConnection, EventEmitter);

WebSocketConnection.prototype._addSocketEventListeners = function() {
    this.socket.on('error', this.handleSocketError.bind(this));
    this.socket.on('end', this.handleSocketEnd.bind(this));
    this.socket.on('close', this.handleSocketClose.bind(this));
    this.socket.on('drain', this.handleSocketDrain.bind(this));
    this.socket.on('pause', this.handleSocketPause.bind(this));
    this.socket.on('resume', this.handleSocketResume.bind(this));
    this.socket.on('data', this.handleSocketData.bind(this));
};

// set or reset the keepalive timer when data is received.
WebSocketConnection.prototype.setKeepaliveTimer = function() {
    this._debug('setKeepaliveTimer');
    if (!this.config.keepalive  || this.config.useNativeKeepalive) { return; }
    this.clearKeepaliveTimer();
    this.clearGracePeriodTimer();
    this._keepaliveTimeoutID = setTimeout(this._keepaliveTimerHandler, this.config.keepaliveInterval);
};

WebSocketConnection.prototype.clearKeepaliveTimer = function() {
    if (this._keepaliveTimeoutID) {
        clearTimeout(this._keepaliveTimeoutID);
    }
};

// No data has been received within config.keepaliveTimeout ms.
WebSocketConnection.prototype.handleKeepaliveTimer = function() {
    this._debug('handleKeepaliveTimer');
    this._keepaliveTimeoutID = null;
    this.ping();

    // If we are configured to drop connections if the client doesn't respond
    // then set the grace period timer.
    if (this.config.dropConnectionOnKeepaliveTimeout) {
        this.setGracePeriodTimer();
    }
    else {
        // Otherwise reset the keepalive timer to send the next ping.
        this.setKeepaliveTimer();
    }
};

WebSocketConnection.prototype.setGracePeriodTimer = function() {
    this._debug('setGracePeriodTimer');
    this.clearGracePeriodTimer();
    this._gracePeriodTimeoutID = setTimeout(this._gracePeriodTimerHandler, this.config.keepaliveGracePeriod);
};

WebSocketConnection.prototype.clearGracePeriodTimer = function() {
    if (this._gracePeriodTimeoutID) {
        clearTimeout(this._gracePeriodTimeoutID);
    }
};

WebSocketConnection.prototype.handleGracePeriodTimer = function() {
    this._debug('handleGracePeriodTimer');
    // If this is called, the client has not responded and is assumed dead.
    this._gracePeriodTimeoutID = null;
    this.drop(WebSocketConnection.CLOSE_REASON_ABNORMAL, 'Peer not responding.', true);
};

WebSocketConnection.prototype.handleSocketData = function(data) {
    this._debug('handleSocketData');
    // Reset the keepalive timer when receiving data of any kind.
    this.setKeepaliveTimer();

    // Add received data to our bufferList, which efficiently holds received
    // data chunks in a linked list of Buffer objects.
    this.bufferList.write(data);

    this.processReceivedData();
};

WebSocketConnection.prototype.processReceivedData = function() {
    this._debug('processReceivedData');
    // If we're not connected, we should ignore any data remaining on the buffer.
    if (!this.connected) { return; }

    // Receiving/parsing is expected to be halted when paused.
    if (this.inputPaused) { return; }

    var frame = this.currentFrame;

    // WebSocketFrame.prototype.addData returns true if all data necessary to
    // parse the frame was available.  It returns false if we are waiting for
    // more data to come in on the wire.
    if (!frame.addData(this.bufferList)) { this._debug('-- insufficient data for frame'); return; }

    var self = this;

    // Handle possible parsing errors
    if (frame.protocolError) {
        // Something bad happened.. get rid of this client.
        this._debug('-- protocol error');
        process.nextTick(function() {
            self.drop(WebSocketConnection.CLOSE_REASON_PROTOCOL_ERROR, frame.dropReason);
        });
        return;
    }
    else if (frame.frameTooLarge) {
        this._debug('-- frame too large');
        process.nextTick(function() {
            self.drop(WebSocketConnection.CLOSE_REASON_MESSAGE_TOO_BIG, frame.dropReason);
        });
        return;
    }

    // For now since we don't support extensions, all RSV bits are illegal
    if (frame.rsv1 || frame.rsv2 || frame.rsv3) {
        this._debug('-- illegal rsv flag');
        process.nextTick(function() {
            self.drop(WebSocketConnection.CLOSE_REASON_PROTOCOL_ERROR,
              'Unsupported usage of rsv bits without negotiated extension.');
        });
        return;
    }

    if (!this.assembleFragments) {
        this._debug('-- emitting frame');
        process.nextTick(function() { self.emit('frame', frame); });
    }

    process.nextTick(function() { self.processFrame(frame); });
    
    this.currentFrame = new WebSocketFrame(this.maskBytes, this.frameHeader, this.config);

    // If there's data remaining, schedule additional processing, but yield
    // for now so that other connections have a chance to have their data
    // processed.  We use setImmediate here instead of process.nextTick to
    // explicitly indicate that we wish for other I/O to be handled first.
    if (this.bufferList.length > 0) {
        setImmediateImpl(this.receivedDataHandler);
    }
};

WebSocketConnection.prototype.handleSocketError = function(error) {
    this._debug('handleSocketError: %j', error);
    if (this.state === STATE_CLOSED) {
		// See https://github.com/theturtle32/WebSocket-Node/issues/288
        this._debug('  --- Socket \'error\' after \'close\'');
        return;
    }
    this.closeReasonCode = WebSocketConnection.CLOSE_REASON_ABNORMAL;
    this.closeDescription = 'Socket Error: ' + error.syscall + ' ' + error.code;
    this.connected = false;
    this.state = STATE_CLOSED;
    this.fragmentationSize = 0;
    if (utils.eventEmitterListenerCount(this, 'error') > 0) {
        this.emit('error', error);
    }
    this.socket.destroy();
    this._debug.printOutput();
};

WebSocketConnection.prototype.handleSocketEnd = function() {
    this._debug('handleSocketEnd: received socket end.  state = %s', this.state);
    this.receivedEnd = true;
    if (this.state === STATE_CLOSED) {
        // When using the TLS module, sometimes the socket will emit 'end'
        // after it emits 'close'.  I don't think that's correct behavior,
        // but we should deal with it gracefully by ignoring it.
        this._debug('  --- Socket \'end\' after \'close\'');
        return;
    }
    if (this.state !== STATE_PEER_REQUESTED_CLOSE &&
        this.state !== STATE_ENDING) {
      this._debug('  --- UNEXPECTED socket end.');
      this.socket.end();
    }
};

WebSocketConnection.prototype.handleSocketClose = function(hadError) {
    this._debug('handleSocketClose: received socket close');
    this.socketHadError = hadError;
    this.connected = false;
    this.state = STATE_CLOSED;
    // If closeReasonCode is still set to -1 at this point then we must
    // not have received a close frame!!
    if (this.closeReasonCode === -1) {
        this.closeReasonCode = WebSocketConnection.CLOSE_REASON_ABNORMAL;
        this.closeDescription = 'Connection dropped by remote peer.';
    }
    this.clearCloseTimer();
    this.clearKeepaliveTimer();
    this.clearGracePeriodTimer();
    if (!this.closeEventEmitted) {
        this.closeEventEmitted = true;
        this._debug('-- Emitting WebSocketConnection close event');
        this.emit('close', this.closeReasonCode, this.closeDescription);
    }
};

WebSocketConnection.prototype.handleSocketDrain = function() {
    this._debug('handleSocketDrain: socket drain event');
    this.outputBufferFull = false;
    this.emit('drain');
};

WebSocketConnection.prototype.handleSocketPause = function() {
    this._debug('handleSocketPause: socket pause event');
    this.inputPaused = true;
    this.emit('pause');
};

WebSocketConnection.prototype.handleSocketResume = function() {
    this._debug('handleSocketResume: socket resume event');
    this.inputPaused = false;
    this.emit('resume');
    this.processReceivedData();
};

WebSocketConnection.prototype.pause = function() {
    this._debug('pause: pause requested');
    this.socket.pause();
};

WebSocketConnection.prototype.resume = function() {
    this._debug('resume: resume requested');
    this.socket.resume();
};

WebSocketConnection.prototype.close = function(reasonCode, description) {
    if (this.connected) {
        this._debug('close: Initating clean WebSocket close sequence.');
        if ('number' !== typeof reasonCode) {
            reasonCode = WebSocketConnection.CLOSE_REASON_NORMAL;
        }
        if (!validateCloseReason(reasonCode)) {
            throw new Error('Close code ' + reasonCode + ' is not valid.');
        }
        if ('string' !== typeof description) {
            description = WebSocketConnection.CLOSE_DESCRIPTIONS[reasonCode];
        }
        this.closeReasonCode = reasonCode;
        this.closeDescription = description;
        this.setCloseTimer();
        this.sendCloseFrame(this.closeReasonCode, this.closeDescription);
        this.state = STATE_ENDING;
        this.connected = false;
    }
};

WebSocketConnection.prototype.drop = function(reasonCode, description, skipCloseFrame) {
    this._debug('drop');
    if (typeof(reasonCode) !== 'number') {
        reasonCode = WebSocketConnection.CLOSE_REASON_PROTOCOL_ERROR;
    }

    if (typeof(description) !== 'string') {
        // If no description is provided, try to look one up based on the
        // specified reasonCode.
        description = WebSocketConnection.CLOSE_DESCRIPTIONS[reasonCode];
    }

    this._debug('Forcefully dropping connection. skipCloseFrame: %s, code: %d, description: %s',
        skipCloseFrame, reasonCode, description
    );

    this.closeReasonCode = reasonCode;
    this.closeDescription = description;
    this.frameQueue = [];
    this.fragmentationSize = 0;
    if (!skipCloseFrame) {
        this.sendCloseFrame(reasonCode, description);
    }
    this.connected = false;
    this.state = STATE_CLOSED;
    this.clearCloseTimer();
    this.clearKeepaliveTimer();
    this.clearGracePeriodTimer();

    if (!this.closeEventEmitted) {
        this.closeEventEmitted = true;
        this._debug('Emitting WebSocketConnection close event');
        this.emit('close', this.closeReasonCode, this.closeDescription);
    }
    
    this._debug('Drop: destroying socket');
    this.socket.destroy();
};

WebSocketConnection.prototype.setCloseTimer = function() {
    this._debug('setCloseTimer');
    this.clearCloseTimer();
    this._debug('Setting close timer');
    this.waitingForCloseResponse = true;
    this.closeTimer = setTimeout(this._closeTimerHandler, this.closeTimeout);
};

WebSocketConnection.prototype.clearCloseTimer = function() {
    this._debug('clearCloseTimer');
    if (this.closeTimer) {
        this._debug('Clearing close timer');
        clearTimeout(this.closeTimer);
        this.waitingForCloseResponse = false;
        this.closeTimer = null;
    }
};

WebSocketConnection.prototype.handleCloseTimer = function() {
    this._debug('handleCloseTimer');
    this.closeTimer = null;
    if (this.waitingForCloseResponse) {
        this._debug('Close response not received from client.  Forcing socket end.');
        this.waitingForCloseResponse = false;
        this.state = STATE_CLOSED;
        this.socket.end();
    }
};

WebSocketConnection.prototype.processFrame = function(frame) {
    this._debug('processFrame');
    this._debug(' -- frame: %s', frame);
    
    // Any non-control opcode besides 0x00 (continuation) received in the
    // middle of a fragmented message is illegal.
    if (this.frameQueue.length !== 0 && (frame.opcode > 0x00 && frame.opcode < 0x08)) {
        this.drop(WebSocketConnection.CLOSE_REASON_PROTOCOL_ERROR,
          'Illegal frame opcode 0x' + frame.opcode.toString(16) + ' ' +
          'received in middle of fragmented message.');
        return;
    }

    switch(frame.opcode) {
        case 0x02: // WebSocketFrame.BINARY_FRAME
            this._debug('-- Binary Frame');
            if (this.assembleFragments) {
                if (frame.fin) {
                    // Complete single-frame message received
                    this._debug('---- Emitting \'message\' event');
                    this.emit('message', {
                        type: 'binary',
                        binaryData: frame.binaryPayload
                    });
                }
                else {
                    // beginning of a fragmented message
                    this.frameQueue.push(frame);
                    this.fragmentationSize = frame.length;
                }
            }
            break;
        case 0x01: // WebSocketFrame.TEXT_FRAME
            this._debug('-- Text Frame');
            if (this.assembleFragments) {
                if (frame.fin) {
                    if (!Validation.isValidUTF8(frame.binaryPayload)) {
                        this.drop(WebSocketConnection.CLOSE_REASON_INVALID_DATA,
                          'Invalid UTF-8 Data Received');
                        return;
                    }
                    // Complete single-frame message received
                    this._debug('---- Emitting \'message\' event');
                    this.emit('message', {
                        type: 'utf8',
                        utf8Data: frame.binaryPayload.toString('utf8')
                    });
                }
                else {
                    // beginning of a fragmented message
                    this.frameQueue.push(frame);
                    this.fragmentationSize = frame.length;
                }
            }
            break;
        case 0x00: // WebSocketFrame.CONTINUATION
            this._debug('-- Continuation Frame');
            if (this.assembleFragments) {
                if (this.frameQueue.length === 0) {
                    this.drop(WebSocketConnection.CLOSE_REASON_PROTOCOL_ERROR,
                      'Unexpected Continuation Frame');
                    return;
                }

                this.fragmentationSize += frame.length;

                if (this.fragmentationSize > this.maxReceivedMessageSize) {
                    this.drop(WebSocketConnection.CLOSE_REASON_MESSAGE_TOO_BIG,
                      'Maximum message size exceeded.');
                    return;
                }

                this.frameQueue.push(frame);

                if (frame.fin) {
                    // end of fragmented message, so we process the whole
                    // message now.  We also have to decode the utf-8 data
                    // for text frames after combining all the fragments.
                    var bytesCopied = 0;
                    var binaryPayload = bufferAllocUnsafe(this.fragmentationSize);
                    var opcode = this.frameQueue[0].opcode;
                    this.frameQueue.forEach(function (currentFrame) {
                        currentFrame.binaryPayload.copy(binaryPayload, bytesCopied);
                        bytesCopied += currentFrame.binaryPayload.length;
                    });
                    this.frameQueue = [];
                    this.fragmentationSize = 0;

                    switch (opcode) {
                        case 0x02: // WebSocketOpcode.BINARY_FRAME
                            this.emit('message', {
                                type: 'binary',
                                binaryData: binaryPayload
                            });
                            break;
                        case 0x01: // WebSocketOpcode.TEXT_FRAME
                            if (!Validation.isValidUTF8(binaryPayload)) {
                                this.drop(WebSocketConnection.CLOSE_REASON_INVALID_DATA,
                                  'Invalid UTF-8 Data Received');
                                return;
                            }
                            this.emit('message', {
                                type: 'utf8',
                                utf8Data: binaryPayload.toString('utf8')
                            });
                            break;
                        default:
                            this.drop(WebSocketConnection.CLOSE_REASON_PROTOCOL_ERROR,
                              'Unexpected first opcode in fragmentation sequence: 0x' + opcode.toString(16));
                            return;
                    }
                }
            }
            break;
        case 0x09: // WebSocketFrame.PING
            this._debug('-- Ping Frame');

            if (this._pingListenerCount > 0) {
                // logic to emit the ping frame: this is only done when a listener is known to exist
                // Expose a function allowing the user to override the default ping() behavior
                var cancelled = false;
                var cancel = function() { 
                  cancelled = true; 
                };
                this.emit('ping', cancel, frame.binaryPayload);

                // Only send a pong if the client did not indicate that he would like to cancel
                if (!cancelled) {
                    this.pong(frame.binaryPayload);
                }
            }
            else {
                this.pong(frame.binaryPayload);
            }

            break;
        case 0x0A: // WebSocketFrame.PONG
            this._debug('-- Pong Frame');
            this.emit('pong', frame.binaryPayload);
            break;
        case 0x08: // WebSocketFrame.CONNECTION_CLOSE
            this._debug('-- Close Frame');
            if (this.waitingForCloseResponse) {
                // Got response to our request to close the connection.
                // Close is complete, so we just hang up.
                this._debug('---- Got close response from peer.  Completing closing handshake.');
                this.clearCloseTimer();
                this.waitingForCloseResponse = false;
                this.state = STATE_CLOSED;
                this.socket.end();
                return;
            }
            
            this._debug('---- Closing handshake initiated by peer.');
            // Got request from other party to close connection.
            // Send back acknowledgement and then hang up.
            this.state = STATE_PEER_REQUESTED_CLOSE;
            var respondCloseReasonCode;

            // Make sure the close reason provided is legal according to
            // the protocol spec.  Providing no close status is legal.
            // WebSocketFrame sets closeStatus to -1 by default, so if it
            // is still -1, then no status was provided.
            if (frame.invalidCloseFrameLength) {
                this.closeReasonCode = 1005; // 1005 = No reason provided.
                respondCloseReasonCode = WebSocketConnection.CLOSE_REASON_PROTOCOL_ERROR;
            }
            else if (frame.closeStatus === -1 || validateCloseReason(frame.closeStatus)) {
                this.closeReasonCode = frame.closeStatus;
                respondCloseReasonCode = WebSocketConnection.CLOSE_REASON_NORMAL;
            }
            else {
                this.closeReasonCode = frame.closeStatus;
                respondCloseReasonCode = WebSocketConnection.CLOSE_REASON_PROTOCOL_ERROR;
            }
            
            // If there is a textual description in the close frame, extract it.
            if (frame.binaryPayload.length > 1) {
                if (!Validation.isValidUTF8(frame.binaryPayload)) {
                    this.drop(WebSocketConnection.CLOSE_REASON_INVALID_DATA,
                      'Invalid UTF-8 Data Received');
                    return;
                }
                this.closeDescription = frame.binaryPayload.toString('utf8');
            }
            else {
                this.closeDescription = WebSocketConnection.CLOSE_DESCRIPTIONS[this.closeReasonCode];
            }
            this._debug(
                '------ Remote peer %s - code: %d - %s - close frame payload length: %d',
                this.remoteAddress, this.closeReasonCode,
                this.closeDescription, frame.length
            );
            this._debug('------ responding to remote peer\'s close request.');
            this.sendCloseFrame(respondCloseReasonCode, null);
            this.connected = false;
            break;
        default:
            this._debug('-- Unrecognized Opcode %d', frame.opcode);
            this.drop(WebSocketConnection.CLOSE_REASON_PROTOCOL_ERROR,
              'Unrecognized Opcode: 0x' + frame.opcode.toString(16));
            break;
    }
};

WebSocketConnection.prototype.send = function(data, cb) {
    this._debug('send');
    if (Buffer.isBuffer(data)) {
        this.sendBytes(data, cb);
    }
    else if (typeof(data['toString']) === 'function') {
        this.sendUTF(data, cb);
    }
    else {
        throw new Error('Data provided must either be a Node Buffer or implement toString()');
    }
};

WebSocketConnection.prototype.sendUTF = function(data, cb) {
    data = bufferFromString(data.toString(), 'utf8');
    this._debug('sendUTF: %d bytes', data.length);
    var frame = new WebSocketFrame(this.maskBytes, this.frameHeader, this.config);
    frame.opcode = 0x01; // WebSocketOpcode.TEXT_FRAME
    frame.binaryPayload = data;
    this.fragmentAndSend(frame, cb);
};

WebSocketConnection.prototype.sendBytes = function(data, cb) {
    this._debug('sendBytes');
    if (!Buffer.isBuffer(data)) {
        throw new Error('You must pass a Node Buffer object to WebSocketConnection.prototype.sendBytes()');
    }
    var frame = new WebSocketFrame(this.maskBytes, this.frameHeader, this.config);
    frame.opcode = 0x02; // WebSocketOpcode.BINARY_FRAME
    frame.binaryPayload = data;
    this.fragmentAndSend(frame, cb);
};

WebSocketConnection.prototype.ping = function(data) {
    this._debug('ping');
    var frame = new WebSocketFrame(this.maskBytes, this.frameHeader, this.config);
    frame.opcode = 0x09; // WebSocketOpcode.PING
    frame.fin = true;
    if (data) {
        if (!Buffer.isBuffer(data)) {
            data = bufferFromString(data.toString(), 'utf8');
        }
        if (data.length > 125) {
            this._debug('WebSocket: Data for ping is longer than 125 bytes.  Truncating.');
            data = data.slice(0,124);
        }
        frame.binaryPayload = data;
    }
    this.sendFrame(frame);
};

// Pong frames have to echo back the contents of the data portion of the
// ping frame exactly, byte for byte.
WebSocketConnection.prototype.pong = function(binaryPayload) {
    this._debug('pong');
    var frame = new WebSocketFrame(this.maskBytes, this.frameHeader, this.config);
    frame.opcode = 0x0A; // WebSocketOpcode.PONG
    if (Buffer.isBuffer(binaryPayload) && binaryPayload.length > 125) {
        this._debug('WebSocket: Data for pong is longer than 125 bytes.  Truncating.');
        binaryPayload = binaryPayload.slice(0,124);
    }
    frame.binaryPayload = binaryPayload;
    frame.fin = true;
    this.sendFrame(frame);
};

WebSocketConnection.prototype.fragmentAndSend = function(frame, cb) {
    this._debug('fragmentAndSend');
    if (frame.opcode > 0x07) {
        throw new Error('You cannot fragment control frames.');
    }

    var threshold = this.config.fragmentationThreshold;
    var length = frame.binaryPayload.length;

    // Send immediately if fragmentation is disabled or the message is not
    // larger than the fragmentation threshold.
    if (!this.config.fragmentOutgoingMessages || (frame.binaryPayload && length <= threshold)) {
        frame.fin = true;
        this.sendFrame(frame, cb);
        return;
    }
    
    var numFragments = Math.ceil(length / threshold);
    var sentFragments = 0;
    var sentCallback = function fragmentSentCallback(err) {
        if (err) {
            if (typeof cb === 'function') {
                // pass only the first error
                cb(err);
                cb = null;
            }
            return;
        }
        ++sentFragments;
        if ((sentFragments === numFragments) && (typeof cb === 'function')) {
            cb();
        }
    };
    for (var i=1; i <= numFragments; i++) {
        var currentFrame = new WebSocketFrame(this.maskBytes, this.frameHeader, this.config);
        
        // continuation opcode except for first frame.
        currentFrame.opcode = (i === 1) ? frame.opcode : 0x00;
        
        // fin set on last frame only
        currentFrame.fin = (i === numFragments);
        
        // length is likely to be shorter on the last fragment
        var currentLength = (i === numFragments) ? length - (threshold * (i-1)) : threshold;
        var sliceStart = threshold * (i-1);
        
        // Slice the right portion of the original payload
        currentFrame.binaryPayload = frame.binaryPayload.slice(sliceStart, sliceStart + currentLength);
        
        this.sendFrame(currentFrame, sentCallback);
    }
};

WebSocketConnection.prototype.sendCloseFrame = function(reasonCode, description, cb) {
    if (typeof(reasonCode) !== 'number') {
        reasonCode = WebSocketConnection.CLOSE_REASON_NORMAL;
    }
    
    this._debug('sendCloseFrame state: %s, reasonCode: %d, description: %s', this.state, reasonCode, description);
    
    if (this.state !== STATE_OPEN && this.state !== STATE_PEER_REQUESTED_CLOSE) { return; }
    
    var frame = new WebSocketFrame(this.maskBytes, this.frameHeader, this.config);
    frame.fin = true;
    frame.opcode = 0x08; // WebSocketOpcode.CONNECTION_CLOSE
    frame.closeStatus = reasonCode;
    if (typeof(description) === 'string') {
        frame.binaryPayload = bufferFromString(description, 'utf8');
    }
    
    this.sendFrame(frame, cb);
    this.socket.end();
};

WebSocketConnection.prototype.sendFrame = function(frame, cb) {
    this._debug('sendFrame');
    frame.mask = this.maskOutgoingPackets;
    var flushed = this.socket.write(frame.toBuffer(), cb);
    this.outputBufferFull = !flushed;
    return flushed;
};

module.exports = WebSocketConnection;



function instrumentSocketForDebugging(connection, socket) {
    /* jshint loopfunc: true */
    if (!connection._debug.enabled) { return; }
    
    var originalSocketEmit = socket.emit;
    socket.emit = function(event) {
        connection._debug('||| Socket Event  \'%s\'', event);
        originalSocketEmit.apply(this, arguments);
    };
    
    for (var key in socket) {
        if ('function' !== typeof(socket[key])) { continue; }
        if (['emit'].indexOf(key) !== -1) { continue; }
        (function(key) {
            var original = socket[key];
            if (key === 'on') {
                socket[key] = function proxyMethod__EventEmitter__On() {
                    connection._debug('||| Socket method called:  %s (%s)', key, arguments[0]);
                    return original.apply(this, arguments);
                };
                return;
            }
            socket[key] = function proxyMethod() {
                connection._debug('||| Socket method called:  %s', key);
                return original.apply(this, arguments);
            };
        })(key);
    }
}