var http = require('http');
var url = require('url');
// var mime = require('mime');
var crypto = require('crypto');

var port = 4400;
var server = http.createServer();
  server.listen(port,function() {
    console.log('server is running on localhost:',port);
    server
    .on('connection',function(s) {
      console.log('on connection ',s);
    })
    .on('request',onrequest)
    .on('upgrade',onupgrade);
  });

var onrequest = function(req,res) {
  console.log( Object.keys(req) ,req.url,req['upgrade']);
  if( !req.upgrade ){
    // 非upgrade请求选择：中断或提供普通网页
    res.writeHead(200, { 'content-type': 'text/plain' });
    res.write( 'WebSocket server works!' );
    
  }
  res.end();
  return;
};

var onupgrade = function (req,sock,head) {
  // console.log('方法:',Object.keys(sock));
  if(req.headers.upgrade !== 'WebSocket'){
    console.warn('非法连接');
    sock.end();
    return;
  }
  
  bind_sock_event(sock);

  try{
    handshake(req,sock,head);
  }catch(e){
    console.error(e);
    sock.end();
  }
};

// 包装将要发送的帧
var wrap = function(data) {
  var fa = 0x00, fe = 0xff, data = data.toString()
    len = 2+Buffer.byteLength(data),
    buff = new Buffer(len);

  buff[0] = fa;
  buff.write(data,1);
  buff[len-1] = fe;
  return buff;
}
// 解开接收到的帧
var unwrap = function(data) {
  return data.slice(1,data.length-1);
}

var bind_sock_event = function(sock) {
  sock
  .on('data',function(buffer) {
    var data = unwrap(buffer);
    console.log('socket receive data : ',buffer,data,'\n>>> '+data);
    // send('hello html5,'+Date.now())
    sock.emit('send',data);
  })
  .on('close',function() {
    console.log('socket close');
  })
  .on('end',function() {
    console.log('socket end');
  })
  .on('send',function(data) { //自定义事件
    sock.write(wrap(data),'binary');
  })
};

var get_part = function(key) {
  var empty  = '',
    spaces = key.replace(/\S/g,empty).length,
    part  = key.replace(/\D/g,empty);
  if(!spaces) throw {message:'Wrong key: '+key,name:'HandshakeError'}
  return get_big_endian(part / spaces);
}

var get_big_endian = function(n) { 
  return String.fromCharCode.apply(null,[3,2,1,0].map(function(i) { return n >> 8*i & 0xff }))
}

var challenge = function(key1,key2,head) {
  var sum = get_part(key1) + get_part(key2) + head.toString('binary');
  return crypto.createHash('md5').update(sum).digest('binary');
}

var handshake = function(req,sock,head) {
  var output = [],h = req.headers, br = '\r\n';

  // header
  output.push(
    'HTTP/1.1 101 WebSocket Protocol Handshake','Upgrade: WebSocket','Connection: Upgrade',
    'Sec-WebSocket-Origin: ' + h.origin,
    'Sec-WebSocket-Location: ws://' + h.host + req.url,
    'Sec-WebSocket-Protocol: my-custom-chat-protocol'+br
  );
  // body
  var c = challenge(h['sec-websocket-key1'],h['sec-websocket-key2'],head);
  output.push(c);

  sock.write(output.join(br),'binary');
}

  

 
 

 






send

part_1 = key1中所有数字 / key1中空格数量
part_2 同上
sum = big_endian(part_1)+big_endian(part_2)+key3
challenge_response = md5_digest(sum);

# 很类似于rgba颜色计算,从下面的函数可以看出计算过程
var big_endian = function(n) {
  return [3,2,1,0].map(function(i) { return n >> 8*i & 0xff });
}
big_endian(0xcc77aaff);
// -> [204, 119, 170, 255]