2)当不支持XHR2并且发送二进制数据,但是使用base64编码字符串的时候,其编码格式是:<length of base64 representation of the data + 1 (for packet type)>:b<packet1 type><packet1 data in b64>[...];
3)当支持XHR2的时候,所有的数据都被编码成二进制,格式是:<0 for string data, 1 for binary data><Any number of numbers between 0 and 9><The number 255><packet1 (first type, then data)>[...];