UC故事2011/10/11

最新推荐文章于 2019-10-31 19:11:13 发布

原创最新推荐文章于 2019-10-31 19:11:13 发布 · 374 阅读

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文章标签：

#websocket #filter #protocols #methods #tcp #server

本文深入探讨了HTTP1.1与HTTP1.0的区别，详细解释了如何使用一个TCP连接处理多个到同一服务器的请求，并介绍了HTTP方法的安全性和不安全性。同时，文章还对比了CONNECT方法与代理协议的作用，阐述了WebSocket协议的特性与应用，包括两向通信通过单一TCP连接实现，以及其设计哲学。此外，文章还涵盖了WebSocket的握手过程、帧结构和与TCP、HTTP的关系，最后讨论了80与443端口的差异。

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1. HTTP review

* HTTP1.1 vs HTTP 1.0

使用一个TCP Connection处理多个到同一Server的请求

* HTTP Methods

Safe methods: HEAD, GET, OPTIONS, TRACE

Unsafe methods: POST, PUT, DELETE

* CONNECT （代理协议）

Converts the request connection to a transparent TCP/IP tunnel, usually to facilitate SSL-encrypted communication (HTTPS) through an unencrypted HTTP proxy.

2. HTML5 WebSocket

* 升级（与CONNECT方法无关）

一个WebSocket连接是在客户端与服务器之间HTTP协议的初始握手阶段将其升级到Web Socket协议来建立的，其底层仍是TCP/IP连接。

 GET /text HTTP/1.1\r\n  
Upgrade: WebSocket\r\n  
Connection: Upgrade\r\n  
Host: www.websocket.org\r\n  
...\r\n  
HTTP/1.1 101 WebSocket Protocol Handshake\r\n  
Upgrade: WebSocket\r\n  
Connection: Upgrade\r\n  
...\r\n

3. 阅读WebSocket的memo

http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-10

* 2-way communications via 1 single TCP Connection

* design philosophy

minmal framing

Note: compared with TCP

# origin-based security model

# multiple services on one port / multiple host names on one IP

# framing mechanism

# additinal closing handshake in-band

* relationship to TCP, HTTP

on top of TCP

HTTP: the only relationship is that its handshake is interpreted by HTTP servers as an Upgrade request.

* opening handshake

client side:

        GET /chat HTTP/1.1
        Host: server.example.com
        Upgrade: websocket
        Connection: Upgrade
        Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
        Sec-WebSocket-Origin: http://example.com
        Sec-WebSocket-Protocol: chat, superchat
        Sec-WebSocket-Version: 8

server side:

        HTTP/1.1 101 Switching Protocols
        Upgrade: websocket
        Connection: Upgrade
        Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
        Sec-WebSocket-Protocol: chat

* Framing

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-------+-+-------------+-------------------------------+
     |F|R|R|R| opcode|M| Payload len |    Extended payload length    |
     |I|S|S|S| (4) |A|     (7)     |             (16/63)           |
     |N|V|V|V|       |S|             |   (if payload len==126/127)   |
     | |1|2|3|       |K|             |                               |
     +-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
     |     Extended payload length continued, if payload len == 127 |
     + - - - - - - - - - - - - - - - +-------------------------------+
     |                               |Masking-key, if MASK set to 1 |
     +-------------------------------+-------------------------------+
     | Masking-key (continued)       |          Payload Data         |
     +-------------------------------- - - - - - - - - - - - - - - - +
     :                     Payload Data continued ...                :
     + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
     |                     Payload Data continued ...                |
     +---------------------------------------------------------------+

Q: 关于80与443的奇怪事情

At the time of writing of this
   specification, it should be noted that connections on port 80 and 443
   have significantly different success rates, with connections on port
   443 being significantly more likely to succeed, though this may
   change with time.

4. wireshark

* filters

有两种filter，一种是capture filter，另一种是display filter，分别有不同的语法。

* display filter

Some filter fields match against multiple protocol fields. For example, "ip.addr" matches against both the IP source and destination addresses in the IP header. The same is true for "tcp.port", "udp.port", "eth.addr", and others.

e.g:

ip.addr == 10.43.54.65 equals to ip.src == 10.43.54.65 or ip.dst == 10.43.54.65.

!(ip.addr == 10.43.54.65) vs. ip.addr != 10.43.54.65