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SocketIO

socketio/socket.io
- real-time bidirectional event-based communication
socketio/socket.io-redis-adapter
- pub/sub
- socket.io#/# - broadcast
- socket.io#/#room21# - room
- <prefix>#<namespace>#*
- <prefix>-request#<namespace>#
- <prefix>-response#<namespace>#
https://admin.socket.io/

Protocol

WEBSOCKET wss://example.com/socket.io/?EIO=3&transport=websocket

EIO - 版本 - 3/4
- EngineIO v2 -> SocketIO v0.9
- EngineIO v3 -> SocketIO v1, v2
- EngineIO v4 -> SocketIO v3
  - reverse ping/pong
    - server -> client
    - 因为 client 的 timer 不一定靠谱
  - long-polling base64 binary data
  - record separator \x1e
    - 之前使用 length - 对于非 utf16 客户端实现不友好
transport - 传输协议 - websocket/polling
sid - session id

polling

Content-Type: application/octet-stream
Content-Type: text/plain; charset=UTF-8
<packet type>[<data>]<separator><packet type>[<data>]<separator><packet type>[<data>][...]
- separator=\x1e - Record Separator

WebSocket

<packet type>[<data>]

<- 0{"sid":"258c675c-a211-4bd4-a861-7b2ae022309e","upgrades":["websocket"],"pingInterval":25000,"pingTimeout":60000}
<- 40

-> 2
<- 3

engine.io type

N	for
0	open
1	close
2	ping
3	pong
4	message
5	upgrade
6	noop

open

{
  "sid": "lv_VI97HAXpY6yYWAAAC",
  "upgrades": ["websocket"],
  "pingInterval": 25000,
  "pingTimeout": 20000,
  "maxPayload": 1000000
}

socket.io action

N	for
0	CONNECT
1	DISCONNECT
2	EVENT
3	ACK
4	ERROR
5	BINARY_EVENT
6	BINARY_ACK

40 -> message/CONNECT

-> { type: CONNECT, namespace: "/admin", data: { "token": "123" } }
<- { type: CONNECT, namespace: "/admin", data: { sid: "iLnRaVGHY4B75TeVAAAB" } }

type, namespace, data
CONNECT -> CONNECT,CONNECT_ERROR
EVENT, BINARY_EVENT -> ACK, BINARY_ACK

<packet type>[<# of binary attachments>-][<namespace>,][<acknowledgment id>][JSON-stringified payload without binary]

+ binary attachments extracted

编码

{ "type": "CONNECT", "namespace": "/admin", "data": { "sid": "oSO0OpakMV_3jnilAAAA" } }

0/admin,{"sid":"oSO0OpakMV_3jnilAAAA"}

参考

FAQ

namespace vs room

相同点

命名空间和房间都是在服务端创建
服务器只会将消息分发给连接到了相应命名空间和房间的客户端

不同点

一个命名空间一个连接,一个命名空间下的房间共享一个连接
客户端可任意离开房间,但要离开命名空间只能断开连接
客户端只能连接到服务器上已经存在的命名空间
只能在服务器端进入房间,但实现一个从客户端控制服务端加入房间的命令很简单.
命名空间可进行授权验证
房间虽然不支持授权验证,但自定义一个授权验证还是很容易的.
房间是命名空间的一部分,默认为 'global' 命名空间

因此使用命名空间最好使用服务器上已经定义好的,而房间主要用于动态创建的.

Protocol
namespace vs room