polling方式一直连不上，尝试很多次后能成功！

[KevinGitHub1]

服务端报错：
ERROR 6968 --- [tLoopGroup-3-56] c.c.socketio.transport.PollingTransport : 848d39bf-73ef-4415-8047-3d64f14bce03 is not registered. Closing connection
客户端报错： http://ip:9099/socket.io/?loginUser=5555&EIO=3&transport=polling&t=MlvmOQ5&sid=848d39bf-73ef-4415-8047-3d64f14bce03 net::ERR_CONNECTION_RESET
i.create @ socket.io.js:7
i @ socket.io.js:7
o.request @ socket.io.js:7
o.doPoll @ socket.io.js:7
r.poll @ socket.io.js:7
r.onData @ socket.io.js:7
(anonymous) @ socket.io.js:7
r.emit @ socket.io.js:6
i.onData @ socket.io.js:7
i.onLoad @ socket.io.js:7
hasXDR.e.onreadystatechange @ socket.io.js:7
XMLHttpRequest.send (async)
i.create @ socket.io.js:7
i @ socket.io.js:7
o.request @ socket.io.js:7
o.doPoll @ socket.io.js:7
r.poll @ socket.io.js:7
r.doOpen @ socket.io.js:7
r.open @ socket.io.js:7
r.open @ socket.io.js:6
r @ socket.io.js:6
r @ socket.io.js:6
r.open.r.connect @ socket.io.js:6
r @ socket.io.js:6
r @ socket.io.js:6
r @ socket.io.js:6

Error: xhr poll error
at o.r.onError (socket.io.js:7)
at i. (socket.io.js:7)
at i.r.emit (socket.io.js:6)
at i.onError (socket.io.js:7)
at socket.io.js:7
transport error

[godtrack]

Polling很不友好，建议你用Websocket。
io('server-address', { transports: [ 'websocket' ] })

[xupengggggg]

Polling在ie9及以下很ok,，，在ie9以上很难连得不上，目前只能判断ie版本来决定要不要Websocket

[kevinhuangwl]

遇到类似问题，也是要多次重连。设了websocket，立马解决