socket.io连接问题

Question

I keep getting this GET /socket.io/?EIO=3&transport=polling&t=MfRfeJD 404 4.438 ms - 149 error and I don't know where it's coming from.

I'm trying to integrate a live chat into my application using react, socket.io and express and I keep getting this not found error with the sockets. I'm not sure if the problem is on the client or server side. It appears to be trying to continuously poll the server, but is getting 404's back. That sounds like socket.io isn't running, but it all looks okay to me. It may also have something to do with paths, but I don't really know. I've tried adding different route to the io like " http://localhost:5000/ " but still it still can't find the socket.

I get the page to show up and when I click send the message shows up but I can't get the sockets to connect.

In app.js

    const express = require('express');

  const http = require('http')
    const bodyParser = require('body-parser')
    const socketIo = require('socket.io')

    var app = express();
    const server = http.createServer(app)
    const io = socketIo(server)

    var PORT = process.env.PORT || 5000;

    app.post('/', (req, res) => {
      const { Body, From} = req.body
      const message = {
        body: Body,
        from: From.slice(8),

      }
      io.emit('message', message)
      res.send(`
               <Response>
                <Message>Thanks for texting!</Message>
               </Response>
               `)
    })

    io.on('connection', socket => {
      socket.on('message', body => {
        socket.broadcast.emit('message', {
          body,
          from: socket.id.slice(8)
        })
      })
    })

    server.listen(PORT);

In Chat.js

    import React from "react";
    import io from "socket.io-client";



    class Chat extends React.Component {
        constructor (props) {
          super(props)
          this.state = { messages: [] }
        }

        componentDidMount () {
          this.socket = io('http://localhost:5000/')
          this.socket.on('message', message => {
            this.setState({ messages: [message, ...this.state.messages] })
          })
        }

        handleSubmit = event => {
          const body = event.target.value
          if (event.keyCode === 13 && body) {
            const message = {
              body,
              from: 'Me'
            }
            this.setState({ messages: [message, ...this.state.messages] })
            this.socket.emit('message', body)
            event.target.value = ''
          }
        }

        render () {
          const messages = this.state.messages.map((message, index) => {
            return <li key={index}><b>{message.from}:</b>{message.body} </li>
          })
          return (
            <div>
               <h1>Admin Chat</h1>
              <input type='text' placeholder='Enter a message...' onKeyUp={this.handleSubmit} />
              {messages}
            </div>
          )
        }
      }



export default Chat;

Answer 1

404 is clearly saying no such page

149 will be the line number of the failure, your importing other code so it can be on any of the other code that the line 149 exists

i do see a maybe in app.js and the path 
 "app.post('/', (req, res) => {"        Refers to an absolute path
     try changing "http://localhost:5000/" 
       to "http://localhost:5000" or "http://localhost/:5000"

it looks like the "/" on the end puts the 5000 in the path not the port

--- EDIT --- on closer look at GET /socket.io/?EIO=3&transport=polling&t=MfRfeJD

if chat.js is running on the client and connecting to http://localhost:5000 than;

http://localhost/socket.io/?EIO=3&transport=polling&t=MfRfeJD would be the attempted connection

it looks like client is trying to connect back to itself.

how do you have the client / server setup?

if they are separate machines this would be looking for a non existing url.

either way is happening in the socket.io library.