How to stream data over socket.io to client

问题

I have socket.io sending a basic object from server to client. This bit works fine.

Now want to send a stream from server to client, using event-stream (specifically the results of a block-chain query). I am getting unexpected results in the browser console..

    var io = require('socket.io')(server);
    var dsteem = require('dsteem')
    var es = require('event-stream') 
    var util = require('util')
    var client = new dsteem.Client('https://api.steemit.com')
    var stream = client.blockchain.getBlockStream()

/* This sends results to stdout, fine
io.on('connection', function(socket){
    stream.pipe(es.map(function(block, callback) {
        callback(null, util.inspect(block) + '\n') 
    })).pipe(process.stdout);

    // And this sends a simple object to the client 
    socket.emit('blockchainOps', {"Foo!":"Doo!"} );
});
*/

// Putting both together sends strange connection data to client
io.on('connection', function(socket){

        socket.emit('blockchainOps', function() {

            stream.pipe(es.map(function(block, callback) {
                callback(null, util.inspect(block) + '\n');
            }))
        })

    });

What I get in the client console appears to be some kind of TCP socket function,

ƒ (){if(!n){n=!0;var r=a(arguments);u("sending ack %j",r),e.packet({type:i.ACK,id:t,data:r})}}

Can anyone help me understand what's going on and what I'm doing wrong?

== EDIT UPDATE ==

As suggested in comments, I've tried socket.io-stream to augment event-stream.

var es = require('event-stream') 
var util = require('util')
var ss = require('socket.io-stream'); 
var stream = ss.createStream();

io.on('connection', function(socket){

ss(socket).emit('blockchainOps', stream, function(){


        client.blockchain.getBlockStream()
            .pipe(es.map(function(block, callback) {
                callback(null, util.inspect(block) + '\n') 
                }))
            .pipe(process.stdout)


}());

});

This time I get a socket object returned in the browser console which does not seem to be the stream data I was hoping for.

回答1:

You're using socket.emit wrong, you're passing the ACK callback to the client instead of your stream. Have a look at socket.emit signature :socket.emit(eventName[, ...args][, ack]).

You probably want something like

socket.emit('blockchainOps', client.blockchain.getBlockStream());

However, I don't think plain socket io supports passing a Stream like that. To pipe a stream down to the client you could use socketio-stream. It would look like this:

var ss = require('socket.io-stream');
var stream = ss.createStream();

ss(socket).emit('blockchainOps', stream);
client.blockchain.getBlockStream().pipe(stream);

EDIT:

On the client, you should be able to read your stream like this:

    <script src="socket.io/socket.io.js"></script>
    <script src="socket.io-stream.js"></script>
    ...
    ss(socket).on('blockchainOps', function(stream) {
       var binaryString = "";

       stream.on('data', function(data) {
           for(var i=0;i<data.length;i++) {
                binaryString+=String.fromCharCode(data[i]);
           }                
       });

        stream.on('end', function(data) {
             console.log(binaryString);
             binaryString = "";
       });
    });

来源：https://stackoverflow.com/questions/48627210/how-to-stream-data-over-socket-io-to-client

标签

node.js

sockets

Socket.IO

event-stream