How to stream data over socket.io to client - node.js

Question

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.

Answer 1

If anyone is looking for a working socket.io stream example
// server side
const { pipeline } = require('stream')
const server = require('http').Server().listen(8080)
const io = require('socket.io')(server)
const ss = require('socket.io-stream')
io.on('connection', (socket) => ss(socket).on('stream', (stream) => {
pipeline(stream, process.stdout, (err) => err && console.log(err))
}));
// client side
const client = require('socket.io-client')
const socket = client.connect('http://localhost:8080')
socket.on('connect', () => {
const stream = ss.createStream()
ss(socket).emit('stream', stream)
pipeline(process.stdin, stream, (err) => err && console.log(err))
});

Answer 2

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 = "";
});
});