[zeromq-dev] Sending image file in chunks on push-pull socket

[Supraja Jayakumar]

Hi Kevin

Thank you for replying. I did send a detailed message a few days back but
did not get any response.

The message was as follows:

I am sending an image file from 0mq server to 0mq client in 1024 byte
chunks using pull-push socket. On the client side, i append the chunk to a
string named chunks. It is simply initilaized like var chunks='' and reset
to empty string on every new request. On receiving a 'success' message in
the 'res' socket in the client side, the chunks data structure is written
to a png file.

But on the client side, i see that even before any incoming data is
appended to chunks, the size of chunks is always between 1-20 bytes. Why is
this ?

Also, the incoming message size should be only 1024 bytes. But i get
smaller or larger incoming chunks. Why is this ?

On server side, i do:

size = getFilesizeInbytes(obj.file);                    // get the size of
the file
buf  = fs.readFileSync(obj.file);                       // get the file in
a buffer
var i=0;var j=i+1024;
while (i < size){                                   // WHILE(){ the send
loop }
if (j < size){
sendingBuff = buf.toString().substring(i,j);
push.send(sendingBuff);
console.log('Sent file part ' + i + ' to ' + (j-1));
i = i + 1024;
j = i + 1024;
}
else{
j = size;
sendingBuff = buf.toString().substring(i,j);
push.send(sendingBuff);
console.log('Sent file part ' + i + ' to ' + (j-1));
i = size + 1;
rp.send('success');
}
}
}

On client side:

Client.prototype._handleMessageFromPushSocket = function(msg) {
fs.write('img.png', chunks, 'binary', function(err){
if(err) {
console.log(err);
}
console.log('written successfully!');
});
};

On recieving the 'success' message from server on the 'req' socket, we do:

if(response_message=='success') {
fs.writeFile('out.png', chunks, 'binary', function(err) {
if(err) throw err;
console.log('Image written');
});
}

Update: Incoming msg length becomes zero towards the end of the transfer.
It seems this maybe a known issue as noted here ? -
http://stackoverflow.com/questions/38420559/receiving-0-size-messages-while-using-zmq-and-protobuf?noredirect=1&lq=1

I am using node.js 0mq bindings on windows7 with git bash.

Any help will be appreciated.

Thanks
Supraja J


On Mon, Feb 20, 2017 at 1:27 PM, Kevin Sapper <kevinsapper88 at gmail.com>
wrote:

> Hi Supraja,
>
> without any details I can only point you to the guide
> http://zguide.zeromq.org/page:all#Transferring-Files
>
> //Kevin
>
>
> On Mo, Feb 20, 2017 at 8:46 , Supraja Jayakumar <suprajasankari at gmail.com>
> wrote:
>
> An image file is transferred from zmq server to zmq client through
> push-pull socket chunk by chunk (in 1024 bytes). I do not get the last 9KB
> of any file i send as the incoming message length on the client side zmq
> pull socket is zero!
>
> Plaform: windows/0mq bindings/node.js/visual studio 2015/git bash
>
> Any ideas on how to resolve this will be helpful.
>
> Thanks
>
> Supraja J
> --
> U
>
>
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-- 
U
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