I have written a simple TCP server on node.js to send some data to a Chrome app. In the chrome app, when I get the data, I convert that to string using below function, I get an exception "byte length of Uint16Array should be a multiple of 2"
String.fromCharCode.apply(null, new Uint16Array(buffer))
I could not find any information about what could be causing this and how to fix this. Any pointers on this is highly appreciated.
Below is the code in node.js server for sending the data to client:
socket.on('data', function(data) {
console.log('DATA ' + socket.remoteAddress + ': ' + data);
// Write the data back to the socket,
// the client will receive it as data from the server
var r= socket.write('from server\r\n');
});
Below is the code from chrome app:
chrome.sockets.tcp.onReceive.addListener(function (info) {
console.log('onListener registered');
if (info.socketId != socketid)
return;
else {
try {
data = ab2str(info.data);
console.log(data);
}
catch (e) {
console.log(e);
}
}
// info.data is an arrayBuffer.
});
function ab2str(buf) {
return String.fromCharCode.apply(null, new Uint16Array(buf));
}
You're probably seeing this problem because your app has received an odd number of bytes on the socket, but you're trying to create an array of 2-byte-wide items out of it (because that's what fits into a Uint16Array)
If your app receives the string "Hello" over the network (5 bytes), then you can cast that to a Uint8Array, and it will look like this:
Item: 0 1 2 3 4
Char: H e l l o
Uint8 Value: 72 101 108 108 111
casting it to an Uint16Array, though will try to do this:
Item 0 1 2
Chars He ll o?
IntVal 25928 27756 ?????
Without a 6th byte to work with, it can't construct the array, and so you get an exception.
Using a Uint16Array for the data only makes sense if you are expecting UCS-2 string data on the socket. If you are receiving plain ASCII data, then you want to cast that to a Uint8Array instead, and map String.fromCharCode on that. If it's something else, such as UTF-8, then you'll have to do some other conversion.
No matter what, though, the socket layer is always free to send you data in chunks of any length. Your app will have to deal with odd sizes, and save any remainder that you can't deal with right away, so that you can use it when you receive the next chunk of data.