Windows 8 / WP8 - send issue

[iw1qlh]

I am trying to send a string on Windows 8 / WP8

window.tlantic.plugins.socket.send(
        function () { },
        function () { console.log("send failed") },
        connectionId,
        "IW1QLH" + String.fromCharCode(13)
        );

Like you can see in the image (payload is highligthed), extra bytes are added to the begin of the string (they seem the string length):

This is the same string (without CR) sent using a telnet program, no extra bytes are added