FrameMaker 2015 Script - Retrieved UTF-8 strings are stored as ANSI - Japanese Char

Dear community,

I retrieve some strings from a *.txt file over a local network, and later store those into the variables of a *.fm file.

The *.txt file is UTF-8 encoded. However, the UTF-8 encoding changes to ANSI, the characters change e.g. from "面の定義" to "面の定義"

I don't understand why the encoding changed.

How can I encode the ANSI string back to UTF-8?

Thanks!

function GetProp(doc, information) {
    var conn = new Socket;
    if (conn.open ("localhost:8000", "UTF-8")) {
        var getRequest = "GET /workbench/" + doc + "/" + information + "/ HTTP/1.1\r\nHost: localhost\r\n\r\n";
        conn.encoding = "BINARY"; //this line does not seem to have impact
        conn.write(getRequest);
        var endlessLoopCounter = 0;
        var responseHeader = "";
        
        while(responseHeader.substring(responseHeader.length - 4, responseHeader.length) != "\r\n\r\n") {
            responseHeader += conn.read(1);
        }    
        var contentLength = 0;        
        var index1 = responseHeader.toLowerCase().indexOf("content-length:");
        var index2 = responseHeader.toLowerCase().indexOf("\r\n", index1);
        if(index2 < 0) responseHeader.toLowerCase().indexOf("\n", index1);
        if(index1 > -1) {
            contentLength = parseInt(responseHeader.substring(index1 + 15, index2));
        }
//here starts the reading
        var content = "";
        for(var i = 0; i < contentLength; i++) {
            content += conn.read(1);
        }      
        conn.close();
       return content;
  }
  return "error";
}