issue in encoding

/**
 * Callback for http_server
 * - it handles the proxying itself
*/
function http_server_cb(request, response){
	// extract path extname for the request url
	var parsedUrl	= require('url').parse(request.url, true);
	var query	= parsedUrl.query;
	var req_url	= query.url;
	// log the event
	console.log("proxy to "+req_url);
	//console.dir(parsedUrl);
	// normal http proxying
	var host_field		= require('url').parse(req_url).host.split(':');
	var proxy		= http.createClient(host_field[1] || 80, host_field[0])
	var proxy_request	= proxy.request(request.method, req_url, request.headers);
	proxy_request.addListener('response', function(proxy_response) {
		proxy_response.setEncoding('utf8');
		// read data from proxy_response and queue them
		var body	= "";
		proxy_response.addListener('data', function(chunk) {
			//console.log("data", chunk.toString('utf8'));
			body	+= chunk.toString('utf8');
		});

		// when proxy_reponse is over
		proxy_response.addListener('end', function() {
			console.log("end of "+req_url)
			if( parsedUrl.pathname == "/feed" ){
				body	= postprocessSpectatorFeed(body);
			}else if( parsedUrl.pathname == "/feedRaw" ){
			}else if( parsedUrl.pathname == "/raw" ){
			}else if( parsedUrl.pathname == "/channels" ){
			}else console.assert(false);
			// handle the jsonp escaping
			if( query.callback ){
				body	= query.callback + "(" + JSON.stringify(body) + ")";
				// update the content-length
				proxy_response.headers['content-type']	= "text/javascript";
			}
			// update the content-length
			proxy_response.headers['content-length']	= body.length;
			// put the header
			response.writeHead(proxy_response.statusCode, proxy_response.headers);
			console.log(body)
			console.log(body.length)
			response.end(body, 'utf8');
		});
	});
	request.addListener('data', function(chunk) {
		proxy_request.write(chunk, 'utf8');
	});
	request.addListener('end', function() {
		proxy_request.end();
	});
}