function handleRequest(request, response) { response.setHeader("Content-Type", "text/plain; charset=ISO-8859-1", false); const body = [0xc1]; var bos = Components.classes[ "@mozilla.org/binaryoutputstream;1" ].createInstance(Components.interfaces.nsIBinaryOutputStream); bos.setOutputStream(response.bodyOutputStream); bos.writeByteArray(body); }