response.writeHead(statusCode[, statusMessage][, headers])
Sends a response header to the request. The status code is a 3-digit HTTP status code, like 404. The last argument, headers, are the response headers. Optionally one can give a human-readable statusMessage as the second argument.
Example:
var body = 'hello world';
response.writeHead(200, {
'Content-Length': body.length,
'Content-Type': 'text/plain' });
This method must only be called once on a message and it must be called before