janos erdelyi

i’ve been wanting to use this blog for discussions about technology, programming specifically, though it’s obvious i just like to blather as well.

so here’s my first snippet.

this is the Trackback Ping i use for this site. It’s nothing fancy, and it could probably use some cleanup, but i’m posting nonetheless.

here goes:

public string SendTrackbackPing(
	string pingUrl,
	string url,
	string title,
	string exerpt,
	string blogName
) {
	//validate that we at least have the url
	//much more could be done to verify a proper url format, but if it's bad, it'll just fail
	//garbage in, garbage out.
	if (url == null) {
		throw new Exception("A url is required to send a trackback ping.");
	}
	if (pingUrl == null) {
		throw new Exception("A ping url is required to send a trackback ping.");
	}
	
	
	//build the form data
	//example: title=Foo+Bar&url=http://www.bar.com/&excerpt=My+Excerpt&blog_name=Foo
	StringBuilder sb = new StringBuilder();
	sb.Append("url=");
	sb.Append(encode(url));
	sb.Append("&");
	
	if (title != null) {
		sb.Append("title=");
		sb.Append(encode(title));
		sb.Append("&");
	}
	
	if (exerpt != null) {
		sb.Append("exerpt=");
		sb.Append(encode(exerpt));
		sb.Append("&");
	}
	
	if (blogName != null) {
		sb.Append("blog_name=");
		sb.Append(encode(blogName));
		sb.Append("&");
	}
	
	//post to the pingUrl
	HttpWebRequest httpRequest = (HttpWebRequest)WebRequest.Create(pingUrl);
	httpRequest.ContentType = "application/x-www-form-urlencoded";
	httpRequest.Method = "POST";
	
	byte[] postByteArray = Encoding.ASCII.GetBytes(sb.ToString());
	httpRequest.ContentLength = postByteArray.Length;
	
	Stream stream = httpRequest.GetRequestStream();
	stream.Write(postByteArray, 0, postByteArray.Length);
	stream.Close();
	
	//get a response. it <strong>should</strong> be an xml reponse
	HttpWebResponse httpResponse = null;
	try {
		httpResponse = (HttpWebResponse)httpRequest.GetResponse();
	} catch (Exception oops) {
		//int code = (int) httpResponse.StatusCode;
		throw new Exception("Unable to connect to '" + pingUrl + "'. " + oops.ToString());
	}
	StreamReader responseStream = new StreamReader(httpResponse.GetResponseStream(), System.Text.Encoding.GetEncoding(1252));
	
	string response = responseStream.ReadToEnd();
	
	responseStream.Close();
	httpResponse.Close();
	
	//alrighty, i need to parse the response. it's xml.
	//i could ignore that and just do some regex
	//or i could accept it and do xpath
	
	//i think regex will be lighter
	string errorCode = null;
	string errorMessage = null;
	
	Regex responseReg = new Regex(@"<error>(?<errorcode>\d{1})</error>", RegexOptions.IgnoreCase);
	if (responseReg.IsMatch(response)) {
		errorCode = responseReg.Match(response).Groups["errorcode"].Value;
	}
	
	
	if (errorCode == null) {
		return "Error: \n\n" + response;
	}
	
	if (errorCode == "0") {
		responseReg = null;
		return "success";
	} else {
		responseReg = new Regex(@"<message>(?<errorMessage>[\w\W]*)</message>", RegexOptions.IgnoreCase);
		if (responseReg.IsMatch(response)) {
			errorMessage = responseReg.Match(response).Groups["errorMessage"].Value;
		}
	}
	responseReg = null;
	
	if (errorCode != "0" && errorMessage == null) {
		throw new Exception("Error parsing response from trackback ping: Unable to determine error message.");
	}
	
	return errorMessage;
}

//encode strings for a happy POST
private string encode(
	string input
) {
	if (input  null || input  "$4") {
		return "";
	}
	
	string newValue = input.Replace("\"", "'");
	newValue = System.Web.HttpUtility.UrlEncode(newValue);
	newValue = newValue.Replace("%2f", "/");
	return newValue;
}

i call it from my article edit screen via ajax, but it could just as well be called from a regular form post, or from some other method if you like.

soak it in. use it as you want.

i’m going on vacation for a few days, so if you post, it won’t show on the site until i get back to moderate, but it won’t be lost.

some time after i return, i’ll post Part 2, which will be the Trackback receiver, for lack of a better term.

enjoy.

UPDATE – Part 2 has been published.