Pingbacks or Trackbacks are a method for automatically linking websites using XML-RPC requests. Wordpress can do this via HAUS, and clearly Drupal can too, as they both support XML-RPC, so which one should you go with? There are two modules. One is Trackback, which manages incoming trackbacks in it's own way. Personally, I don't like this approach very much, because the data is difficult to grasp, the module doesn't support Views yet and you're left on your own to fight spam. Frankly, there's not a lot going on in this module.
Pingback Module
Of more interest here is the Pingback Module. This writes and sends the Pingbacks as comments.The settings are a little tricky at first. When you install the module, it doesn't seem to do anything. Before you can start, you have to create an input format for the Pingback comments. These formats have to be accessible to anonymous users, according to XML-RPC Specifications. You then adjust the Pingback and other settings, as shown in the illustration below.
Input Format
Pingback needs a special input format. Why that is I couldn't tell you yet, as I haven't looked into the module in great detail. So I created a simple one. Which is important - so you avoid making a mistake like switching all the filters off. Initially, I thought the best thing to do would be to have a format that didn't have any filters at all. But that just leaves the back door wide open to spammers. Aside from a description, the Pingback format needs to be easy, to handle the comments as Pingback. So always ensure the HTML Filter and the HTML CleanUp are on. Just to be on the safe side.
Hide pingback input format for anonymous users
If you use this option, how can anonymous users write in this format? The problems is this - when you use the great Better Formats Module, you can still see all the formats. It doesn't matter though, because I recommend using Better Formats, then the choice of formats is taken away from anonymous users altogether. In this way, they'll always have to write in Filtered HTML, and that's exactly what we want, rather than overwhelming them with incomprehensible options.
Receive Pingbacks
This is one we'll all probably want. It brings, via XML-RPC requests, new comments about our sites from other sites which support the same protocol. But beware! Spammers know all about this and naturally just use the same protocol. So we have to moderate all the comments, for example, by using Mollom. Moderating is irritating; comments are always mixed, and Mollom often rejects positive comments as well as negative. Captcha, here of course, is not an alternative. It would be great if this module just entered comments as unpublished data, and we only had these to moderate.
Pingback Auto-Ping
This feature is one we should all enable as an absolute must. So we can ping any URLs in our online articles. This can be achieved by ##### or via Cron. Cron seems to have both longstanding Faults and to prevent Cron Jobs running at all. Judging from my own test results, this works very well, even "When creating and updating nodes". If you choose this module, you'll have something that works with Drupal, that works with Wordpress, and is of a similar standard.
It's a shame that the module is poorly maintained and unsexy, and we're confined to a small section of the Bloggosphere. But I have faith in it, and hopefully will have a little time to write a few patches.
