posts/sending_pingback_oldskool_indieweb.org

   1 #+title: About sending pingbacks, webmentions and some thoughts on how to improve on them.
   2 #+filetags: indieweb blogging open_web
   3 #+date: 2023-10-31T20:41:30+08:00
   4
   5 In a 'blast from the past', I sent my first
   6 [[https://www.hixie.ch/specs/pingback/pingback][pingback]] after writing
   7 the [[previous post|agent based models digital twins]]. A pingback is a
   8 way for a blogger to send a message to another blogger, informing them
   9 they've written a post that refers to theirs, e.g. as a reply or an
  10 extension of the ideas raised.
  11
  12 The process is a bit more involved than using a
  13 [[https://www.w3.org/TR/webmention/][webmention]], which I've used
  14 before and [[implemented support for|Implementing webmention on my
  15 blog]] a while back, due to requiring an XML message to be created
  16 rather than a simple exchange of URLs.
  17
  18 First, I created a file =pingback.xml= containing the URLs of the blog
  19 post I wrote and the one I made reference to within my post. The
  20 standard defines the schema, resulting in the following:
  21
  22 #+BEGIN_SRC XML
  23 <?xml version="1.0" encoding="UTF-8"?>
  24 <methodCall>
  25     <methodName>pingback.ping</methodName>
  26     <params>
  27         <param>
  28             <value><string>https://www.vanrenterghem.biz/blog/posts/agent_based_models_digital_twins/</string></value>
  29         </param>
  30         <param>
  31             <value><string>https://johncarlosbaez.wordpress.com/2023/10/25/software-for-compositional-modeling-in-epidemiology/</string></value>
  32         </param>
  33     </params>
  34 </methodCall>
  35 #+END_SRC
  36
  37 Next, I used =curl= on the command-line to send this file in a POST
  38 request to Wordpress's pingback service. I had to use the =-k= option to
  39 make this work - bypassing verification of the TLS certificate.
  40
  41 #+BEGIN_SRC sh
  42 curl -k https://johncarlosbaez.wordpress.com/xmlrpc.php -d @pingback.xml
  43 #+END_SRC
  44
  45 In a sign things were going well, I saw the following appear in my
  46 website's access log:
  47
  48 #+BEGIN_SRC txt
  49 192.0.112.141 - - [29/Oct/2023:09:35:06 +0100] "GET /blog/posts/agent_based_models_digital_twins/ HTTP/1.1" 200 2676
  50 "https://www.vanrenterghem.biz/blog/posts/agent_based_models_digital_twins/"
  51 "WordPress.com; https://johncarlosbaez.wordpress.com; verifying pingback
  52 from 139.216.235.49"
  53 #+END_SRC
  54
  55 Finally, I received the following response to my =curl= request on the
  56 command-line:
  57
  58 #+BEGIN_SRC XML
  59 <?xml version="1.0" encoding="UTF-8"?>
  60 <methodResponse>
  61   <params>
  62     <param>
  63       <value>
  64       <string>Pingback from https://www.vanrenterghem.biz/blog/posts/agent_based_models_digital_twins/ to https://johncarlosbaez.wordpress.com/2023/10/25/software-for-compositional-modeling-in-epidemiology/ registered. Keep the web talking! :-)</string>
  65       </value>
  66     </param>
  67   </params>
  68 </methodResponse>
  69 #+END_SRC
  70
  71 That "Keep the web talking! :-)" message made me smile.
  72
  73 In order to understand a bit better how things were being processed, I
  74 checked the Wordpress code for its pingback service, and it appears they
  75 [[https://core.trac.wordpress.org/browser/trunk/src/wp-includes/class-wp-xmlrpc-server.php?rev=56637#L7040][take
  76 the title of the linked article as the author]], which seems a bit odd.
  77 The pingback standard didn't allow for anything but the swapping out of
  78 links though. How your reference is summarized on the referred site is
  79 entirely left to recipient - who may process pingbacks manually or use a
  80 service automating (parts of) the processing.
  81
  82 Wordpress processes pingbacks automatically, turning them into comments
  83 on the original post. As the comment text,
  84 [[https://core.trac.wordpress.org/browser/trunk/src/wp-includes/class-wp-xmlrpc-server.php?rev=56637#L7036][Wordpress
  85 uses the link text in the anchor element]] with a horizontal ellipsis
  86 around it, and some filtering to prevent the comment from being too
  87 long. It's odd how the standard didn't define further approaches to make
  88 this a bit easier. A pingback attribute in the anchor element would have
  89 been helpful for instance, as we could put some text in there to
  90 summarise our page when the pingback is processed automatically. Most
  91 surprisingly maybe, with the benefit of hindsight, it would have been
  92 interesting had the subsequent standard that emerged, Webmention,
  93 implemented some further enhancements.
  94 [[https://aaronparecki.com/][Aaron Parecki]], author of the Webmention
  95 W3C Recommendation, might know if that was ever considered, or just not
  96 within the use case for pingbacks / webmentions? There seemed to have
  97 been [[https://aaronparecki.com/2019/10/15/26/][some thought put into it
  98 in 2019]] at least.