I was trying to get org-protocol to work on KDE Plasma 5.4.2. I set up
my ~/.kde/share/kde4/services/org.protocol, but the standard
org-protocol sample syntax:

   org-protocol://store-link://URL/TITLE

resulted in the error:

   Malformed URL
   Port field was empty; source was "..."; scheme = "org-protocol",
   host = "store-link", path = "// ..."

Modifying my Javascript to create links of the form:

   org-protocol://store-link:0//URL/TITLE

made org-protocol correctly pass the link to emacsclient KDE 5.4.2. This
patch allows the optional specification of a port in the URI. What do
you think?