discovery.xml

<?xml version="1.0" encoding="UTF-8"?>
<section anchor="discovery" title="Discovery">
  <t>To be able to connect to a server, the client has to first determine the correct address of the server.
  The server is determined using the domain name of the user name.
  There are two different ways of determining the server address, a DNS based one and by retrieving a JSON object from a "well-known" location.
  The second approach is added as web application clients are unable to perform DNS lookups directly.
  </t>
  <section anchor="discovery-dns" title="DNS">
    <t>The discovery via DNS uses SRV records (<xref target="RFC2052" />).
    Unfortunately, the current format of SRV records is limited as it only includes one transport protocol.
    DNS based discovery is therefore OPTIONAL until we are certain that the defined record format is acceptable.
    </t>
    <t>To discover a WebSocket based FOSP server for wonderland.lit, a DNS lookup for _fosp._wss._tcp.wonderland.lit with the record type SRV hast to be performed.
    Similar, to discover a HTTP based FOSP server, _fosp._https._tcp.wonderland.lit has to be resolved.
    </t>
  </section>
  <section anchor="discovery-well-known" title="Well known">
    <t>When DNS lookups are not possible, the server address can also be discovered by retrieving a JSON object.
    In accordance with <xref target="RFC5785" /> the object MUST be located at https://&lt;domain&gt;/.well-know/fosp.
    A client SHOULD NOT accept this file over plain HTTP.
    </t>
    <t>This response, if successful, MUST contain an JSON object and SHOULD have the "Content-Type" header set to "application/json".
    The object MUST either contain an "https-tcp" attribute with a string value of an valid HTTP URL or a "wss-tcp" attribute with a string value of a valid WebSocket URL or both.
    </t>
  </section>
</section>