The fundamental part of ActivityPub federation is the "actor", or in Mastodon terms, the account. Accounts from other servers are queried and saved into the local database to allow sending and receiving interactions. The ResolveRemoteAccountService
class is responsible for this, working in two steps: Converting a human-readable handle like username@domain into URLs to the remote account's resources via Webfinger, and then using the linked remote account's JSON representation to create a local mirror.
Step 1: Webfinger
% curl -i "https://counter.social/.well-known/[email protected]"
HTTP/1.1 200 OK
Date: Thu, 04 Jan 2018 03:29:01 GMT
Content-Type: application/jrd+json; charset=utf-8
Transfer-Encoding: chunked