Sessions

An Evennia Session represents one single established connection to the server. Depending on the Evennia session, it is possible for a person to connect multiple times, for example using different clients in multiple windows. Each such connection is represented by a session object.

A session object has its own cmdset, usually the “unloggedin” cmdset. This is what is used to show the login screen and to handle commands to create a new account (or Player in evennia lingo) read initial help and to log into the game with an existing account.

Warning: A Session is not persistent - it is not a typeclass and has no connection to the database. The Session will go away when a user disconnects and you will lose any custom data on it if the server reloads. The .db handler on Sessions is there to present a uniform API, but if you were to read its doc you’ll find it’s actually just an alias to .ndb. So don’t store any data on Sessions that you can’t afford to lose in a reload. You have been warned.

A session object can either be “logged in” or not. Logged in means that the user has authenticated. When this happens the session is associated with a Player object (which is what holds account-centric stuff). The player can then in turn puppet any number of objects/characters.

Multisession mode

The number of sessions possible to connect to a given player at the same time and how it works is given by the MULTISESSION_MODE setting:

  • MULTISESSION_MODE=0: One session per player. When connecting with a new session the old one is disconneted. This is the default mode and emulates many classic mud code bases.
  • MULTISESSION_MODE=1: Many sessions per player, input from each session is treated identically. This means that you could use any number of different clients to input something and all would see the same result back.
  • MULTISESSION_MODE=2: Many sessions per player, one character per session. This is the multi-playing mode where each session may, through one player account, individually puppet its own object/character without affecting what happens in other sessions.
  • MULTIPLAYER_MODE=3: Many sessions per player and character. This is the full multi-puppeting mode, where multiple sessions may not only connect to the player account but multiple sessions may also puppet a single character at the same time. Tt is a multi-session version of mode 1. This allows multiplaying of many characters from any number of clients at once.

Returning data to the session

When you use msg() to return data to a user, the object on which you call the msg() matters. The MULTISESSION_MODE also matters, especially if greater than 1.

For example, if you use player.msg("hello") there is no way for evennia to know which session it should send the greeting to. In this case it will send it to all sessions. If you want a specific session you need to supply its session id (sessid) to the msg call.

On the other hand, if you call the msg() message on a puppeted object, like character.msg("hello"), the character already knows the sessid of the session that controls it - it will cleverly auto-add this for you (you can specify a different sessid if you specifically want to send stuff to another session).

Finally, there is a wrapper for msg() on all command classes: command.msg(). This will transparently detect which session was triggering the command (if any) and redirects to that session (this is most often what you want). If you are having trouble redirecting to a given session, command.msg() is often the safest bet.

You can get the sessid in many ways.

  • A session stores the sessid in a property sessid.
  • The player’s sessions property holds all sessions connected to this player.
  • Puppeted objects (normally Characters) have the persistent sessid property of the session puppeting them.
  • Commands store the sessid pointing back to the session that triggered them (will be None if no session is involved, like when a mob or script triggers the command).

Customizing the session object

When would one want to customize the Session object? Consider for example a character creation system: You might decide to keep this on the out-of-character level. This would mean that you create the character at the end of some sort of menu choice. The actual char-create cmdset would then normally be put on the player. This works fine as long as you are MULTISESSION_MODE below 2. For higher modes, replacing the Player cmdset will affect all your connected sessions, also those not involved in character creation. In this case you want to instead put the char-create cmdset on the Session level - then all other sessions will keep working normally despite you creating a new character in one of them.

By default, the session object gets the commands.default_cmdsets.UnloggedinCmdSet when the user first connects. Once the session is authenticated it has no default sets. To add a “logged-in” cmdset to the Session, give the path to the cmdset class with settings.CMDSET_SESSION. This set will then henceforth always be present as soon as the player logs in.

To customize further you can completely override the Session with your own subclass. To replace the default Session class, change settings.SERVER_SESSION_CLASS to point to your custom class. This is a dangerous practice and errors can easily make your game unplayable. Make sure to take heed of the original and make your changes carefully.

Portal and Server Sessions

Note: This is considered an advanced topic. You don’t need to know this on a first read-through.

Evennia is split into two parts, the Portal and the Server. Each side tracks its own Sessions, syncing them to each other.

The “Session” we normally refer to is actually the ServerSession. Its counter-part on the Portal side is the PortalSession. Whereas the server sessions deal with game states, the portal session deals with details of the connection-protocol itself. The two are also acting as backups of critical data such as when the server reboots.

New Player connections are listened for and handled by the Portal using the protocols it understands (such as telnet, ssh, webclient etc). When a new connection is established, a PortalSession is created on the Portal side. This session object looks different depending on which protocol is used to connect, but all still have a minimum set of attributes that are generic to all
sessions.

These common properties are piped from the Portal, through the AMP connection, to the Server, which is now informed a new connection has been established. On the Server side, a ServerSession object is created to represent this. There is only one type of ServerSession; It looks the same regardless of how the Player connects.

From now on, there is a one-to-one match between the ServerSession on one side of the AMP connection and the PortalSession on the other. Data arriving to the Portal Session is sent on to its mirror Server session and vice versa.

During certain situations, the portal- and server-side sessions are
“synced” with each other:
  • The Player closes their client, killing the Portal Session. The Portal syncs with the Server to make sure the corresponding Server Session is also deleted.
  • The Player quits from inside the game, killing the Server Session. The Server then syncs with the Portal to make sure to close the Portal connection cleanly.
  • The Server is rebooted/reset/shutdown - The Server Sessions are copied over (“saved”) to the Portal side. When the Server comes back up, this data is returned by the Portal so the two are again in sync. This way a Player’s login status and other connection-critical things can survive a server reboot (assuming the Portal is not stopped at the same time, obviously).

Sessionhandlers

Both the Portal and Server each have a sessionhandler to manage the connections. These handlers contain all methods for relaying data across the AMP bridge. All types of Sessions hold a reference to their respective Sessionhandler (the property is called sessionhandler) so they can relay data. See protocols for more info
on building new protocols.