Messages¶

Commands like DEM_Packet, DEM_SignonPacket, and DEM_FullPacket contain an inner stream of service messages. These are the actual game state updates.

Packet Structure¶

Inside a CDemoPacket.data (or CDemoFullPacket.packet.data) payload, messages are packed sequentially as:

[Msg Type]  ubitvar  — service message enum value
[Msg Size]  varint32 — message body size
[Msg Data]  bytes    — protobuf message

This inner stream is read with a bit reader since ubitvar is a variable-length bit encoding.

Service Message Types¶

Message	Description
`SVC_ServerInfo`	Server configuration, including `tick_interval`
`SVC_CreateStringTable`	Defines a new string table
`SVC_UpdateStringTable`	Delta update to an existing string table
`SVC_PacketEntities`	Entity create / update / delete deltas

`SVC_ServerInfo`¶

Provides the tick interval (typically 1/30 ≈ 0.0333 seconds), which is used to convert simulation time values stored as tick counts back into seconds.

`SVC_CreateStringTable` / `SVC_UpdateStringTable`¶

See String Tables.

`SVC_PacketEntities`¶

The most important message type. It carries a bit stream of entity state changes (creates, updates, and deletes). See Entities for details on how this is decoded.

Compression¶

Both the outer command body and inner string table data can be Snappy-compressed. The command-level compression is indicated by the DEM_IsCompressed flag. String table data has its own compression flag in the CsvcMsgCreateStringTable message.