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P_ChatMessage

Direction: Both (C→S "I'm typing into chat"; S→C "render this colored line") Numeric ID: 16 Server handler: ServerNet.bb:183 Client handler: ClientNet.bb:1213

Purpose

The catch-all text channel. Every user-typed chat line, every slash command, every server-side notification, every BVM Output(...) script line travels on this opcode. The client only renders; the server parses, applies access gates, fans out to the right audience (area / online / party / guild / single-target), and may dispatch script work as a side effect.

There is no sub-code byte at the start of the wire payload. The whole packet is a free-form string. Discrimination happens via two parallel signals:

  • First-character semantics on C→S: / and \ enter the slash-command parser; everything else is general chat.
  • First-byte colour escape on S→C: bytes in [250..254] are rendered as colour escapes; anything else is normal-text body.

Field layout

C → S — "Player typed text"

Offset Width Type Field Notes
1 N String Raw text the user typed No length prefix; M\MessageData$ is the whole payload.

The handler bails immediately if Len(M\MessageData$) <= 0 Or AI = Null (ServerNet.bb:185). After that:

  • Left$(M\MessageData$, 1) = "/" Or Left$(M\MessageData$, 1) = "\" → strip the leading char, split on first space, Command$ = Upper$(...), dispatch into the giant Select Command$ (ServerNet.bb:187-693).
  • Otherwise → general chat: prepend "<" + AI\Name$ + "> ", broadcast over the per-area FirstInZone chain, log to ChatLog per ChatLoggingMode (ServerNet.bb:694-712).

S → C — "Render this line with colour"

Offset Width Type Field Notes
1 1 Byte Colour escape (optional) One of 250..254, or any other byte → start-of-normal-text.
2 3 Byte×3 R, G, B Only present when offset 1 = 250. Each in [0..255].
2 or 5 N String Message body Rendered through Output(...) or BubbleOutput(...).

Colour-escape semantics (ClientNet.bb:1215-1227):

Prefix RGB Channel / use
Chr$(254) 255, 255, 0 (yellow) System / GM / party-join / time-of-day / invite — server-authored notifications.
Chr$(253) 255, 50, 50 (red) Yell, error, ignore confirmation, ability-not-recharged.
Chr$(252) 200, 10, 200 (magenta) /me emote, /pm private-message, NPC→player chat ("Player: ...").
Chr$(251) 20, 220, 50 (green) Guild chat, party chat.
Chr$(250) (next 3 bytes) Custom RGB. Primary emitter is BVM_OUTPUT(actor, text, R, G, B) at ScriptingCommands.bb:2793; engine also uses it for the critical-damage notification at three sites in GameServer.bb (Chr$(255) + Chr$(225) + Chr$(100) — peach/orange).
other (default) Normal text. If body starts "<NAME> " and UseBubbles > 1, renders as a 3D chat bubble above the named actor.

The chat-bubble path (ClientNet.bb:1231-1254) only fires for the no-escape case — coloured lines never get bubbles. Bubble lookup goes through FindPlayerFromName(...); if no actor matches, the line falls back to normal text output.

C → S slash-command catalog

The dispatch is a single Select Command$ keyed on LanguageString$(LS_SC*) (Language.bb) — nearly every command is localizable. The two exceptions are /help and /?, which are hardcoded at ServerNet.bb:680 (Case "HELP", "?") pending an LS_SCHelp entry. Below uses the English defaults.

Command Gate Effect
/kick <name> DM Sends RCE_PlayerKicked + P_KickedPlayer to target.
/ignore <name> / /unignore <name> none Mutates the inviter's Account\Ignore$ CSV.
/me <text> none Area broadcast with Chr$(252) + "* " + Name + " " + text.
/yell <text> none Server-wide broadcast (walks FirstOnlinePlayer chain).
/g <text> guild member Walk FirstOnlinePlayer, send to same-TeamID.
/p <text> party member Walk Party\Player[0..7].
/pm <name>, <text> none Walk FirstOnlinePlayer, deliver to first matching name.
/invite / /accept / /leave none Party state machine.
/pet <name>, <cmd>, <args> own a pet Walk AI\FirstSlave chain; dispatch CommandPet(...).
/trade <name> none Player→player trade offer.
/players / /allplayers none Counter — current area vs. server-wide.
/time / /date / /season none Game-clock report.
/warp <area>[,<instance>] DM Self-warp to the area's first defined portal (the Instance arg picks the area-instance, not coordinates).
/warpother <name>, <area>[,<instance>] DM Warp another player to the area's first defined portal.
/xp <amount> DM GiveXP(AI, n).
/gold <amount> DM Direct gold adjustment + P_GoldChange.
/setattribute <attr>, <n> / /setattributemax <attr>, <n> DM Calls UpdateAttribute / UpdateAttributeMax for Health/Speed/Energy, otherwise writes through and broadcasts P_StatUpdate.
/script <name>, <func> DM Spawns a ThreadScript(...) with privileged=1 — the script can call any privileged BVM.
/gm <text> DM Broadcast to all DMs only.
/ability / /give / /weather / /netdump DM Misc DM tools.
other none Falls through to the ScriptExists%("In-game Commands") hook → ThreadScript("In-game Commands", Command$, ..., Params$), otherwise replies "Unknown command:" (ServerNet.bb:688-692).

/help [topic] is special: it emits one P_ChatMessage per line of help text, all prefixed Chr$(254). The entry point SendChatHelp lives at ServerNet.bb:31-60; the per-topic detail dispatcher SendChatHelpDetail at ServerNet.bb:65-109. The DM-only summary block at ServerNet.bb:57-58 is gated by the same Account\IsDM check.

Validation requirements

C → S handler (ServerNet.bb:183-712)

The packet body is free-form, so length / shape gates are minimal. The defences live in the per-command logic:

  1. Sender validity: AI = FindActorInstanceFromRNID(M\FromID); bails on Null.
  2. Non-empty body: Len(M\MessageData$) > 0.
  3. Account-Null discipline: every DM-gated command does A.Account = Object.Account(AI\Account) : If A <> Null And A\IsDM = True. The A <> Null check is load-bearing — a mid-logout account that has been Deleted but whose Handle is still on AI\Account returns Null from Object.Account(...), and bare A\IsDM would crash the server from a chat command (see audit-comment at ServerNet.bb:200-202). Apply this to every new /command that needs a DM gate — the pattern is non-negotiable.
  4. /pet chain walk: walks AI\FirstSlave / NextSlave (ServerNet.bb:266-273) — the per-leader chain that PR #287 introduced, replacing a global Each ActorInstance scan.
  5. /yell / /g / /gm / /pm / /allplayers chain walks: walk FirstOnlinePlayer / NextOnlinePlayer (ServerNet.bb:408-462) — the engine-wide players chain (PR #288 era). Filters that used to require If A2\RNID > 0 are gone because the chain only contains online players.
  6. Mid-warp AreaInstance guard: /me, /players, and the general-chat fallback all do AInstance.AreaInstance = Object.AreaInstance(AI\ServerArea) : If AInstance <> Null Then ... — soft-fails when the actor is in the brief window between SetArea rebinding zones. The chat line just doesn't broadcast that tick; no crash.
  7. PlayerIgnoring filter: every fan-out skips recipients whose ignore-list contains the sender (ServerNet.bb:394 / 410 / 457).

Privilege classification

The DM gate is not the BVM RequirePrivileged() gate. Slash commands are dispatched directly from the packet handler — they never enter the BVM, so BVM_RequirePrivileged is irrelevant here. The Account\IsDM boolean is the only check. Two notes:

  • /script spawns with privileged=1 (ServerNet.bb:385) — this is the only path from chat that lets a script call privileged BVMs (Ban/Kick/Warp/CreateUDPStream/etc.). The DM gate is what authorises the elevation; downstream BVMs check the privileged bit on ScriptInstance.
  • Unknown commands fall through to "In-game Commands" (ServerNet.bb:688-692) — these scripts are spawned with the default (un-privileged) flag. Content authors who want player-facing slash commands should put them there; only the engine's DM-only set should ever reach the privileged=1 path.

S → C emit pattern

Every RCE_Send(Host, target_rnid, P_ChatMessage, Pa$, True) follows the same shape: the colour-escape byte (or none) is the first character of Pa$. Recipients:

  • Self-only notifications (errors, confirmations, /players results) — sent to AI\RNID.
  • Area broadcast (/me, general chat) — walks AInstance\FirstInZone chain, sends per actor with RNID > 0.
  • Server-wide broadcast (/yell, /gm, /g) — walks FirstOnlinePlayer chain.
  • Party broadcast (/p, party-join notification) — For i = 0 To 7 : Party\Player[i] array.
  • Single target (/pm, /invite, /trade) — direct send to the resolved target's RNID.

The general-chat fallback at ServerNet.bb:705-710 also adds the line to the server's Game\ChatText ListBox (for the dedicated-server console) and writes it to ChatLog when ChatLoggingMode > 0.

Anti-cheat surface

P_ChatMessage is not the high-stakes packet P_AttackActor is, but it has the largest privilege surface of any packet because of /script. The defences:

  • Wire payload is text, not opcode — a malformed packet can produce a garbled chat line but cannot reach /script unless the sender has IsDM on their account.
  • DM bit is server-side only — clients cannot fabricate IsDM; it lives on the Account row in MySQL / accounts.dat.
  • Privileged spawn is gated on DM bit — losing DM in the middle of /script would not retroactively un-privilege a running script; the bit is captured at spawn. That's fine — administering a DM-set should be done in a separate channel anyway.
  • Soft-fail on every Account-Null path — the A <> Null checks ensure a mid-logout DM cannot crash the server by typing into chat as the account is being freed.

Historical bugs / PR references

PR Fixed
Audit pre-PR Account\IsDM reads after Object.Account(...) did not check Null first — server-crash via slash command from a mid-logout DM. Audit-comments at ServerNet.bb:200-202 / 220-221 / 237 record the pattern.
#287 /pet walks the per-leader FirstSlave chain (replacing global Each ActorInstance scan).
#288 and predecessors /yell / /g / /gm / /pm / /allplayers walk the FirstOnlinePlayer chain.
PRs #154 / #155 / #176 / #182–#188 Object.AreaInstance(...) Null discipline sweep — covers /me, /players, and general-chat fallback paths.
Unknown-command notify Pre-fix, an unknown slash command silently no-op'd. Now replies "Unknown command: /xxx. Type /help for a list." (ServerNet.bb:691).

Related packets

  • P_StandardUpdate — Chr$(254) system lines often follow a warp; the warp itself rides P_StandardUpdate.
  • P_AttackActor — /kick is the chat-equivalent of forcibly removing an actor; combat is the other way out.
  • P_GoldChange — /gold emits this directly; the chat line is just confirmation.
  • P_KickedPlayer — paired with /kick to actually disconnect the target.

See also