Chat gateway (telnet)

CHAT

A plain-text way into Battle.net chat, used by early bots and by people with a telnet program. Retired by Blizzard in 2005.

This protocol is historical. Blizzard deprecated the chat gateway in 2005 and later turned it off: official servers now disconnect any client that sends its protocol byte. Community servers may still offer it.

The chat gateway let anything that could open a TCP connection and send lines of text join Battle.net chat, with no game, CD key or version check. It could only chat. See Chat gateway: logon for the handshake step by step.

Starting a session

  1. Connect to TCP port 6112 and send the byte 0x03. Some servers also accept a lowercase c (0x63).
  2. Send the byte 0x04 followed by CR LF to begin logging on.
  3. The server asks for the account name, then the password. Both are sent as plain text, each ending with CR LF.

The password travels unencrypted. The server lowercases it before checking, which matches what the game clients do before hashing.

Rules for gateway users

  • Users appear with the CHAT product and always carry the No UDP flag (0x10).
  • They can't create or join games.
  • On official Battle.net they could only enter a few public channels: Blizzard Tech Support, Open Tech Support, Public Chat and The Void.
  • Other users' statstrings aren't sent, so there are no icons, records or characters.
  • Sending a binary game message over the gateway got the connection closed and the address briefly banned.

Message format

Every line the server sends has the form:

<id> <NAME> <data>
  • id is four decimal digits.
  • NAME is a word that repeats the meaning of the id. It can be ignored when parsing.
  • data may contain spaces. When a message has no data, there's no space after the name.
  • User flags appear as four hexadecimal digits, such as 0010.
  • Product codes appear forwards (STAR), not reversed as in binary messages.
  • Quoted messages are not escaped. The quotes are simply decoration and can be removed.

How the ids are numbered

The ids mirror the binary protocol:

  • 1000 plus a chat event ID, written in decimal, is a chat event. EID_INFO is 0x12, which is 18, so an information message is 1018.
  • 2000 plus a BNCS message ID, written in decimal, is a converted game message. SID_ENTERCHAT is 0x0A, which is 10, so the unique-name message is 2010.

Messages

Id Name Data Binary equivalent
1001 USER <name> <flags> [<product>], one per user already in the channel EID_SHOWUSER
1002 JOIN <name> <flags> [<product>], a user joined EID_JOIN
1003 LEAVE <name> <flags>, a user left EID_LEAVE
1004 WHISPER <name> <flags> "<text>", a whisper to you EID_WHISPER
1005 TALK <name> <flags> "<text>", another user spoke. Your own messages are not echoed back. EID_TALK
1006 BROADCAST "<text>", a server announcement, with no user name EID_BROADCAST
1007 CHANNEL "<channel>", you entered a channel. Channel flags aren't included. EID_CHANNEL
1009 USER <name> <flags> [<product>], a user's flags changed EID_USERFLAGS
1010 WHISPER <name> <flags> "<text>", your whisper was sent. When whispering friends, the name is your friends, which contains a space. EID_WHISPERSENT
1018 INFO "<text>", information from the server EID_INFO
1019 ERROR "<text>", an error from the server EID_ERROR
1023 EMOTE <name> <flags> "<text>", an emote, including your own EID_EMOTE
2000 NULL none. Sent about every 30 seconds while idle. SID_NULL
2010 NAME <name>, your unique name in chat, such as JoeUser#2 SID_ENTERCHAT

The square brackets around the product are part of the message.

Sending

After logging on, every line the client sends is handled exactly like the text of SID_CHATCOMMAND: plain text talks in the channel, and lines starting with / are commands. Text sent without a line ending is joined to the next line.

Staying connected

The server sends 2000 NULL about every 30 seconds of inactivity, but official Battle.net never disconnected gateway users for being idle. Many gateway bots still sent a harmless command such as /time now and then to keep the connection active.

How servers handle the gateway

A server that offers the gateway reads line by line, not byte by byte, and must cap line length so an endless line can't exhaust its memory. It should also accept a bare LF line ending, which bots written on Unix systems often send. Command Center's gateway currently greets the client and handles lines, and is being extended toward full chat.

Sources and credits

This page is written in our own words. BNETDocs is credited for its research; none of its text is copied. See Credits.

Categories: Classic Battle.net | Historical
Last edited September 16, 2026 by John Leighow.
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