Front messages

S2

The protobuf methods and messages StarCraft II uses on Front while signing in.

Every fact on this page comes from one source, so it is all ⚠️ single source until checked against another client or project.

Methods

Direction Service / method Message Purpose
Client → Server ConnectionService / 1 ConnectRequest Opens the RPC session, asking for "bindless" RPC.
Client → Server AuthenticationServer / 1 LogonRequest Starts signing in.
Server → Client ChallengeNotify / 3 ChallengeExternalRequest Sends the client to Blizzard's web sign-in. No response.
Client → Server AuthenticationServer / 7 VerifyWebCredentialsRequest Submits the short-lived credential from the web sign-in.
Server → Client AuthenticationClient / 5 LogonResult The result: account, game accounts, region and a 64-byte session key.
Server → Client AuthenticationClient / 14 GameAccountSelectedRequest Reports which game account was selected.
Client → Server AuthenticationServer / 8 GenerateWebCredentialsRequest Asks for a reusable credential for next time.
Client → Server GameUtilities / 1 ClientRequest Asks for the StarCraft II handoff to Sunken.

AuthenticationClient methods 10 through 14 can arrive as callbacks at any time during sign-in: 10 reports a logon update and 14 the game-account selection. Methods 11 to 13 expect no response.

ConnectRequest

# Field Type
1 client_id ProcessId, optional
2 bind_request BindRequest, optional
3 use_bindless_rpc bool, optional, default true

LogonRequest

# Field Type StarCraft II sends
1 program string S2
2 platform string The platform, such as Mc64 for 64-bit macOS
3 locale string For example enUS
4 email string
5 version string The Battle.net SDK identity built into the game. The exact value for each build is on SC2Docs.
6 application_version int32 0
7 public_computer bool
10 allow_logon_queue_notifications bool, default false
12 cached_web_credentials bytes A reusable credential from an earlier sign-in, if there is one
14 user_agent string
15 device_id string

LogonResult

# Field Type
1 error_code uint32, required
2 account_id EntityId
3 game_account_id repeated EntityId
4 email string
5 available_region repeated uint32
6 connected_region uint32
7 battle_tag string
8 geoip_country string
9 session_key bytes (64 bytes)
10 restricted_mode bool
11 client_id string

Web credentials

Message # Field Type
ChallengeExternalRequest 1 request_token string
2 payload_type string
3 payload bytes
VerifyWebCredentialsRequest 1 web_credentials bytes
GenerateWebCredentialsRequest 1 program fixed32
GenerateWebCredentialsResponse 1 web_credentials bytes
GameAccountSelectedRequest 1 result uint32, required
2 game_account_id EntityId

Two different credentials. The short-lived credential from the web sign-in is used once, with method 7. The reusable credential from method 8 is sent in LogonRequest next time. A client should replace it after every successful use, and fall back to the web sign-in when it's rejected.

The Sunken handoff: ClientRequest

# Field Type StarCraft II sends
1 attribute repeated Attribute The attributes below
2 host ProcessId Omitted
3 account_id EntityId Omitted
4 game_account_id EntityId The first StarCraft II game account from LogonResult
5 program fixed32 Omitted
6 client_info ClientInfo Omitted
Attribute Type Value
LogonTokenRequest string 0.0.1
environment string The region, such as US
session_key blob The 64-byte session key from LogonResult
locale string For example enUS

The response, ClientResponse, is another list of attributes. These carry everything Sunken needs:

Attribute Contents
address The Sunken server's address. The port is 1119 when not given. A bracketed IPv6 address may include a port after the bracket.
session_key Exactly 64 bytes, used for the Resume proof and to derive the encryption keys.
account_region The region number, 0 to 255.
game_account_name, account_mail The account's identity.
logon_response A bit-packed LogonResponse3 with status, timeouts, account data and settings.

Attributes and variants

An Attribute is a name (field 1) and a Variant value (field 2). The Variant field number tells you its type:

# Type # Type
2 bool 7 embedded message
3 signed integer (int64) 8 four-character code
4 double 9 unsigned integer (uint64)
5 string 10 entity ID
6 bytes

Sources and credits

Categories: Battle.net 2.0
Last edited September 16, 2026 by John Leighow.
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