Outgoing friend messages not delivered despite successful protocol implementation

[keithah]

Problem Description

Incoming messages work perfectly, but outgoing friend messages are not delivered to recipients despite implementing both modern unified messaging and legacy protocols with comprehensive debugging.

What Works ✅

• Authentication: Complete Steam Guard login flow
• Incoming messages: Successfully receive messages via ClientFriendMsgIncoming packets
• Friend management: List, add, accept, remove friends all working
• Persona state: Can set and maintain Online status (with PersonaSetByUser=true)
• Client initialization: Full SteamKit-compatible setup with ClientSessionStart handshake

What Doesn't Work ❌

• Outgoing messages: Neither unified messaging nor legacy protocols deliver messages to recipients
• Messages are "sent" without errors but never received by the target user
• Tested with multiple service method names and protobuf encodings

Technical Implementation

Protocols Tested

1. Unified Messaging (FriendMessages.SendMessage#1)

   • Manual protobuf encoding with all required fields
   • Tried multiple service method variations
   • Added client_message_id field matching SteamKit
   • Gets no responses from Steam (tested Job IDs 2-6)

2. Legacy Protocol (ClientFriendMsg)

   • Direct protobuf message with EMsg_ClientFriendMsg
   • Byte-encoded message content (not string)
   • Same approach as SteamKit's SendChatMessage
   • Sends without errors but messages not delivered

Key Enhancements Made

• ClientSessionStart: Added missing critical handshake from SteamKit analysis
• Enhanced login: OS type, machine ID, chat mode, UI mode, package version
• PersonaSetByUser=true: Proper user-initiated persona state changes
• Offline message request: Initialize message delivery system
• Comprehensive debugging: Packet monitoring, job ID tracking, raw data analysis

Debug Evidence

Successful Incoming Message

[DAEMON] 📨 Message from 76561198025077538: test20
🔍 CLIENT DEBUG: Received packet - EMsg: EMsg_ClientFSOfflineMessageNotification (7523)

Outgoing Message Attempts

🐛 DEBUG: Sending unified message - Service: FriendMessages.SendMessage#1, Job ID: 2, Data length: 50
✅ SUCCESS: FriendMessages.SendMessage#1 sent with Job ID: 2
🐛 DEBUG: Using legacy ClientFriendMsg protocol (EMsg_ClientFriendMsg)...
✅ Message sent to Steam servers\!

No responses received for any outgoing message attempts despite comprehensive logging.

Questions

1. Service Authentication: Do unified messaging services require additional authentication that we're missing?

2. Protocol Evolution: Has Steam deprecated certain outgoing message protocols for third-party clients?

3. Client State: Are we missing critical client state initialization that enables outgoing message delivery?

4. Rate Limiting: Could Steam be silently dropping messages due to rate limiting or anti-spam measures?

Environment

• Go Version: 1.24.5
• Platform: macOS (Darwin 24.6.0)
• go-steam Version: Latest (commit a4cfc61)
• Steam Account: Not restricted, can send/receive via official Steam client

Request

Looking for insights on:

• What enables outgoing message delivery in Steam's protocol
• Whether there are additional handshakes or authentication steps required
• If modern Steam has different requirements for third-party clients
• Protocol analysis tools or approaches that could help identify the missing piece

The comprehensive debugging infrastructure is now in place to quickly test any suggested solutions.

References

• Commit: a4cfc61 - Complete implementation with extensive debugging
• All protocols implemented following SteamKit patterns
• Incoming message delivery works perfectly, proving client setup is largely correct