HL Protocol

Hotline Protocol

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Core Documentation

• Documentation Home
• Glossary / Terms
• Protocol History

Technical Specifications

• Transaction IDs
• Field Definitions
• Access Bits
• Error Codes

Binary & Data

• FILP/RFLT Specs
• News Headers
• Logic Sequences

External Networking

• Tracker (HTRK)
• HTTP Tunneling
• Global Server

Assets

• Icon Gallery

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Hotline Network Protocol – Version 1.9

Property of Hotsprings Inc. Publicly licensed under the GPL

Introduction

Hotline client is an application providing user interface for end-user services (chat, messaging, file services and other). Hotline server provides services and facilitates communication between all clients.

Port Assignments

Additional port numbers are determined by using the base port number:

Port	Usage
Base port	Regular transactions
Base port + 1	Upload/download
Base port + 2	HTTP tunneling for regular transactions
Base port + 3	HTTP tunneling for uploads/downloads

Note: Numeric data is always in network byte order (big-endian).

Technical Documentation Index

Core Protocol

• Transactions – The master list of all 411 Transaction IDs and their constants.
• TransactionFields – Detailed list of Field IDs (100–337) and data types.
• AccessPriviledges – The 64-bit access privilege bitmap breakdown.
• TransactionSequence – Logic for Login and Invite-to-Chat sequences.

Data Structures

• BinaryStructure – Details on the Flattened File Object (FILP) and Resume data (RFLT).
• NewsStructure – Binary headers for news categories, articles, and posters.

External Interfaces

• TrackerInterface – How servers register with and clients query the Tracker (HTRK).
• HTTPTunneling – Encapsulation logic for GET/POST proxy traversal.
• GlobalServerTransactions – Management and querying of the Global Server database.

Session Initialization

After establishing TCP connection, both client and server start the TRTP handshake.

Client Request

Description	Size	Data	Note
Protocol ID	4	'TRTP'	0x54525450
Sub-protocol ID	4		User defined
Version	2	1	Currently 1
Sub-version	2		User defined

Server Reply

Description	Size	Data	Note
Protocol ID	4	'TRTP'	0x54525450
Error code	4		0 = no error