Signal Server Project Structure

The server-side backend for the Signal messaging app. A focused, high-performance Java application using the Dropwizard framework and Protocol Buffers.

Updated 2025-12-30

#signal #java #dropwizard #protobuf #messaging #security

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Project Directory

Signal-Server/

service/

Main Application Logic

src/main/java/

Core Java source

config/

YAML configuration files

pom.xml

websocket-resources/

Real-time Messaging (WebSockets)

integration-tests/

End-to-end server tests

api-doc/

API documentation source

pom.xml

Root Maven Config

mvnw

Maven wrapper

Repository Info

Repository-signalapp/Signal-Server
Stars-15k+
License-AGPL-3.0
Last Analyzed-December 2025

Tech Stack

Language-Java 21
Framework-Dropwizard (Jetty/Jersey/Jackson)
Serialization-Protocol Buffers
Database-PostgreSQL / FoundationDB
Build Tool-Maven

Architecture Notes

Signal Server is built using the **Dropwizard** framework, which prioritizes stable, battle-tested libraries over 'magic'. The architecture is highly optimized for message delivery. It uses **Protocol Buffers** for efficient serialization across the wire. A key architectural split is between the standard REST services and the websocket-resources, which manage the long-lived connections required for real-time message pushing.

Key Directories

service/-Contains the bulk of the application code, including account management, key fetching, and message routing logic.
websocket-resources/-A specialized module for handling WebSocket-based communication, which is the primary channel for delivering messages to online clients.
service/config/-Dropwizard uses YAML for configuration. This directory contains samples for the complex setup required to run a Signal instance.

Why This Structure?

Signal Server is a masterclass in 'Focused Engineering'. It avoids bloat and focuses entirely on secure, reliable message routing. Its structure shows how to build a world-class system using a minimalist but robust Java stack.

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