WebSocket in DelphiMVCFramework: Real-Time Communication for Delphi Applications

🚀 An Important Innovation for Delphi Developers

DelphiMVCFramework has recently introduced full support for WebSocket (RFC 6455), both client and server-side. This feature opens new horizons for developing modern applications that require bidirectional real-time communication.

🔌 What is WebSocket and Why It Matters

WebSocket is a standardized communication protocol that enables persistent, full-duplex connections between client and server over a single TCP connection. Unlike traditional HTTP request/response, WebSocket keeps the connection open, allowing both parties to send messages at any time without additional overhead.

The WebSocket protocol (RFC 6455) was designed to work on HTTP/HTTPS ports (80 and 443), overcoming firewall and proxy limitations, making real-time communication accessible in any environment.

A note on Server-Sent Events (SSE): this alternative exists for server-to-client communication, easily implementable and natively supported by browsers. However, SSE is unidirectional (only server → client), while WebSocket offers complete bidirectional communication. If your scenario requires only push notifications from the server, SSE can be a simpler option. But if you need the client to also send messages to the server while maintaining the same connection, WebSocket is the right choice.

💡 Use Cases for Delphi Developers

📊 Real-Time Dashboards and Monitoring Imagine developing a control dashboard for an industrial production system. Until yesterday you would have had to implement a polling mechanism: the client periodically queries the server to check if there’s new data. Each request involves HTTP handshake overhead, headers, TCP connection… and what if the data hasn’t changed? Wasted resources. With WebSocket, the server sends data as soon as it’s available. Your dashboard shows updated KPIs instantly, without delays, without useless polling. The user experience changes radically.

👥 Collaborative Applications Consider a management application where multiple operators work on the same documents. When a user approves an order, others need to know immediately. No manual refresh, no messages like “someone modified the document in the meantime”. With WebSocket, the server notifies all connected clients in real-time: the interface updates automatically, showing the correct state without user intervention.

🏭 IoT and Industry 4.0 In the IoT and Industry 4.0 world, where Delphi continues to be a privileged choice for reliability and performance, WebSocket becomes fundamental. Sensors, PLCs, SCADA systems sending continuous telemetry; VCL or FMX applications monitoring dozens of devices simultaneously, receiving data streams without having to cyclically query each device. Or the opposite case: a desktop application sending control commands to remote machinery, receiving instant execution confirmations.

🌐 Cross-Platform Interoperability And let’s not forget interoperability: WebSocket is a standard protocol (RFC 6455). Your Delphi application can communicate seamlessly with JavaScript clients in the browser, Python services, .NET backends, native mobile apps. You’re not locked into a proprietary ecosystem: you use an open, documented standard, supported everywhere.

💬 Chat and Messaging Think about corporate chat and customer support systems. Applications that until yesterday required complex messaging infrastructures can now be implemented natively in Delphi, both server and client-side. Instant messaging, push notifications, broadcasting to user groups: everything handled with a few lines of code, without external dependencies.

⚡ Simple Yet Powerful Implementation

DMVCFramework provides intuitive APIs for both server and client. The framework automatically handles handshake, HTTP to WebSocket connection upgrade, message framing (text and binary), and ping/pong protocol to keep connections alive. All event handling is thread-safe, so you can update VCL or FMX interfaces without worries.

🔧 Advanced Server Features

The server implementation offers several features that simplify developers’ lives:

⏱️ Automatic Periodic Messages: you can configure the server to send periodic messages to connected clients, without manually managing timers. Just set an interval and define what to send. This feature is perfect for dashboards that need to continuously show updated data: the server “pushes” updates to clients at regular intervals. You can configure different intervals for different clients or dynamically modify the frequency based on specific conditions.

👨‍👩‍👧‍👦 Groups Management: the server natively supports groups (or “rooms”). A client can join one or more groups and receive messages intended only for that group. It’s the perfect pattern for multi-channel chat, team-specific notifications, or selective broadcasting. You can send a message to all clients in a group with a single call, without manually iterating connections.

A practical example? Imagine a management application where each form or view represents a “group”: when a user opens the “Customer Order #12345” form, the client joins the order_12345 group. If they view the “Orders to Process” list, they enter the orders_to_process group. If they check “Today’s Invoice Due Dates”, they join the due_dates_today group. When something changes (an order is processed, an invoice paid, a new due date inserted), the server sends the update only to clients connected to that specific group. Updates become ultra-selective and are sent only to those actually viewing that specific page, list, or document, optimizing bandwidth and resources.

📡 Server Events: the server exposes a series of events covering the entire connection lifecycle:

• OnClientConnect: handle new connections, initialize session data, assign client to groups
• OnClientDisconnect: cleanup resources, notify other clients of disconnection
• OnMessage: receive text messages from clients, process commands, respond
• OnBinaryMessage: handle binary data (streams, files, images)
• OnPeriodicMessage: generate and send custom periodic messages for each client
• OnError: intercept and handle communication errors
• OnLog: monitor server activity for debugging and auditing

📱 Client Events

The WebSocket client offers symmetrical events that make building reactive applications simple:

• OnConnect: notify successful connection, enable user interface, start communication
• OnDisconnect: handle disconnection (voluntary or due to error), update UI, attempt reconnection
• OnTextMessage: receive text messages from server, update displays, show notifications
• OnBinaryMessage: receive binary data, process streams, save files
• OnPong: confirm pong response reception (useful for latency monitoring)
• OnError: handle connection or communication errors

The client also supports configurable 🔄 auto-reconnect: if the connection drops, it can automatically attempt reconnection after a specified interval, making the application more robust in unstable network environments.

The examples included in the repository demonstrate practically all these patterns: multi-room chat, VCL clients with auto-reconnect, servers sending periodic data to JavaScript clients, group management and selective broadcasting.

🎓 Want to Understand How to Best Use WebSocket in Your Applications?

WebSocket support in DMVCFramework is a powerful and versatile feature, but like any technology it requires understanding correct usage patterns, error handling, scalability and implementation best practices.

At ITDevCon 2025 I’ll hold a dedicated session where I’ll delve into:

• 🏗️ Architectural patterns for WebSocket applications
• 💻 Practical implementation of Delphi server and client
• 🚀 Advanced use cases: groups, broadcasting, authentication
• 🔌 Integration with existing applications
• ⚡ Performance and scalability
• 🎯 Real-world use cases and live demos

If you want to bring real-time communication to your Delphi applications and discover how to best leverage this technology, I’ll see you at ITDevCon!

➡️ Register for ITDevCon 2025 and discover all the news from the Delphi world.

📚 Useful Resources

• 🔗 DelphiMVCFramework on GitHub - Official repository with source code and examples
• 📖 Official DelphiMVCFramework Guide - The complete book on Leanpub to master the framework

✨ Conclusion

WebSocket support in DelphiMVCFramework represents an important evolution for modern Delphi application development. The ability to implement bidirectional real-time communication with native APIs, without external dependencies, opens new possibilities for enterprise, IoT, collaborative management applications and much more.

Delphi developers now have a professional tool, based on open standards (RFC 6455), to build the next generation of connected applications. It’s time to bring real-time to your applications! 🚀