PUSH Technologies - An Overview
PUSH Technologies: An Overview
A clear, practical comparison of real-time PUSH technologies used across modern and legacy hybrid systems.
PUSH technologies allow servers to deliver updates to clients instantly when data changes, without requiring repeated polling. This overview covers major PUSH mechanisms—Server-Sent Events, WebSockets, MQTT, Long‑Polling, and Web Push—explaining how each works and where they fit.
WHAT “PUSH” MEANS PUSH reverses the traditional HTTP request/response flow by enabling servers to send updates the moment something meaningful happens. This requires a persistent or semi‑persistent channel, a subscription mechanism, a delivery engine, and triggers that publish events.
SUMMARY COMPARISON SSE: One-way, ideal for notifications and dashboards, low complexity. WebSockets: Full‑duplex, ideal for chat and collaboration, medium–high complexity. MQTT: Pub/Sub, ideal for IoT and distributed systems, medium complexity. Long‑polling: Legacy fallback with high overhead. Web Push: Browser notifications even when inactive.
MAJOR PUSH TECHNOLOGIES
Server‑Sent Events (SSE) Lightweight one-way PUSH over a long-lived HTTP connection with built‑in reconnection. Strengths: Simple, efficient, REST-friendly. Limitations: One-way only; PHP-FPM must be tuned.
WebSockets Full-duplex real-time communication via HTTP Upgrade. Strengths: Low-latency, binary support. Limitations: Requires event-driven server; PHP-FPM unsuitable.
Long-Polling Server holds request until event occurs. Strengths: Universal fallback. Limitations: High request churn; inefficient.
MQTT Lightweight publish/subscribe protocol. Strengths: Scales massively; ideal for IoT and telemetry. Limitations: Requires broker; not native in browsers.
Web Push API Browser push via service workers. Strengths: Works when page is closed. Limitations: Not for continuous streaming.
UNIVERSAL PUSH LIFECYCLE 1. Discovery/Intent 2. Channel Establishment 3. Subscription Registration 4. Delivery
ARCHITECTURE PATTERNS PHP handles authentication, topic negotiation, and event publishing. Push daemon (Perl/Node.js/etc.) handles persistent connections and delivery.
WHEN TO USE WHAT Use SSE when you need simple one-way notifications. Use WebSockets for chat or collaborative apps. Use MQTT for IoT and distributed messaging. Use Long-polling for legacy systems. Use Web Push for browser notifications.
REFERENCES Server-Sent Events — WHATWG WebSockets Protocol — RFC 6455 MQTT v5.0 — OASIS Standard Push API — W3C Recommendation Web Push Protocol — RFC 8030
