About WebSocket Tester

Test WebSocket connections and frame transmission. Part of the DevTools Surf developer suite. Browse more tools in the API / Config collection.

Use Cases

• Test a real-time chat, notifications, or live data feed endpoint during development.
• Verify server-side message broadcast behavior by connecting multiple simulated clients.
• Test protocol-level behavior: ping/pong keepalives, fragmented messages, and binary frame support.
• Debug latency and throughput for high-frequency WebSocket message streams.

Tips

• Test both the connection lifecycle (connect, send, receive, close) and specific message frames — many WebSocket bugs appear at connection edges, not in steady-state operation.
• Verify that your server sends proper close frames (opcode 0x8) with a status code — clients that receive an abrupt TCP close without a WebSocket close frame may not cleanly reconnect.
• Test with simulated network interruptions — WebSocket connections are persistent and must handle reconnection gracefully. Most clients implement exponential backoff reconnection.

Fun Facts

• The WebSocket protocol was standardized as RFC 6455 in 2011 after two years of development under the IETF HyBi working group. The protocol was controversial because it reused the HTTP upgrade mechanism in a non-standard way.
• WebSocket connections can transfer over 1 Gbps with modern implementations — comparable to raw TCP throughput — making them suitable for real-time applications that would be bottlenecked by HTTP/1.1 polling.
• Socket.IO, one of the most popular WebSocket libraries, defaults to long-polling and upgrades to WebSocket when available — a fallback mechanism designed when WebSocket support was inconsistent across browsers (pre-2012).

FAQ

When should I use WebSockets instead of HTTP long-polling?

Use WebSockets when: you need sub-100ms latency for real-time updates, messages flow in both directions frequently, or you have high message volume that would create excessive HTTP overhead from long-polling. Long-polling is simpler and sufficient for low-frequency server push.

Do WebSockets work through corporate firewalls?

WebSockets use the HTTP Upgrade header and operate on port 80/443, so they pass through most firewalls. However, some aggressive proxy servers intercept and buffer HTTP connections, breaking WebSocket upgrades. WSS (WebSocket Secure, port 443) is most reliably permitted.