Penguji WebSocket

WebSocket is a communication protocol (RFC 6455) that provides full-duplex, bidirectional communication over a single TCP connection. Unlike HTTP, which is request-response (the client requests, the server responds, the connection closes), WebSocket keeps the connection open, allowing the server to push data to the client at any time. This makes WebSocket ideal for real-time applications: chat rooms, live sports updates, collaborative editing, multiplayer games, financial trading dashboards, and IoT device monitoring.

WebSocket connections start with an HTTP handshake -- the client sends an HTTP request with an Upgrade: websocket header, and the server responds with 101 Switching Protocols. After the handshake, the connection switches from HTTP to the WebSocket protocol, and both sides can send messages at any time. Messages can be text (UTF-8 strings, often JSON) or binary (ArrayBuffer/Blob). The WebSocket API in browsers is simple: new WebSocket(url) creates a connection, ws.send(data) sends a message, and ws.onmessage handles incoming messages.

Testing WebSocket connections is essential during development because WebSocket bugs are often timing-related -- messages arrive in the wrong order, connections drop unexpectedly, or reconnection logic fails. A WebSocket tester lets you manually send messages to verify the server's response, test edge cases (empty messages, very large messages, rapid-fire messages), and monitor the server's behavior. Without a tester, you'd need to write custom client code for each test scenario, which is time-consuming and error-prone.

When testing a WebSocket server, start by verifying the connection: does the server accept the connection at the specified URL? Does it require authentication (via headers, query parameters, or a protocol subprotocol)? Test the handshake by checking if the onopen callback fires. Next, test message exchange: send a simple text message and verify the server responds correctly. Test JSON messages by sending a structured payload and checking the response format. Test binary messages by sending an ArrayBuffer and verifying the server handles binary data.

Test error handling by sending malformed messages (incomplete JSON, oversized payloads, invalid UTF-8). Monitor how the server handles connection drops -- close the connection abruptly and see if the server cleans up resources. Test reconnection by closing and reopening the connection. For performance testing, send messages at high frequency (100+ per second) and monitor latency. For load testing, open multiple concurrent connections and check if the server handles them all. Our tool supports all these scenarios with a clean interface for sending messages and viewing the full message history.