websocket

WebSocket client

A self-contained, offline demo of the browser-compatible WebSocket global that host/websocket installs.

main.go starts a localhost echo server (built on the package's server helper), installs the WebSocket global on a VM, and runs main.js. The script uses only the standard WebSocket API to:

• connect (with a subprotocol) and log the open/readyState transition,
• send a text message and a binary message (ArrayBuffer),
• handle the echoed replies via onmessage / addEventListener,
• reconnect automatically after the server abruptly drops the socket (onclose with wasClean === false), using a setTimeout backoff,
• shut down gracefully with ws.close(1000, "bye") on the second session.

go run ./examples/websocket

Expected output:

[client] connecting (attempt 1) to ws://127.0.0.1:PORT/echo
[client] open; protocol="echo" readyState=1
[client] text echo: "hello, server"
[client] binary echo: [103, 111, 106, 115]
[client] asking server to drop the connection...
[client] error: connection closed abnormally
[client] close code=1006 reason="" wasClean=false
[client] reconnecting in 100ms
[client] connecting (attempt 2) to ws://127.0.0.1:PORT/echo
[client] open; protocol="echo" readyState=1
[client] text echo: "hello, server"
[client] binary echo: [103, 111, 106, 115]
[client] done; closing cleanly
[client] close code=1000 reason="bye" wasClean=true
[client] shutdown complete

Notes

• RunString blocks until the event loop drains. An open socket keeps the loop alive (via the interpreter's Pin mechanism), and setTimeout keeps it alive during the reconnect backoff, so the program exits only after the final clean close.
• gojs has no Blob, so binary frames always arrive as an ArrayBuffer. The script reads bytes with a DataView because gojs has no Uint8Array sugar yet.