sse

README

Server-Sent Events (EventSource)

A self-contained, offline demo of the host/sse package. main.go starts a localhost text/event-stream server, builds a VM with print + time + timer providers and sse.Install, and runs main.js.

go run ./examples/sse

The server pushes an id:'d message and a named tick event every 300ms. It drops the first connection after two messages to force an automatic reconnect; the client reconnects with a Last-Event-ID header, and the server resumes the id sequence from there. After ~2.5s the script calls es.close() and the process exits.

main.js demonstrates:

• onopen and onmessage handler properties,
• a named-event listener via addEventListener("tick", …),
• onerror firing on the reconnect (with readyState back to CONNECTING),
• Last-Event-ID continuity, visible as a monotonically increasing e.lastEventId,
• close() ending the stream so RunString returns.

Example output (ports and exact interleaving vary):

SSE server listening at http://127.0.0.1:PORT
connecting to http://127.0.0.1:PORT
[open] readyState = 1 (OPEN = 1)
[message] message #1 | lastEventId = 1 | origin = http://127.0.0.1:PORT
[tick] value = 1
server: dropping first connection to force a reconnect
[message] message #2 | lastEventId = 2 | origin = http://127.0.0.1:PORT
[tick] value = 2
[error] readyState = 0 -> reconnecting
server: client reconnected with Last-Event-ID="2"
[open] readyState = 1 (OPEN = 1)
[message] message #3 | lastEventId = 3 | origin = http://127.0.0.1:PORT
[tick] value = 3
...
closing EventSource
[closed] readyState = 2 (CLOSED = 2)
done

Documentation

Overview

Example: Server-Sent Events (EventSource) in gojs.

This program is fully self-contained and runs OFFLINE. It starts a localhost SSE server that pushes a periodic "message" event, a custom "tick" event, and an ever-increasing id:, then deliberately drops the connection once so the client demonstrates automatic reconnection with Last-Event-ID. A gojs VM with a print provider, a timer provider, and the sse host package loads main.js, which wires up onopen/onmessage, a named-event listener, and onerror, and closes the stream after a few seconds so the process exits cleanly.