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package sse

import "go.fuchsia.dev/fuchsia/garnet/go/src/sse"

Copyright 2018 The Fuchsia Authors. All rights reserved. Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.

Package sse provides support for Server-Sent Events, as a handler for net/http, and a client that can read SSE events from net/http responses.

SSE is specified here: http://www.w3.org/TR/eventsource/

The package implements only partial support for SSE, specifically the client and server do not handle retries or event buffering.



Package Files

client.go event.go sse.go


var ErrNotAcceptable = errors.New("sse: invalid content-type")

ErrNotAcceptable occurs when the incoming request does not Accept text/event-stream

func Start Uses

func Start(w http.ResponseWriter, r *http.Request) error

Start asserts that the client wants SSE, and if so, begins writing an SSE stream with the appropriate response headers. It performs a forced flush on the stream to ensure that the client receives the headers immediately.


http.HandleFunc("/example/startsse", func(w http.ResponseWriter, r *http.Request) {
    err := Start(w, r)
    if err != nil {
    ticker := time.NewTicker(time.Second)
    for {
        select {
        case <-ticker.C:
            helloWorld := &Event{Data: []byte("hello world")}
        case <-r.Context().Done():

func Write Uses

func Write(w http.ResponseWriter, e *Event) error

Write sends an event to an http ResponseWriter, flushing afterward.

type Client Uses

type Client struct {
    // contains filtered or unexported fields

Client provides a handle to methods that are bound to a single SSE stream.

func New Uses

func New(r *http.Response) (*Client, error)

New constructs a new SSE client against the http.Response. It returns an error if the response is not a valid SSE response, for example carrying the incorrect content type, or not having a response body stream. In cases where the error is an SSE protocol issue, ProtocolError is returned.

func (*Client) ReadEvent Uses

func (c *Client) ReadEvent() (*Event, error)

ReadEvent parses the next event out of the response body, blocking if none is yet available. It returns either an Event or an error. error is either a ProtocolError or one of various IO errors, such as io.EOF.

type Event Uses

type Event struct {
    Event string
    Data  []byte
    ID    string
    Retry *int

Event represents a single Server-Sent Event.

func (*Event) Marshal Uses

func (e *Event) Marshal() []byte

Marshal returns a string in the SSE wire format, with the Data field repeated for an ocurrences of line breaks in the bytes.

func (*Event) String Uses

func (e *Event) String() string

String returns the same format as Marshal

func (*Event) WriteTo Uses

func (e *Event) WriteTo(w io.Writer) (int64, error)

WriteTo marshals the event and writes it to the given stream. HTTP users will likely prefer to use sse.Write instead, as that handles flushing the stream.

type ProtocolError Uses

type ProtocolError struct {
    Response *http.Response
    Err      error

ProtocolError provides details of any protocol error that has occurred, the original Response object and an Error that contains a description of the problem.

func (*ProtocolError) Error Uses

func (pe *ProtocolError) Error() string

Package sse imports 8 packages (graph). Updated 2020-05-21. Refresh now. Tools for package owners.