engine.io

README

Engine.IO: the realtime engine for golang

Engine.IO is the implementation of transport-based cross-browser/cross-device bi-directional communication layer for Socket.IO for golang.

How to use

Server

(A) Listening on a port

package main

import (
    "os"
    "os/signal"
    "strings"
    "syscall"

    "github.com/zishang520/engine.io/config"
    "github.com/zishang520/engine.io/engine"
    "github.com/zishang520/engine.io/types"
    "github.com/zishang520/engine.io/utils"
)

func main() {
    serverOptions := &config.ServerOptions{}
    serverOptions.SetAllowEIO3(true)
    serverOptions.SetCors(&types.Cors{
        Origin:      "*",
        Credentials: true,
    })

    engineServer := engine.Listen("127.0.0.1:4444", serverOptions, nil)
    engineServer.On("connection", func(sockets ...any) {
        socket := sockets[0].(engine.Socket)
        socket.Send(strings.NewReader("utf 8 string"), nil, nil)
        socket.Send(types.NewBytesBuffer([]byte{0, 1, 2, 3, 4, 5}), nil, nil)
        socket.Send(types.NewBytesBufferString("BufferString by string"), nil, nil)
        socket.Send(types.NewStringBuffer([]byte("StringBuffer by byte")), nil, nil)
        socket.Send(types.NewStringBufferString("StringBuffer by string"), nil, nil)
        socket.On("message", func(...any) {
            // socket.Send(strings.NewReader("utf 8 string"), nil, nil)
        })
    })
    utils.Log().Println("%v", engineServer)

    exit := make(chan struct{})
    SignalC := make(chan os.Signal)

    signal.Notify(SignalC, os.Interrupt, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT)
    go func() {
        for s := range SignalC {
            switch s {
            case os.Interrupt, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT:
                close(exit)
                return
            }
        }
    }()

    <-exit
    os.Exit(0)
}

(B) Intercepting requests for a *types.HttpServer

package main

import (
    "os"
    "os/signal"
    "syscall"

    "github.com/zishang520/engine.io/config"
    "github.com/zishang520/engine.io/engine"
    "github.com/zishang520/engine.io/types"
    "github.com/zishang520/engine.io/utils"
)

func main() {
    serverOptions := &config.ServerOptions{}
    serverOptions.SetAllowEIO3(true)
    serverOptions.SetCors(&types.Cors{
        Origin:      "*",
        Credentials: true,
    })

    http := types.CreateServer(nil).Listen("127.0.0.1:4444", nil)

    engineServer := engine.Attach(http, serverOptions)

    engineServer.On("connection", func(sockets ...any) {
        socket := sockets[0].(engine.Socket)
        socket.On("message", func(...any) {
        })
        socket.On("close", func(...any) {
            utils.Log().Println("client close.")
        })
    })
    utils.Log().Println("%v", engineServer)

    exit := make(chan struct{})
    SignalC := make(chan os.Signal)

    signal.Notify(SignalC, os.Interrupt, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT)
    go func() {
        for s := range SignalC {
            switch s {
            case os.Interrupt, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT:
                close(exit)
                return
            }
        }
    }()

    <-exit
    os.Exit(0)
}

(C) Passing in requests

package main

import (
    "net/http"
    "os"
    "os/signal"
    "syscall"

    "github.com/gorilla/websocket"
    "github.com/zishang520/engine.io/config"
    "github.com/zishang520/engine.io/engine"
    "github.com/zishang520/engine.io/types"
    "github.com/zishang520/engine.io/utils"
)

func main() {
    serverOptions := &config.ServerOptions{}
    serverOptions.SetAllowEIO3(true)
    serverOptions.SetCors(&types.Cors{
        Origin:      "*",
        Credentials: true,
    })

    httpServer := types.CreateServer(nil).Listen("127.0.0.1:4444", nil)

    engineServer := engine.New(serverOptions)

    httpServer.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        if !websocket.IsWebSocketUpgrade(r) {
            engineServer.HandleRequest(types.NewHttpContext(w, r))
        } else if engineServer.Opts().Transports().Has("websocket") {
            engineServer.HandleUpgrade(types.NewHttpContext(w, r))
        } else {
            httpServer.DefaultHandler.ServeHTTP(w, r)
        }
    })

    engineServer.On("connection", func(sockets ...any) {
        socket := sockets[0].(engine.Socket)
        socket.On("message", func(...any) {
        })
        socket.On("close", func(...any) {
            utils.Log().Println("client close.")
        })
    })
    utils.Log().Println("%v", engineServer)

    exit := make(chan struct{})
    SignalC := make(chan os.Signal)

    signal.Notify(SignalC, os.Interrupt, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT)
    go func() {
        for s := range SignalC {
            switch s {
            case os.Interrupt, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT:
                close(exit)
                return
            }
        }
    }()

    <-exit
    httpServer.Close(nil)
    os.Exit(0)
}

(D) Passing in requests (http.Handler interface)

package main

import (
    "net/http"
    "os"
    "os/signal"
    "syscall"

    "github.com/zishang520/engine.io/config"
    "github.com/zishang520/engine.io/engine"
    "github.com/zishang520/engine.io/types"
    "github.com/zishang520/engine.io/utils"
)

func main() {
    serverOptions := &config.ServerOptions{}
    serverOptions.SetAllowEIO3(true)
    serverOptions.SetCors(&types.Cors{
        Origin:      "*",
        Credentials: true,
    })

    engineServer := engine.New(serverOptions)

    engineServer.On("connection", func(sockets ...any) {
        socket := sockets[0].(engine.Socket)
        socket.On("message", func(...any) {
        })
        socket.On("close", func(...any) {
            utils.Log().Println("client close.")
        })
    })

    http.Handle("/engine.io/", engineServer)
    go http.ListenAndServe(":8090", nil)

    utils.Log().Println("%v", engineServer)

    exit := make(chan struct{})
    SignalC := make(chan os.Signal)

    signal.Notify(SignalC, os.Interrupt, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT)
    go func() {
        for s := range SignalC {
            switch s {
            case os.Interrupt, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT:
                close(exit)
                return
            }
        }
    }()

    <-exit

    // Need to handle server shutdown disconnecting client connections.
    engineServer.Close()
    os.Exit(0)
}

Client

<script src="engine.io.js"></script>
<script>
  const socket = new eio.Socket('ws://localhost:4444');
  socket.on('open', () => {
    socket.on('message', data => {});
    socket.on('close', () => {});
  });
</script>

For more information on the client refer to the engine-client repository.

What features does it have?

• Support engine-client 3+

API

Server

---

Top-level

These are exposed by import "github.com/zishang520/engine.io/engine":

Events

• flush
  • Called when a socket buffer is being flushed.
  • Arguments
    • engine.Socket: socket being flushed
    • []*packet.Packet: write buffer
• drain
  • Called when a socket buffer is drained
  • Arguments
    • engine.Socket: socket being flushed

Constants and types

• Protocol (int): protocol revision number
• Server: Server struct
• Socket: Socket struct

Methods

• New

  • Returns a new Server instance. If the first argument is an *types.HttpServer() then the new Server instance will be attached to it. Otherwise, the arguments are passed directly to the Server constructor.
  • Parameters
    • *types.HttpServer: optional, server to attach to.
    • any: optional, options object (see *config.Server#constructor api docs below)

  The following are identical ways to instantiate a server and then attach it.

import "github.com/zishang520/engine.io/config"
import "github.com/zishang520/engine.io/engine"
import "github.com/zishang520/engine.io/types"

var httpServer *types.HttpServer // previously created with `types.CreateServer(nil);`.
var eioServer engine.Server

// create a server first, and then attach
eioServer = engine.NewServer(nil)
eioServer.Attach(httpServer)

// or call the module as a function to get `Server`
eioServer = engine.New(nil)
eioServer.Attach(httpServer)

// immediately attach
eioServer = engine.New(httpServer)

// with custom options
c := &config.ServerOptions{}
c.SetMaxHttpBufferSize(1e3)
eioServer = engine.New(httpServer, c)

• Listen
  • Creates an *types.HttpServer which listens on the given port and attaches WS to it. It returns 501 Not Implemented for regular http requests.
  • Parameters
    • string: address to listen on.
    • any: can be nil, interface config.ServerOptionsInterface or config.AttachOptionsInterface.
    • func(): callback for listen.
  • Options
    • All options from engine.Server.Attach method, documented below.
    • Additionally See Server New below for options you can pass for creating the new Server
  • Returns engine.Server

import "github.com/zishang520/engine.io/engine"
import "github.com/zishang520/engine.io/config"

c := &config.ServerOptions{}
c.SetPingTimeout(2000)
c.SetPingInterval(10000)

const server = engine.Listen("127.0.0.1:3000", c);

server.On('connection', func(...any) {});

• Attach
  • Captures upgrade requests for a *types.HttpServer. In other words, makes a regular *types.HttpServer WebSocket-compatible.
  • Parameters
    • *types.HttpServer: server to attach to.
    • any: config.ServerOptionsInterface: can be nil, interface config.ServerOptionsInterface or config.AttachOptionsInterface
  • Options
    • All options from engine.Server.attach method, documented below.
    • Additionally See Server New below for options you can pass for creating the new Server
  • Returns engine.Server a new Server instance.

engine.Server

The main server/manager. Inherits from events.EventEmitter.

Events

• connection

  • Fired when a new connection is established.
  • Arguments
    • engine.Socket: a Socket object

• initial_headers

  • Fired on the first request of the connection, before writing the response headers
  • Arguments
    • headers (*utils.ParameterBag): a hash of headers
    • ctx (*types.HttpContext): the request

• headers

  • Fired on the all requests of the connection, before writing the response headers
  • Arguments
    • headers (*utils.ParameterBag): a hash of headers
    • ctx (*types.HttpContext): the request

• connection_error

  • Fired when an error occurs when establishing the connection.
  • Arguments
    • types.ErrorMessage: an object with following properties:
      • req (*types.HttpContext): the request that was dropped
      • code (int): one of Server.errors
      • message (string): one of Server.errorMessages
      • context (map[string]any): extra info about the error

Code	Message
-1	"Ok"
0	"Transport unknown"
1	"Session ID unknown"
2	"Bad handshake method"
3	"Bad request"
4	"Forbidden"
5	"Unsupported protocol version"

Read-only methods

Important: if you plan to use Engine.IO in a scalable way, please keep in mind the properties below will only reflect the clients connected to a single process.

• Clients() (*sync.Map): hash of connected clients by id.
• ClientsCount() (uint64): number of connected clients.

Methods

• New
  • Initializes the server
  • Parameters
    • config.ServerOptionsInterface: can be nil, interface config.ServerOptionsInterface
  • Options
    • SetPingTimeout(time.Duration): how many ms without a pong packet to consider the connection closed (20000 * time.Millisecond)
    • SetPingInterval(time.Duration): how many ms before sending a new ping packet (25000 * time.Millisecond)
    • SetUpgradeTimeout(time.Duration): how many ms before an uncompleted transport upgrade is cancelled (10000 * time.Millisecond)
    • SetMaxHttpBufferSize(int64): how many bytes or characters a message can be, before closing the session (to avoid DoS). Default value is 1E6.
    • SetAllowRequest(config.AllowRequest): A function that receives a given handshake or upgrade request as its first argument and can decide whether to continue. error is not empty to indicate that the request was rejected.
    • SetTransports(*types.Set[string]): transports to allow connections to (['polling', 'websocket'])
    • SetAllowUpgrades(bool): whether to allow transport upgrades (true)
    • SetPerMessageDeflate(*types.PerMessageDeflate): parameters of the WebSocket permessage-deflate extension
      • Threshold (int): data is compressed only if the byte size is above this value (1024)
    • SetHttpCompression(*types.HttpCompression): parameters of the http compression for the polling transports
      • Threshold (int): data is compressed only if the byte size is above this value (1024)
    • SetCookie(*http.Cookie): configuration of the cookie that contains the client sid to send as part of handshake response headers. This cookie might be used for sticky-session. Defaults to not sending any cookie (nil).
    • SetCors(*types.Cors): the options that will be forwarded to the cors module. See there for all available options. Defaults to no CORS allowed.
    • SetInitialPacket(io.Reader): an optional packet which will be concatenated to the handshake packet emitted by Engine.IO.
    • SetAllowEIO3(bool): whether to support v3 Engine.IO clients (defaults to false)
• Close
  • Closes all clients
  • Returns engine.Server for chaining
• HandleRequest
  • Called internally when a Engine request is intercepted.
  • Parameters
    • *types.HttpContext: a node request context
• HandleUpgrade
  • Called internally when a Engine ws upgrade is intercepted.
  • Parameters
    • *types.HttpContext: a node request context
• Attach
  • Attach this Server instance to an *types.HttpServer
  • Captures upgrade requests for a *types.HttpServer. In other words, makes a regular *types.HttpServer WebSocket-compatible.
  • Parameters
    • *types.HttpServer: server to attach to.
    • any: can be nil, interface config.AttachOptionsInterface
  • Options
    • SetPath(string): name of the path to capture (/engine.io).
    • SetDestroyUpgrade(bool): destroy unhandled upgrade requests (true)
    • SetDestroyUpgradeTimeout(time.Duration): milliseconds after which unhandled requests are ended (1000 * time.Millisecond)
    • SetAddTrailingSlash(bool): Whether we should add a trailing slash to the request path (true)
• GenerateId
  • Generate a socket id.
  • Overwrite this method to generate your custom socket id.
  • Parameters
    • *types.HttpContext: a node request context
  • Returns A socket id for connected client.

---

engine.Socket

A representation of a client. Inherits from events.EventEmitter.

Events

• close
  • Fired when the client is disconnected.
  • Arguments
    • string: reason for closing
    • any: description (optional)
• message
  • Fired when the client sends a message.
  • Arguments
    • io.Reader: *types.StringBuffer or *types.BytesBuffer with binary contents
• error
  • Fired when an error occurs.
  • Arguments
    • error: error type
• flush
  • Called when the write buffer is being flushed.
  • Arguments
    • []*packet.Packet: write buffer
• drain
  • Called when the write buffer is drained
• packet
  • Called when a socket received a packet (message, ping)
  • Arguments
    • *packet.Packet: packet
• packetCreate
  • Called before a socket sends a packet (message, ping)
  • Arguments
    • *packet.Packet: packet
• heartbeat
  • Called when ping or pong packed is received (depends of client version)

Read-only methods

• Id() (string): unique identifier
• Server() (engine.Server): engine parent reference
• Request() (*types.HttpContext): request that originated the Socket
• Upgraded() (bool): whether the transport has been upgraded
• ReadyState() (string): opening|open|closing|closed
• Transport() (transports.Transport): transport reference

Methods

• Send:
  • Sends a message.
  • Parameters
    • io.Reader: *types.StringBuffer and *strings.Reader are treated as strings, others that implement the io.Reader interface are treated as binary.
    • *packet.Options: can be nil, Options struct.
    • func(transports.Transport): can be nil, a callback executed when the message gets flushed out by the transport
  • *packet.Options
    • Compress (bool): whether to compress sending data. This option might be ignored and forced to be true when using polling. (true)
  • Returns engine.Socket for chaining
• Close
  • Disconnects the client
  • Parameters
    • bool: Flags the transport as discarded. (false)

Client

---

Exposed in the eio global namespace (in the browser), or by require('engine.io-client') (in Node.JS).

For the client API refer to the engine-client repository.

Debug / logging

In order to see all the debug output, run your app with the environment variable DEBUG including the desired scope.

To see the output from all of Engine.IO's debugging scopes you can use:

DEBUG=engine*

Transports

• polling: XHR / JSONP polling transport.
• websocket: WebSocket transport.

Tests

Tests run with make test.

License

MIT License

Copyright (c) 2022 luoyy

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.