webobs

README

About

Web observer is a go library that creates websocket handlers at runtime for communicating between your go program and web browsers that support websockets. You could use it for monitoring or stats building. I created this package so that I could debug and visualize results from my Go program on a browser with the ease of javascript/css/...

Installation

go get github.com/mlo77/webobs

Usage

In your Go program,

	// creates a http server on 8080 
	wobs := webobs.StartServer(":8080")

	// set a channel ready to be connected
	// from the address http://localhost:8080/fooTag
    wobs.SetChannel("fooTag", browserToThisAppCallback, "./pathToHtmlResources")

Open a browser and open http://localhost:8080/fooTag The Go web server will serve /pathToHtmlResources/fooTag.html if it exists, otherwise it will generate a template that you can build up from.

The javascript side code typically looks like this

    var soc = new WebSocket("ws://"+window.location.host+"/"+{{.Tagws}})

    // receive data from Go app
    soc.onmessage = function (event) {
    	var obj = JSON.parse(event.data)
    	console.log(obj)
    }

    // send data to Go app
    soc.send(JSON.stringify({ foo:1, bar:0 }))

As soon as the browser hits the address, a websocket connection is setup allowing to pass data between Go and the browser.

Back to your Go program

	func browserToThisAppCallback(tag string, data []byte) {
	    var obj SomeStruct
	    err := json.Unmarshal(data, &obj)
	    if err != nil {
	        fmt.Println("error:", err)
	    }
	    ....
	}

	// Sends data to all browser connected to http://localhost:8080/fooTag
	wobs.WriteCh <- webobs.Message{ Tag: "fooTag", Data: []byte("hello") }

	// If there is no websocket connected the above line does nothing

Licence

MIT Licence

Documentation

Overview

Package webobs provides creation of websocket handlers at runtime, allowing easy communication between go program and web browsers

Index

• type Listener
• type Message
• type Server
  • func StartServer(port string) *Server
  • func (s *Server) HasRegisteredClient(tag string) bool
  • func (s *Server) SetChannel(tag string, l Listener, path string)
  • func (s *Server) ShutClientsForTag(tag string)

Types

type Listener

type Listener func(tag string, data []byte)

Listener is the callback type when receiving messages from web observers

type Message

type Message struct {
	// Tag categories the message
	Tag string
	// Data contains data, may be marshalled to JSON
	Data []byte
}

type Server

type Server struct {

	// WriteCh is used whenever the application wish to send messages
	// the web observers (websocket connected browsers)
	WriteCh chan Message
	// contains filtered or unexported fields
}

func StartServer

func StartServer(port string) *Server

StartServer creates and starts a http server with no handles, it awaits for channels to be set.

func (*Server) HasRegisteredClient

func (s *Server) HasRegisteredClient(tag string) bool

HasRegisteredClient returns whether there is a client for given tag

func (*Server) SetChannel

func (s *Server) SetChannel(tag string, l Listener, path string)

SetChannel adds a websocket handle and http handle to serve rendered html pages and scripts

func (*Server) ShutClientsForTag

func (s *Server) ShutClientsForTag(tag string)

Shut all clients connected to a specific tag