simple-websocket-chat

Simple chat example in Go with Gorilla Websocket

This go application shows how to build a simple chat application using websockets.

How to use this application

• Start the application with this command go run ./cmd/main.go
• Open this http://127.0.0.1:8080 in 2 different browsers or tabs
• Use the form to submit username and messages. The messages will be displayed in both tabs thanks to gorilla websockets.

What libraries are used?

• github.com/CloudyKit/jet/v6 for the webpages in go
• net/http is a native network golang lib
• github.com/gorilla/websocket for websocket in go
• Bootstrap for Javascript

How the source code is organised?

• cmd/main.go contains the main application
• html/home.jet contains the webpage with the chat form
• internal folder contains, routing, http handlers, websockets handlers and go routines listening to sockets

How it works?

The application starts and listens

• The app Listen on port 8080 for http request
• A go routine listen on the go channel messagesChan with the line go internal.ListenToMessageChannel()

When an user load a page:

• When the main page has been loaded, a DOM lister document.addEventListener("DOMContentLoaded" ... will make a call to https://127.0.0.1/ws to open a websocket with the go app
• The go application will use a websocket.Upgrader to upgrade the connection from HTTP to WebSocket Protocol. It also starts a go routine to listen to any incoming communication on this websocket: go listenToWs(wscon)

From then, each time that "Enter" is taped in the message field:

• This is captured by the browser in the newMessageField.addEventListener("change", ... and a message with a json payload is send to the go server
• The go routine listening on this websocket receives this payload and send a message for broadcasting it to the go channel messagesChan
• The message is received by the routine ListenToMessageChannel and the message is broadcasted to any existing websockets with conn.WriteJSON(m)
• Each browser/tab receive the message by websocket and catch with the event socket.onmessage = message .. that displays the message in the chat section of the page