WebSockets.jl

This is a server-side implementation of the WebSockets protocol in Julia. If you want to write a web app in Julia that uses WebSockets, you'll need this package.

This package works with HttpServer.jl, which is what you use to set up a server that accepts HTTP(S) connections.

As a first example, we can create a WebSockets echo server:

using HttpServer
using WebSockets

wsh = WebSocketHandler() do req,client
    while true
        msg = read(client)
        write(client, msg)
    end
  end

server = Server(wsh)
run(server,8080)

This sets up a server running on localhost, port 8080. It will accept WebSockets connections. The function in wsh will be called once per connection; it takes over that connection. In this case, it reads each msg from the client and then writes the same message back: a basic echo server.

The function that you pass to the WebSocketHandler constructor takes two arguments: a Request from HttpCommon.jl, and a WebSocket from here.

What can you do with a WebSocket?

You can:

• write data to it
• read data from it
• send ping or pong messages
• close the connection

Installation/Setup

julia> Pkg.add("WebSockets")

At this point, you can use the examples below to test that it all works.

Chat client/server example:

1. Move to the ~/.julia/<version>/WebSockets directory
2. Run julia examples/chat.jl
3. In a web browser, open localhost:8000
4. You should see a basic IRC-like chat application

Echo server example:

using HttpServer
using WebSockets

wsh = WebSocketHandler() do req,client
    while true
        msg = read(client)
        write(client, msg)
    end
  end

server = Server(wsh)
run(server,8080)

To play with a WebSockets echo server, you can:

1. Paste the above code in to the Julia REPL
2. Open localhost:8080 in Chrome
3. Open the Chrome developers tools console
4. Type ws = new WebSocket("ws://localhost:8080"); into the console
5. Type ws.send("hi") into the console.
6. Switch to the 'Network' tab; click on the request; click on the 'frames' tab.
7. You will see the two frames containing "hi": one sent and one received.

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