如何在温文尔雅中实现服务器推送websocket？

Question

我能写这样的东西吗？

let echo (ws: WebSocket) =
    fun ctx -> socket {
        let loop = ref true            
        while !loop do
            let! message = Async.Choose (ws.read()) (inbox.Receive())
            match message with
            | Choice1Of2 (wsMessage) ->
                match wsMessage with
                | Ping, _, _ -> do! ws.send Pong [||] true
                | _ -> ()
            | Choice2Of2 pushMessage -> do! ws.send Text pushMessage true
    }

或者我需要2个单独的套接字循环来进行并发读写？

Answer 1

我认为你可以解决这个问题Async.Choose(有很多实现 - 虽然我不确定哪个是最规范的).

也就是说,您当然可以创建两个循环 - 内部读取一个循环,socket { .. }以便您可以从Web套接字接收数据; 写作可以是普通的async { ... }块.

像这样的东西应该做的伎俩:

let echo (ws: WebSocket) =  
    // Loop that waits for the agent and writes to web socket
    let notifyLoop = async { 
      while true do 
        let! msg = inbox.Receive()
        do! ws.send Text msg }

    // Start this using cancellation token, so that you can stop it later
    let cts = new CancellationTokenSource()
    Async.Start(notifyLoop, cts.Token)

    // The loop that reads data from the web socket
    fun ctx -> socket {
        let loop = ref true            
        while !loop do
            let! message = ws.read()
            match message with
            | Ping, _, _ -> do! ws.send Pong [||] true
            | _ -> () }

Answer 2

Async.Choose 没有正确的实现（至少对于这种情况），因此我们需要两个异步循环来进行并发读写；有关更多详细信息，请参阅此