Async.FromBeginEnd<'T> Method (F#)
Creates an asynchronous computation in terms of a Begin/End pair of actions in the style used in CLI APIs.
Namespace/Module Path: Microsoft.FSharp.Control
Assembly: FSharp.Core (in FSharp.Core.dll)
// Signature:
static member FromBeginEnd : (AsyncCallback * obj -> IAsyncResult) * (IAsyncResult -> 'T) * ?(unit -> unit) -> Async<'T>
// Usage:
Async.FromBeginEnd (beginAction, endAction)
Async.FromBeginEnd (beginAction, endAction, cancelAction = cancelAction)
Parameters
beginAction
Type: AsyncCallback * obj -> IAsyncResultThe function initiating a traditional CLI asynchronous operation.
endAction
Type: IAsyncResult -> 'TThe function completing a traditional CLI asynchronous operation.
cancelAction
Type: (unit -> unit)An optional function to be executed when a cancellation is requested.
Return Value
An asynchronous computation wrapping the given Begin/End functions.
Remarks
For example, the following code creates an asynchronous computation that wraps a web service call.
Async.FromBeginEnd(ws.BeginGetWeather,ws.EndGetWeather)
When the computation is run, beginFunc is executed, with a callback which represents the continuation of the computation. When the callback is invoked, the overall result is fetched using endFunc.
The computation will respond to cancellation while waiting for the completion of the operation. If a cancellation occurs, and cancelAction is specified, then it is executed, and the computation continues to wait for the completion of the operation. If cancelAction is not specified, cancellation causes the computation to stop immediately, and subsequent invocations of the callback are ignored.
Example
The following code example shows how to create an F# asynchronous computation from a .NET asynchronous API that uses the Begin/End pattern. The example uses the .NET socket API in System.Net.Sockets. It is an implementation of a simple server application that accepts a connection, receives data from a client, and sends a response.
module SocketServer =
open System.Net
open System.Net.Sockets
open System.Collections.Generic
let toIList<'T> (data : 'T array) =
let segment = new System.ArraySegment<'T>(data)
let data = new List<System.ArraySegment<'T>>() :> IList<System.ArraySegment<'T>>
data.Add(segment)
data
type Socket with
member this.MyAcceptAsync() =
Async.FromBeginEnd((fun (callback, state) -> this.BeginAccept(callback, state)),
this.EndAccept)
member this.MyConnectAsync(ipAddress : IPAddress, port : int) =
Async.FromBeginEnd(ipAddress, port,
(fun (ipAddress:IPAddress, port, callback, state) ->
this.BeginConnect(ipAddress, port, callback, state)),
this.EndConnect)
member this.MySendAsync(data : byte array, flags : SocketFlags) =
Async.FromBeginEnd(toIList data, flags,
(fun (data : IList<System.ArraySegment<byte>>,
flags : SocketFlags, callback, state) ->
this.BeginSend(data, flags, callback, state)),
this.EndSend)
member this.MyReceiveAsync(data : byte array, flags : SocketFlags) =
Async.FromBeginEnd(toIList data, flags,
(fun (data : IList<System.ArraySegment<byte>>,
flags : SocketFlags, callback, state) ->
this.BeginReceive(data, flags, callback, state)),
this.EndReceive)
let port = 11000
let socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
let ipHostInfo = Dns.Resolve(Dns.GetHostName())
let localIPAddress = ipHostInfo.AddressList.[0]
let localEndPoint = new IPEndPoint(localIPAddress, port)
socket.Bind(localEndPoint)
let connectSendReceive (socket : Socket) =
async {
do! socket.MyConnectAsync(ipHostInfo.AddressList.[0], 11000)
let buffer1 = [| 0uy .. 255uy |]
let buffer2 = Array.zeroCreate<byte> 255
let flags = new SocketFlags()
let! flag = socket.MySendAsync(buffer1, flags)
let! result = socket.MyReceiveAsync(buffer2, flags)
return buffer2
}
let acceptReceiveSend (socket : Socket) =
async {
printfn "Listening..."
socket.Listen(10)
printfn "Accepting..."
let! socket = socket.MyAcceptAsync()
let buffer1 = Array.zeroCreate<byte> 256
let flags = new SocketFlags()
printfn "Receiving..."
let! nBytes = socket.MyReceiveAsync(buffer1, flags)
printfn "Received %d bytes from client computer." nBytes
let buffer2 = Array.rev buffer1
printfn "Sending..."
let! flag = socket.MySendAsync(buffer2, flags)
printfn "Completed."
return buffer2
}
let taskServer = Async.StartAsTask(acceptReceiveSend(socket))
taskServer.Wait()
socket.Close()
Listening... Accepting... Receiving... Received 256 bytes from client computer. Sending... Completed.
The following code example shows the client code that can be used together with the server code in the previous example.
module SocketClient =
open System.Net
open System.Net.Sockets
open System.Collections.Generic
let toIList<'T> (data : 'T array) =
let segment = new System.ArraySegment<'T>(data)
let data = new List<System.ArraySegment<'T>>() :> IList<System.ArraySegment<'T>>
data.Add(segment)
data
type Socket with
member this.MyAcceptAsync(receiveSize) =
Async.FromBeginEnd(receiveSize,
(fun (receiveSize, callback, state) ->
this.BeginAccept(receiveSize, callback, state)),
this.EndConnect)
member this.MyConnectAsync(ipAddress : IPAddress, port : int) =
Async.FromBeginEnd(ipAddress, port,
(fun (ipAddress:IPAddress, port, callback, state) ->
this.BeginConnect(ipAddress, port, callback, state)),
this.EndConnect)
member this.MySendAsync(data, flags : SocketFlags) =
Async.FromBeginEnd(toIList data, flags,
(fun (data : IList<System.ArraySegment<byte>>,
flags : SocketFlags, callback, state) ->
this.BeginSend(data, flags, callback, state)),
this.EndSend)
member this.MyReceiveAsync(data, flags : SocketFlags) =
Async.FromBeginEnd(toIList data, flags,
(fun (data : IList<System.ArraySegment<byte>>,
flags : SocketFlags, callback, state) ->
this.BeginReceive(data, flags, callback, state)),
this.EndReceive)
let port = 11000
let socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
let ipHostEntry = Dns.Resolve("hostname.contoso.com")
printfn "Server address: %s" (ipHostEntry.AddressList.[0].ToString())
let connectSendReceive (socket : Socket) =
async {
do! socket.MyConnectAsync(ipHostEntry.AddressList.[0], 11000)
printfn "Connected to remote host."
let buffer1 = [| 0uy .. 255uy |]
let buffer2 = Array.zeroCreate<byte> 255
let flags = new SocketFlags()
printfn "Sending data..."
let! flag = socket.MySendAsync(buffer1, flags)
printfn "Receiving data..."
let! result = socket.MyReceiveAsync(buffer2, flags)
printfn "Received data from remote host."
return buffer2
}
let acceptReceiveSend (socket : Socket) =
async {
socket.Listen(1)
do! socket.MyAcceptAsync(256)
let buffer1 = Array.zeroCreate<byte> 255
let flags = new SocketFlags()
let! flag = socket.MyReceiveAsync(buffer1, flags)
let buffer2 = Array.rev buffer1
let! flag = socket.MySendAsync(buffer2, flags)
return buffer2
}
let taskClient = Async.StartAsTask(connectSendReceive(socket))
taskClient.Wait()
taskClient.Result |> Array.iter (fun elem -> printf "%d " elem)
Sample Output
Server address: 10.80.57.8 Connected to remote host. Sending data... Receiving data... Received data from remote host. 255 254 253 252 251 250 249 248 247 246 ...
Platforms
Windows 7, Windows Vista SP2, Windows XP SP3, Windows XP x64 SP2, Windows Server 2008 R2, Windows Server 2008 SP2, Windows Server 2003 SP2
Version Information
F# Runtime
Supported in: 2.0, 4.0
Silverlight
Supported in: 3