【发布时间】：2010-04-03 17:18:42
【问题描述】：
使用 F# 中的原始套接字编写异步 Ping，以使用尽可能少的线程启用并行请求。不使用“System.Net.NetworkInformation.Ping”，因为它似乎为每个请求分配一个线程。我也对使用 F# 异步工作流感兴趣。
当目标主机不存在/响应时，下面的同步版本正确超时，但异步版本挂起。当主机响应时，两者都起作用。不确定这是 .NET 问题还是 F# 问题...
有什么想法吗？
（注意：该进程必须以管理员身份运行才能允许原始套接字访问）
这会引发超时：
let result = Ping.Ping ( IPAddress.Parse( "192.168.33.22" ), 1000 )
但是，这会挂起：
let result = Ping.AsyncPing ( IPAddress.Parse( "192.168.33.22" ), 1000 )
|> Async.RunSynchronously
这是代码...
module Ping
open System
open System.Net
open System.Net.Sockets
open System.Threading
//---- ICMP Packet Classes
type IcmpMessage (t : byte) =
let mutable m_type = t
let mutable m_code = 0uy
let mutable m_checksum = 0us
member this.Type
with get() = m_type
member this.Code
with get() = m_code
member this.Checksum = m_checksum
abstract Bytes : byte array
default this.Bytes
with get() =
[|
m_type
m_code
byte(m_checksum)
byte(m_checksum >>> 8)
|]
member this.GetChecksum() =
let mutable sum = 0ul
let bytes = this.Bytes
let mutable i = 0
// Sum up uint16s
while i < bytes.Length - 1 do
sum <- sum + uint32(BitConverter.ToUInt16( bytes, i ))
i <- i + 2
// Add in last byte, if an odd size buffer
if i <> bytes.Length then
sum <- sum + uint32(bytes.[i])
// Shuffle the bits
sum <- (sum >>> 16) + (sum &&& 0xFFFFul)
sum <- sum + (sum >>> 16)
sum <- ~~~sum
uint16(sum)
member this.UpdateChecksum() =
m_checksum <- this.GetChecksum()
type InformationMessage (t : byte) =
inherit IcmpMessage(t)
let mutable m_identifier = 0us
let mutable m_sequenceNumber = 0us
member this.Identifier = m_identifier
member this.SequenceNumber = m_sequenceNumber
override this.Bytes
with get() =
Array.append (base.Bytes)
[|
byte(m_identifier)
byte(m_identifier >>> 8)
byte(m_sequenceNumber)
byte(m_sequenceNumber >>> 8)
|]
type EchoMessage() =
inherit InformationMessage( 8uy )
let mutable m_data = Array.create 32 32uy
do base.UpdateChecksum()
member this.Data
with get() = m_data
and set(d) = m_data <- d
this.UpdateChecksum()
override this.Bytes
with get() =
Array.append (base.Bytes)
(this.Data)
//---- Synchronous Ping
let Ping (host : IPAddress, timeout : int ) =
let mutable ep = new IPEndPoint( host, 0 )
let socket = new Socket( AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp )
socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.SendTimeout, timeout )
socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, timeout )
let packet = EchoMessage()
let mutable buffer = packet.Bytes
try
if socket.SendTo( buffer, ep ) <= 0 then
raise (SocketException())
buffer <- Array.create (buffer.Length + 20) 0uy
let mutable epr = ep :> EndPoint
if socket.ReceiveFrom( buffer, &epr ) <= 0 then
raise (SocketException())
finally
socket.Close()
buffer
//---- Entensions to the F# Async class to allow up to 5 paramters (not just 3)
type Async with
static member FromBeginEnd(arg1,arg2,arg3,arg4,beginAction,endAction,?cancelAction): Async<'T> =
Async.FromBeginEnd((fun (iar,state) -> beginAction(arg1,arg2,arg3,arg4,iar,state)), endAction, ?cancelAction=cancelAction)
static member FromBeginEnd(arg1,arg2,arg3,arg4,arg5,beginAction,endAction,?cancelAction): Async<'T> =
Async.FromBeginEnd((fun (iar,state) -> beginAction(arg1,arg2,arg3,arg4,arg5,iar,state)), endAction, ?cancelAction=cancelAction)
//---- Extensions to the Socket class to provide async SendTo and ReceiveFrom
type System.Net.Sockets.Socket with
member this.AsyncSendTo( buffer, offset, size, socketFlags, remoteEP ) =
Async.FromBeginEnd( buffer, offset, size, socketFlags, remoteEP,
this.BeginSendTo,
this.EndSendTo )
member this.AsyncReceiveFrom( buffer, offset, size, socketFlags, remoteEP ) =
Async.FromBeginEnd( buffer, offset, size, socketFlags, remoteEP,
this.BeginReceiveFrom,
(fun asyncResult -> this.EndReceiveFrom(asyncResult, remoteEP) ) )
//---- Asynchronous Ping
let AsyncPing (host : IPAddress, timeout : int ) =
async {
let ep = IPEndPoint( host, 0 )
use socket = new Socket( AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp )
socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.SendTimeout, timeout )
socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, timeout )
let packet = EchoMessage()
let outbuffer = packet.Bytes
try
let! result = socket.AsyncSendTo( outbuffer, 0, outbuffer.Length, SocketFlags.None, ep )
if result <= 0 then
raise (SocketException())
let epr = ref (ep :> EndPoint)
let inbuffer = Array.create (outbuffer.Length + 256) 0uy
let! result = socket.AsyncReceiveFrom( inbuffer, 0, inbuffer.Length, SocketFlags.None, epr )
if result <= 0 then
raise (SocketException())
return inbuffer
finally
socket.Close()
}
【问题讨论】：
-
您有什么特别的理由要重新发明 System.Net.NetworkInformation.Ping.SendAsync()？它已经支持超时。
-
SendAsync/SendToAsync 和上面的 AsyncSendTo 不一样……前者不与 F# 异步工作流集成（大大简化了异步代码的编写）。
-
呃，重点是不用写。
-
抱歉，没有阅读完整的回复...重新发明的两个原因。首先，文档暗示 Ping.SendAsync 每个实例使用一个线程，这限制了它的可伸缩性，而 Begin/End 没有。其次，我想了解如何操作原始套接字以用于其他非 TCP/UDP 协议。
-
@nobugz - 对此进行了测试，并且 System.Net.NetworkInformation.Ping.SendAsync 无法扩展。尝试快速扫描 B 类会消耗 100 多个线程，最终会耗尽内存。使用 Begin/End（通过 F# 异步工作流）只需要几个线程和几百 Mb。
标签： .net sockets f# asynchronous raw-sockets