refactor old APM [Begin/End]Accept methods on top of Task APIs, and e…

…nable for Unix as well (#51212)

* refactor old APM [Begin/End]Accept methods on top of Task APIs, and enable for Unix as well

* fix BeginAccept to throw synchronously, and relevant test changes

* fix AcceptReceive test to run on unix too

* dispose accepted socket if receive throws

* remove CallbackClosure cache

* fix test helper to indicate AcceptReceive with EAP is still only supported on Windows

Co-authored-by: Geoffrey Kizer <geoffrek@windows.microsoft.com>

src/libraries/System.Net.Sockets/src/System.Net.Sockets.csproj

@@ -43,7 +43,6 @@
  <Compile Include="System\Net\Sockets\TransmitFileOptions.cs" />
  <Compile Include="System\Net\Sockets\UDPClient.cs" />
  <Compile Include="System\Net\Sockets\UdpReceiveResult.cs" />
- <Compile Include="System\Net\Sockets\AcceptOverlappedAsyncResult.cs" />
  <Compile Include="System\Net\Sockets\BaseOverlappedAsyncResult.cs" />
  <Compile Include="System\Net\Sockets\UnixDomainSocketEndPoint.cs" />
  <!-- Logging -->
@@ -89,7 +88,6 @@
  </ItemGroup>
  <ItemGroup Condition="'$(TargetsWindows)' == 'true'">
  <!-- Windows: CoreCLR -->
- <Compile Include="System\Net\Sockets\AcceptOverlappedAsyncResult.Windows.cs" />
  <Compile Include="System\Net\Sockets\BaseOverlappedAsyncResult.Windows.cs" />
  <Compile Include="System\Net\Sockets\DynamicWinsockMethods.cs" />
  <Compile Include="System\Net\Sockets\SafeSocketHandle.Windows.cs" />
@@ -184,7 +182,6 @@
  Link="Common\System\Net\CompletionPortHelper.Windows.cs" />
  </ItemGroup>
  <ItemGroup Condition="'$(TargetsUnix)' == 'true'">
- <Compile Include="System\Net\Sockets\AcceptOverlappedAsyncResult.Unix.cs" />
  <Compile Include="System\Net\Sockets\BaseOverlappedAsyncResult.Unix.cs" />
  <Compile Include="System\Net\Sockets\SafeSocketHandle.Unix.cs" />
  <Compile Include="System\Net\Sockets\Socket.Unix.cs" />

src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Unix.cs

@@ -27,26 +27,6 @@ public SocketInformation DuplicateAndClose(int targetProcessId)
  throw new PlatformNotSupportedException(SR.net_sockets_duplicateandclose_notsupported);
  }
 
- public IAsyncResult BeginAccept(int receiveSize, AsyncCallback? callback, object? state)
- {
- throw new PlatformNotSupportedException(SR.net_sockets_accept_receive_apm_notsupported);
- }
-
- public IAsyncResult BeginAccept(Socket? acceptSocket, int receiveSize, AsyncCallback? callback, object? state)
- {
- throw new PlatformNotSupportedException(SR.net_sockets_accept_receive_apm_notsupported);
- }
-
- public Socket EndAccept(out byte[] buffer, IAsyncResult asyncResult)
- {
- throw new PlatformNotSupportedException(SR.net_sockets_accept_receive_apm_notsupported);
- }
-
- public Socket EndAccept(out byte[] buffer, out int bytesTransferred, IAsyncResult asyncResult)
- {
- throw new PlatformNotSupportedException(SR.net_sockets_accept_receive_apm_notsupported);
- }
-
  internal bool PreferInlineCompletions
  {
  get => _handle.PreferInlineCompletions;

src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Windows.cs

@@ -7,6 +7,7 @@
 using System.IO;
 using System.Runtime.CompilerServices;
 using System.Threading;
+using System.Threading.Tasks;
 using System.Runtime.Versioning;
 
 namespace System.Net.Sockets
@@ -145,30 +146,6 @@ public SocketInformation DuplicateAndClose(int targetProcessId)
  return info;
  }
 
- public IAsyncResult BeginAccept(int receiveSize, AsyncCallback? callback, object? state)
- {
- return BeginAccept(acceptSocket: null, receiveSize, callback, state);
- }
-
- // This is the truly async version that uses AcceptEx.
- public IAsyncResult BeginAccept(Socket? acceptSocket, int receiveSize, AsyncCallback? callback, object? state)
- {
- return BeginAcceptCommon(acceptSocket, receiveSize, callback, state);
- }
-
- public Socket EndAccept(out byte[] buffer, IAsyncResult asyncResult)
- {
- Socket socket = EndAccept(out byte[] innerBuffer, out int bytesTransferred, asyncResult);
- buffer = new byte[bytesTransferred];
- Buffer.BlockCopy(innerBuffer, 0, buffer, 0, bytesTransferred);
- return socket;
- }
-
- public Socket EndAccept(out byte[] buffer, out int bytesTransferred, IAsyncResult asyncResult)
- {
- return EndAcceptCommon(out buffer!, out bytesTransferred, asyncResult);
- }
-
  private DynamicWinsockMethods GetDynamicWinsockMethods()
  {
  return _dynamicWinsockMethods ??= DynamicWinsockMethods.GetMethods(_addressFamily, _socketType, _protocolType);
@@ -439,7 +416,7 @@ private IAsyncResult BeginSendFileInternal(string? fileName, byte[]? preBuffer,
  throw new SocketException((int)errorCode);
  }
 
- asyncResult.FinishPostingAsyncOp(ref Caches.SendClosureCache);
+ asyncResult.FinishPostingAsyncOp();
 
  return asyncResult;
  }