Missing Socket APIs mega-issue

We still have a few gaps in our Socket APIs where we are missing support for Task, Span/Memory, or CancellationToken.

This is a mega-issue to track all remaining work here for 6.0.

Async Socket APIs:

• AcceptAsync needs CancellationToken support -- implemented in https://github.com/dotnet/runtime/pull/53340

	public static ValueTask<Socket> AcceptAsync (this Socket socket, CancellationToken cancellationToken);
	public static ValueTask<Socket> AcceptAsync (this Socket socket, Socket acceptSocket, CancellationToken cancellationToken);

• SendToAsync, ReceiveFromAsync, and ReceiveMessageFromAsync need Memory and CancellationToken support -- see #33418. (Note, this should probably wait until #41502 is completed.)

	public static ValueTask<int> SendToAsync(this Socket socket, ReadOnlyMemory<byte> buffer, SocketFlags socketFlags, EndPoint remoteEP, CancellationToken cancellationToken = null);
	public static ValueTask<SocketReceiveFromResult> ReceiveFromAsync(this Socket socket, Memory<byte> buffer, SocketFlags socketFlags, EndPoint remoteEP, CancellationToken cancellationToken = null);
	public static ValueTask<SocketReceiveMessageFromResult> ReceiveMessageFromAsync(this Socket socket, Memory<byte> buffer, SocketFlags socketFlags, EndPoint remoteEP, CancellationToken cancellationToken = null);

• Add Task-based SendFileAsync with Memory and CancellationToken support -- implemented in https://github.com/dotnet/runtime/pull/52208 and https://github.com/dotnet/runtime/pull/53062

        public ValueTask SendFileAsync(string? fileName, CancellationToken cancellationToken = default);
        public ValueTask SendFileAsync(string? fileName, ReadOnlyMemory<byte> preBuffer, ReadOnlyMemory<byte> postBuffer, TransmitFileOptions flags, CancellationToken cancellationToken = default);

• Add Task-based DisconnectAsync -- implemented in https://github.com/dotnet/runtime/pull/51213

        public static ValueTask DisconnectAsync(this Socket socket, bool reuseSocket, CancellationToken cancellationToken=default);

Sync Socket APIs:

• SendTo, ReceiveFrom, ReceiveMessageFrom need Span support -- implemented in https://github.com/dotnet/runtime/pull/51956 and https://github.com/dotnet/runtime/pull/46285

	public int SendTo(ReadOnlySpan<byte> buffer, EndPoint remoteEP);
	public int SendTo(ReadOnlySpan<byte> buffer, SocketFlags socketFlags, EndPoint remoteEP);
	public int ReceiveFrom(Span<byte> buffer, ref EndPoint remoteEP);
	public int ReceiveFrom(Span<byte> buffer, SocketFlags socketFlags, ref EndPoint remoteEP);
        public int ReceiveMessageFrom(Span<byte> buffer, ref System.Net.Sockets.SocketFlags socketFlags, ref System.Net.EndPoint remoteEP, out System.Net.Sockets.IPPacketInformation ipPacketInformation);

• SendFile needs Span support -- implemented in https://github.com/dotnet/runtime/pull/47230

        public void SendFile(string fileName, ReadOnlySpan<byte> preBuffer, ReadOnlySpan<byte> postBuffer, TransmitFileOptions flags);

Async TcpListener APIs:

• Accept async methods need CancellationToken support -- implemented in https://github.com/dotnet/runtime/pull/53340

	public ValueTask<Socket> AcceptSocketAsync (CancellationToken cancellationToken);
	public ValueTask<TcpClient> AcceptTcpClientAsync (CancellationToken cancellationToken);

Async TcpClient APIs:

• Add missing ConnectAsync overloads -- implemented in https://github.com/dotnet/runtime/pull/44110

namespace System.Net.Sockets
{
    public class TcpClient : IDisposable
    {
        public Task ConnectAsync(IPEndPoint remoteEP);
        public ValueTask ConnectAsync(IPEndPoint remoteEP, CancellationToken cancellationToken);
    }
}

UdpClient APIs:

• UdpClient Span, Memory, and CancellationToken support -- see https://github.com/dotnet/runtime/issues/864

public class UdpClient
{
    public int Send(ReadOnlySpan<byte> datagram);
    public int Send(ReadOnlySpan<byte> datagram, IPEndPoint endPoint);
    public int Send(ReadOnlySpan<byte> datagram, string hostname, int port);
    public ValueTask<int> SendAsync(ReadOnlyMemory<byte> datagram, CancellationToken cancellationToken);
    public ValueTask<int> SendAsync(ReadOnlyMemory<byte> datagram, IPEndPoint endPoint, CancellationToken cancellationToken);
    public ValueTask<UdpReceiveResult> ReceiveAsync(CancellationToken cancellationToken);
}

Related issues

• Move Task-based methods from SocketTaskExtensions to Socket -- see #43901
• Memory support for SendPacketElements -- see #45267
• Consider overloads for Task-based methods that remove #SocketFlags argument -- see #43934
• Remove Socket finalizer and ensure SafeSocketHandle finalization works correctly -- see #43383
• New APIs for zero-allocation connectionless sockets -- see #30797