[API Proposal]: ValueTask-based Socket.ConnectAsync overloads for Happy Eyeballs #117548

namespace System.Net.Sockets;

public class Socket
{
    // Existing:
    public ValueTask ConnectAsync(EndPoint remoteEP, CancellationToken cancellationToken);
    public static bool ConnectAsync(SocketType socketType, ProtocolType protocolType, SocketAsyncEventArgs e)

    // Approved in #861 / #87932
    public static bool ConnectAsync(SocketType socketType, ProtocolType protocolType, SocketAsyncEventArgs e, ConnectAlgorithm connectAlgorithm);

    // Proposed:
    public ValueTask ConnectAsync(DnsEndPoint remoteEP, ConnectAlgorithm connectAlgorithm, CancellationToken cancellationToken = default);

    // Also consider (needs more implementation work)
    public ValueTask ConnectAsync(IPAddress[] addresses, int port, ConnectAlgorithm connectAlgorithm, CancellationToken cancellationToken)
}

public async ValueTask<Stream> ConnectToTcpHostAsync(string host, int port, CancellationToken cancellationToken)
{
    try
    {
        Socket socket = new Socket(SocketType.Stream, ProtocolType.Tcp) { NoDelay = true };
        await socket.ConnectAsync(endPoint, ConnectAlgorithm.Parallel, cancellationToken).ConfigureAwait(false);
        return new NetworkStream(socket, ownsSocket: true);
    }
    catch
    {
        socket.Dispose();
        throw;
    }
}

using SocketsHttpHandler handler = new SocketsHttpHandler();
handler.ConnectCallback = async (ctx, ct) =>
{
    DnsEndPoint dnsEndPoint = ctx.DnsEndPoint;
    IPAddress[] addresses = await Dns.GetHostAddressesAsync(dnsEndPoint.Host, dnsEndPoint.AddressFamily, ct);

    LogResolvedAdresses(addresses);

    var s = new Socket(SocketType.Stream, ProtocolType.Tcp) { NoDelay = true };
    try
    {
        await s.ConnectAsync(addresses, dnsEndPoint.Port, ConnectAlgorithm.Parallel, ct);
        return new NetworkStream(s, ownsSocket: true);
    }
    catch
    {
        s.Dispose();
        throw;
    }
};