SocketsHttpHandler.ConnectCallback Property

Definition

Namespace:

System.Net.Http

Assembly:

System.Net.Http.dll

Source:

SocketsHttpHandler.cs

Gets or sets a custom callback used to open new connections.

C#

public Func<System.Net.Http.SocketsHttpConnectionContext,System.Threading.CancellationToken,System.Threading.Tasks.ValueTask<System.IO.Stream>>? ConnectCallback { get; set; }

Property Value

Func<SocketsHttpConnectionContext,CancellationToken,ValueTask<Stream>>

A callback method to create a stream.

Examples

The following code example sets TCP KeepAlive on the underlying Socket.

C#

static async Task Main()
{
    using SocketsHttpHandler handler = new SocketsHttpHandler();

    handler.ConnectCallback = async (ctx, ct) =>
    {
        DnsEndPoint dnsEndPoint = ctx.DnsEndPoint;
        IPAddress[] addresses = await Dns.GetHostAddressesAsync(dnsEndPoint.Host, dnsEndPoint.AddressFamily, ct);
        var s = new Socket(SocketType.Stream, ProtocolType.Tcp) { NoDelay = true };
        try
        {
            s.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive, true);
            s.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveTime, 5);
            s.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveInterval, 5);
            s.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveRetryCount, 5);

            await s.ConnectAsync(addresses, dnsEndPoint.Port, ct);
            return new NetworkStream(s, ownsSocket: true);
        }
        catch
        {
            s.Dispose();
            throw;
        }
    };

    // Create an HttpClient object
    using HttpClient client = new HttpClient(handler);

    // Call asynchronous network methods in a try/catch block to handle exceptions
    try
    {
        HttpResponseMessage response = await client.GetAsync("https://learn.microsoft.com/");

        response.EnsureSuccessStatusCode();

        string responseBody = await response.Content.ReadAsStringAsync();
        Console.WriteLine($"Read {responseBody.Length} characters");
    }
    catch (HttpRequestException e)
    {
        Console.WriteLine("\nException Caught!");
        Console.WriteLine($"Message: {e.Message} ");
    }
}

Applies to