HttpClient connection state remains in TIME_WAIT after use for a while causing Socket Exception

Question

We are using HttpClient to access the WebAPI hosted on another server. We have a MVC5 application which is getting data form WebAPI window server 2012 R2 with IIS 8.5

Below is the code which using to get data from webapi

//creating static instance of http client
private static HttpClient client = new HttpClient();

//static method to add common header
static ApiCall()
{
   client.DefaultRequestHeaders.Add("Authorization", 
                 string.Format("Value {0}", AppSettings.ApiSecurityKey));
   client.DefaultRequestHeaders.ConnectionClose = true;
}

//finally posting data to the api
//objprop contains the data and other setting
string url = "apiurl";
var postContent = new StringContent(objprop.DataForPost, 
      System.Text.Encoding.UTF8, objprop.ContentType);
response = client.PostAsync(url, postContent).Result;

But during the PT test I am getting multiple request in TIME_WAIT state. Due to this we are getting socket exception.

What are the best practices to use HttpClient?

Is there any setting which can release the socket after the use.

Similar Question is here
1. How do I prevent Socket/Port Exhaustion?
2. Why does HttpClient leave sockets open?
but it did not helped me.

Edit 1 More detail

: InnerException- System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: Only one usage of each socket address (protocol/network address/port) is normally permitted x.x.x:80 at System.Net.Sockets.Socket.InternalEndConnect(IAsyncResult asyncResult) at System.Net.Sockets.Socket.EndConnect(IAsyncResult asyncResult) at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Exception& exception) --- End of inner exception stack trace --- at System.Net.HttpWebRequest.EndGetRequestStream(IAsyncResult asyncResult, TransportContext& context) at System.Net.Http.HttpClientHandler.GetRequestStreamCallback(IAsyncResult ar) --- End of inner exception stack trace --- : URL- http://x.x.x.com//api/GetMenu

Answer 1

Your usage of HttpClient is correct; although its better to use async all the way up as some have commented, its not the cause of your error.

TIME_WAIT is a mandatory phase of a TCP/IP connection; once a connection is established, the side that initiates connection close will go into this state for a preconfigured time.

TCP/IP has a limited pool of ports for connections in and out.

New connections use a subset of these (aka dynamic or ephemeral port range) to allocate a port on each side.

Your app gets error "Address in use" when trying to create a new outgoing connection, but TCP has run out of local ports in the dynamic range.

Depending on which end initiates connection close, it may be your client or server which runs out of ports.

This article from Microsoft details how to modify Windows TCP/IP settings for high connection rates:

• Change TIME_WAIT period from 120 to 30 seconds
• Increase the dynamic port count from 16384 to 64511

Doing both of these will increase the max connection rate from 136 connections/second to about 2150.

Answer 2

After much checking around, using wireshark and telnet -n 5 I found an efficient way to keep socket use down from httpClient was to write my own POST socket method.

    private void PostSocket(MyObject o)
    {
        string host = "localhost";
        int port = 9876;
        
        IPAddress ipAddress = IPAddress.Parse("127.0.0.1");
        IPEndPoint remoteEP = new IPEndPoint(ipAddress, port);

        // Create a TCP socket
        Socket sock = new Socket(ipAddress.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
        sock.Connect(remoteEP);

        // The ToJson uses Newtonsoft method
        var data = new StringContent(o.ToJson(o), Encoding.UTF8, "application/json");
        byte[] byteData = data.ReadAsByteArrayAsync().Result;

        var post = $"POST /prices HTTP/1.1" + Environment.NewLine;
        post += "Content-Type: application/json" + Environment.NewLine;
        post += "Host: " + host + ":" + port + Environment.NewLine;
        post += "Content-Length: " + byteData.Length + Environment.NewLine;
        // This extra newline is required
        post += Environment.NewLine;
        byte[] postData = Encoding.UTF8.GetBytes(post);

        byte[] sendData = new byte[byteData.Length + postData.Length];
        Array.Copy(postData, 0, sendData, 0, postData.Length);
        Array.Copy(byteData, 0, sendData, postData.Length, byteData.Length);

        // Minimum socket send timeout
        sock.SendTimeout = 500;
        sock.Send(sendData);
        
        // If this is not set to false it hangs
        sock.Disconnect(false);
    }