Workaround for a bug in .NET Core. This issue is referenced by #92. It is has been reported to the dotnet corefx team here: dotnet/corefx#8809 The issue won't be resolved in 1.0.0, so @stephentoub recommended that we reuse the HttpClient.

src/Microsoft.AspNetCore.NodeServices/HostingModels/HttpNodeInstance.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Net;
 using System.Net.Http;
 using System.Text;
 using System.Text.RegularExpressions;
@@ -19,6 +18,8 @@ namespace Microsoft.AspNetCore.NodeServices
             ContractResolver = new CamelCasePropertyNamesContractResolver()
         };
 
+	    private HttpClient _client;
+        private bool _disposed;
         private int _portNumber;
 
         public HttpNodeInstance(string projectPath, int port = 0, string[] watchFileExtensions = null)
@@ -29,6 +30,7 @@ namespace Microsoft.AspNetCore.NodeServices
                 projectPath,
                 MakeCommandLineOptions(port, watchFileExtensions))
         {
+            _client = new HttpClient();
 		}
 
         private static string MakeCommandLineOptions(int port, string[] watchFileExtensions)
@@ -46,12 +48,10 @@ namespace Microsoft.AspNetCore.NodeServices
         {
             await EnsureReady();
 
-            using (var client = new HttpClient())
-            {
             // TODO: Use System.Net.Http.Formatting (PostAsJsonAsync etc.)
             var payloadJson = JsonConvert.SerializeObject(invocationInfo, JsonSerializerSettings);
             var payload = new StringContent(payloadJson, Encoding.UTF8, "application/json");
-                var response = await client.PostAsync("http://localhost:" + _portNumber, payload);
+            var response = await _client.PostAsync("http://localhost:" + _portNumber, payload);
             var responseString = await response.Content.ReadAsStringAsync();
 
             if (!response.IsSuccessStatusCode)
@@ -74,7 +74,6 @@ namespace Microsoft.AspNetCore.NodeServices
 
             return (T)(object)responseString;
         }
-        }
 
         protected override void OnOutputDataReceived(string outputData)
         {
@@ -94,5 +93,19 @@ namespace Microsoft.AspNetCore.NodeServices
             // Prepare to receive a new port number
             _portNumber = 0;
         }
+
+	    protected override void Dispose(bool disposing) {
+	        base.Dispose(disposing);
+
+	        if (!_disposed)
+            {
+	            if (disposing)
+                {
+	                _client.Dispose();
+	            }
+
+	            _disposed = true;
+	        }
+	    }
 	}
 }