throw if server started with unbound ports

src/csharp/Grpc.Core/Server.cs

@@ -34,6 +34,7 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
 using Grpc.Core.Internal;
@@ -155,6 +156,7 @@ namespace Grpc.Core
 
         /// <summary>
         /// Starts the server.
+        /// Throws <c>IOException</c> if not successful.
         /// </summary>
         public void Start()
         {
@@ -164,6 +166,7 @@ namespace Grpc.Core
                 GrpcPreconditions.CheckState(!shutdownRequested);
                 startRequested = true;
 
+                CheckPortsBoundSuccessfully();
                 handle.Start();
 
                 for (int i = 0; i < requestCallTokensPerCq; i++)
@@ -316,6 +319,20 @@ namespace Grpc.Core
             }
         }
 
+        /// <summary>
+        /// Checks that all ports have been bound successfully.
+        /// </summary>
+        private void CheckPortsBoundSuccessfully()
+        {
+            lock (myLock)
+            {
+                if (!ports.All((port) => port.BoundPort != 0))
+                {
+                    throw new IOException("Failed to bind some of ports exposed by the server.");
+                }
+            }
+        }
+
         private void DisposeHandle()
         {
             var activeCallCount = activeCallCounter.Count;