From 9d56717be4fa5d0c05e42bb1137b30ef121960d8 Mon Sep 17 00:00:00 2001
From: Jan Tattermusch <jtattermusch@google.com>
Date: Fri, 26 May 2017 14:19:23 -0700
Subject: [PATCH 1/3] throw if server started with unbound ports

---
 src/csharp/Grpc.Core/Server.cs | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/csharp/Grpc.Core/Server.cs b/src/csharp/Grpc.Core/Server.cs
index 63c1d9cd00f..7ba204a0b6f 100644
--- a/src/csharp/Grpc.Core/Server.cs
+++ b/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()
         {
@@ -163,7 +165,8 @@ namespace Grpc.Core
                 GrpcPreconditions.CheckState(!startRequested);
                 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;

From 67206428a41124abcde3798fa39728064ef59ff8 Mon Sep 17 00:00:00 2001
From: Jan Tattermusch <jtattermusch@google.com>
Date: Fri, 26 May 2017 14:28:39 -0700
Subject: [PATCH 2/3] add StartThrowsWithUnboundPortTest

---
 src/csharp/Grpc.Core.Tests/ServerTest.cs | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/csharp/Grpc.Core.Tests/ServerTest.cs b/src/csharp/Grpc.Core.Tests/ServerTest.cs
index 3b51aa63300..5e95ed9ea61 100644
--- a/src/csharp/Grpc.Core.Tests/ServerTest.cs
+++ b/src/csharp/Grpc.Core.Tests/ServerTest.cs
@@ -32,6 +32,7 @@
 #endregion
 
 using System;
+using System.IO;
 using System.Linq;
 using Grpc.Core;
 using Grpc.Core.Internal;
@@ -80,6 +81,21 @@ namespace Grpc.Core.Tests
             server.ShutdownAsync().Wait();
         }
 
+        [Test]
+        public void StartThrowsWithUnboundPorts()
+        {
+            int twiceBoundPort = 9999;
+            Server server = new Server(new[] { new ChannelOption(ChannelOptions.SoReuseport, 0) })
+            {
+                Ports = {
+                    new ServerPort("localhost", twiceBoundPort, ServerCredentials.Insecure),
+                    new ServerPort("localhost", twiceBoundPort, ServerCredentials.Insecure)
+                }
+            };
+            Assert.Throws(typeof(IOException), () => server.Start());
+            server.ShutdownAsync().Wait();
+        }
+
         [Test]
         public void CannotModifyAfterStarted()
         {

From c4096469299bb9d417b7a3ebacea1dbfd31ed34f Mon Sep 17 00:00:00 2001
From: Jan Tattermusch <jtattermusch@google.com>
Date: Thu, 1 Jun 2017 21:56:24 +0200
Subject: [PATCH 3/3] improve exception message

---
 src/csharp/Grpc.Core/Server.cs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/csharp/Grpc.Core/Server.cs b/src/csharp/Grpc.Core/Server.cs
index 7ba204a0b6f..1fb5c62c8fb 100644
--- a/src/csharp/Grpc.Core/Server.cs
+++ b/src/csharp/Grpc.Core/Server.cs
@@ -326,9 +326,11 @@ namespace Grpc.Core
         {
             lock (myLock)
             {
-                if (!ports.All((port) => port.BoundPort != 0))
+                var unboundPort = ports.FirstOrDefault(port => port.BoundPort == 0);
+                if (unboundPort != null)
                 {
-                    throw new IOException("Failed to bind some of ports exposed by the server.");
+                    throw new IOException(
+                        string.Format("Failed to bind port \"{0}:{1}\"", unboundPort.Host, unboundPort.Port));
                 }
             }
         }