Log status of port before starting server with SelfHostDeployer (#993)

src/Microsoft.AspNetCore.Server.IntegrationTesting/Common/PortHelper.cs

@@ -0,0 +1,77 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using Microsoft.Extensions.Logging;
+
+namespace Microsoft.AspNetCore.Server.IntegrationTesting
+{
+    public class PortHelper
+    {
+        public static void LogPortStatus(ILogger logger, int port)
+        {
+            logger.LogInformation("Checking for processes currently using port {0}", port);
+
+            var psi = new ProcessStartInfo
+            {
+                RedirectStandardOutput = true,
+                RedirectStandardError = true,
+            };
+
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                psi.FileName = "cmd";
+                psi.Arguments = $"/C netstat -nq | find \"{port}\"";
+            }
+            else
+            {
+                psi.FileName = "lsof";
+                psi.Arguments = $"-i :{port}";
+            }
+
+            var process = new Process
+            {
+                StartInfo = psi,
+                EnableRaisingEvents = true
+            };
+
+            var linesLogged = false;
+
+            process.OutputDataReceived += (sender, data) =>
+            {
+                if (!string.IsNullOrWhiteSpace(data.Data))
+                {
+                    linesLogged = true;
+                    logger.LogInformation("portstatus: {0}", data.Data);
+                }
+            };
+            process.ErrorDataReceived += (sender, data) =>
+            {
+                if (!string.IsNullOrWhiteSpace(data.Data))
+                {
+                    logger.LogWarning("portstatus: {0}", data.Data);
+                }
+            };
+
+            try
+            {
+                process.Start();
+                process.BeginErrorReadLine();
+                process.BeginOutputReadLine();
+                process.WaitForExit();
+
+                if (!linesLogged)
+                {
+                    logger.LogInformation("portstatus: it appears the port {0} is not in use.", port);
+                }
+            }
+            catch (Exception ex)
+            {
+                logger.LogWarning("Failed to check port status. Executed: {0} {1}\nError: {2}", psi.FileName, psi.Arguments, ex.ToString());
+            }
+            return;
+        }
+    }
+}

src/Microsoft.AspNetCore.Server.IntegrationTesting/Deployers/SelfHostDeployer.cs

@@ -83,6 +83,12 @@ namespace Microsoft.AspNetCore.Server.IntegrationTesting
                 executableArgs = $"run --framework {targetFramework} {DotnetArgumentSeparator}";
             }
 
+            if (uri.Port != 0)
+            {
+                // shows output from netstat/lsof. May be useful if the port is already in use
+                PortHelper.LogPortStatus(Logger, uri.Port);
+            }
+
             executableArgs += $" --server.urls {uri} "
             + $" --server {(DeploymentParameters.ServerType == ServerType.WebListener ? "Microsoft.AspNetCore.Server.HttpSys" : "Microsoft.AspNetCore.Server.Kestrel")}";
 
@@ -148,4 +154,4 @@ namespace Microsoft.AspNetCore.Server.IntegrationTesting
             StopTimer();
         }
     }
-}
+}