[转] C# 获取本机可用端口

当我们要创建一个Tcp/UDP Server connection ,我们需要一个范围在1000到65535之间的端口 。但是本机一个端口只能一个程序监听，所以我们进行本地监听的时候需要检测端口是否被占用。命名空间System.Net.NetworkInformation下定义了一个名为IPGlobalProperties的类，我们使用这个类可以获取所有的监听连接，然后判断端口是否被占用。

  1 //-----------------------------------------------------------------------------
  2 // Filename: FreePort.cs
  3 //
  4 // Description: Helper methods to find the next free UDP and TCP ports.
  5 //
  6 // History:
  7 // 28 Mar 2012    Aaron Clauson    Copied from http://www.mattbrindley.com/developing/windows/net/detecting-the-next-available-free-tcp-port/.
  8 //-----------------------------------------------------------------------------
  9
 10 using System;
 11 using System.Collections.Generic;
 12 using System.Linq;
 13 using System.Net;
 14 using System.Net.NetworkInformation;
 15 using System.Text;
 16 using System.Threading;
 17
 18 namespace SIPSorcery.Sys.Net
 19 {
 20     public class FreePort
 21     {
 22         private const string PortReleaseGuid = "8875BD8E-4D5B-11DE-B2F4-691756D89593";
 23
 24         /// <summary>
 25         /// Check if startPort is available, incrementing and
 26         /// checking again if it‘s in use until a free port is found
 27         /// </summary>
 28         /// <param name="startPort">The first port to check</param>
 29         /// <returns>The first available port</returns>
 30         public static int FindNextAvailableTCPPort(int startPort)
 31         {
 32             int port = startPort;
 33             bool isAvailable = true;
 34
 35             var mutex = new Mutex(false,
 36                 string.Concat("Global/", PortReleaseGuid));
 37             mutex.WaitOne();
 38             try
 39             {
 40                 IPGlobalProperties ipGlobalProperties =
 41                     IPGlobalProperties.GetIPGlobalProperties();
 42                 IPEndPoint[] endPoints =
 43                     ipGlobalProperties.GetActiveTcpListeners();
 44
 45                 do
 46                 {
 47                     if (!isAvailable)
 48                     {
 49                         port++;
 50                         isAvailable = true;
 51                     }
 52
 53                     foreach (IPEndPoint endPoint in endPoints)
 54                     {
 55                         if (endPoint.Port != port) continue;
 56                         isAvailable = false;
 57                         break;
 58                     }
 59
 60                 } while (!isAvailable && port < IPEndPoint.MaxPort);
 61
 62                 if (!isAvailable)
 63                     throw new ApplicationException("Not able to find a free TCP port.");
 64
 65                 return port;
 66             }
 67             finally
 68             {
 69                 mutex.ReleaseMutex();
 70             }
 71         }
 72
 73         /// <summary>
 74         /// Check if startPort is available, incrementing and
 75         /// checking again if it‘s in use until a free port is found
 76         /// </summary>
 77         /// <param name="startPort">The first port to check</param>
 78         /// <returns>The first available port</returns>
 79         public static int FindNextAvailableUDPPort(int startPort)
 80         {
 81             int port = startPort;
 82             bool isAvailable = true;
 83
 84             var mutex = new Mutex(false,
 85                 string.Concat("Global/", PortReleaseGuid));
 86             mutex.WaitOne();
 87             try
 88             {
 89                 IPGlobalProperties ipGlobalProperties =
 90                     IPGlobalProperties.GetIPGlobalProperties();
 91                 IPEndPoint[] endPoints =
 92                     ipGlobalProperties.GetActiveUdpListeners();
 93
 94                 do
 95                 {
 96                     if (!isAvailable)
 97                     {
 98                         port++;
 99                         isAvailable = true;
100                     }
101
102                     foreach (IPEndPoint endPoint in endPoints)
103                     {
104                         if (endPoint.Port != port)
105                             continue;
106                         isAvailable = false;
107                         break;
108                     }
109
110                 } while (!isAvailable && port < IPEndPoint.MaxPort);
111
112                 if (!isAvailable)
113                     throw new ApplicationException("Not able to find a free TCP port.");
114
115                 return port;
116             }
117             finally
118             {
119                 mutex.ReleaseMutex();
120             }
121         }
122     }
123 }