C# 获取空闲端口及查看已用端口

 /// <summary>

        /// 获取第一个可用的端口号

        /// </summary>

        /// <returns></returns>

        public static int GetFirstAvailablePort()

        {

            int MAX_PORT = 65535; //系统tcp/udp端口数最大是65535            

            int BEGIN_PORT = 5000;//从这个端口开始检测



            for (int i = BEGIN_PORT; i < MAX_PORT; i++)

            {

                if (PortIsAvailable(i)) return i;

            }



            return -1;

        }



        /// <summary>

        /// 获取操作系统已用的端口号

        /// </summary>

        /// <returns></returns>

        public static IList PortIsUsed()

        {

            //获取本地计算机的网络连接和通信统计数据的信息

            IPGlobalProperties ipGlobalProperties = IPGlobalProperties.GetIPGlobalProperties();



            //返回本地计算机上的所有Tcp监听程序

            IPEndPoint[] ipsTCP = ipGlobalProperties.GetActiveTcpListeners();



            //返回本地计算机上的所有UDP监听程序

            IPEndPoint[] ipsUDP = ipGlobalProperties.GetActiveUdpListeners();



            //返回本地计算机上的Internet协议版本4(IPV4 传输控制协议(TCP)连接的信息。

            TcpConnectionInformation[] tcpConnInfoArray = ipGlobalProperties.GetActiveTcpConnections();



            IList allPorts = new ArrayList();

            foreach (IPEndPoint ep in ipsTCP) allPorts.Add(ep.Port);

            foreach (IPEndPoint ep in ipsUDP) allPorts.Add(ep.Port);

            foreach (TcpConnectionInformation conn in tcpConnInfoArray) allPorts.Add(conn.LocalEndPoint.Port);



            return allPorts;

        }



        /// <summary>

        /// 检查指定端口是否已用

        /// </summary>

        /// <param name="port"></param>

        /// <returns></returns>

        public static bool PortIsAvailable(int port)

        {

            bool isAvailable = true;



            IList portUsed = PortIsUsed();



            foreach (int p in portUsed)

            {

                if (p == port)

                {

                    isAvailable = false; break;

                }

            }



            return isAvailable;

        }

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