C# 获取空闲端口及查看已用端口

转自论坛：http://topic.csdn.net/u/20100603/13/ef349c6e-66ee-4129-a884-61c9091a9a99.html

using System.Net.NetworkInformation;

/// <summary>
/// 获取第一个可用的端口号
/// </summary>
/// <returns></returns>
public static int GetFirstAvailablePort()
{
    int MAX_PORT = 6000; //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;
}