在 .NET 中查找下一个 TCP 端口

这是我一直在寻找的：

static int FreeTcpPort()
{
  TcpListener l = new TcpListener(IPAddress.Loopback, 0);
  l.Start();
  int port = ((IPEndPoint)l.LocalEndpoint).Port;
  l.Stop();
  return port;
}

使用端口号 0。TCP 堆栈将分配下一个空闲端口。

这是一个与 TheSeeker 接受的答案相当的解决方案。虽然我认为它更具可读性：

using System;
using System.Net;
using System.Net.Sockets;

    private static readonly IPEndPoint DefaultLoopbackEndpoint = new IPEndPoint(IPAddress.Loopback, port: 0);

    public static int GetAvailablePort()
    {
        using (var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
        {
            socket.Bind(DefaultLoopbackEndpoint);
            return ((IPEndPoint)socket.LocalEndPoint).Port;
        }
    }

我从 Selenium.WebDriver DLL 中找到了以下代码

命名空间：OpenQA.Selenium.Internal

类别：PortUtility

public static int FindFreePort()
{
    int port = 0;
    Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
    try
    {
        IPEndPoint localEP = new IPEndPoint(IPAddress.Any, 0);
        socket.Bind(localEP);
        localEP = (IPEndPoint)socket.LocalEndPoint;
        port = localEP.Port;
    }
    finally
    {
        socket.Close();
    }
    return port;
}

如果您只想提供一个起始端口，并让它返回下一个可用的 TCP 端口，请使用如下代码：

public static int GetAvailablePort(int startingPort)
{
    var portArray = new List<int>();

    var properties = IPGlobalProperties.GetIPGlobalProperties();

    // Ignore active connections
    var connections = properties.GetActiveTcpConnections();
    portArray.AddRange(from n in connections
                        where n.LocalEndPoint.Port >= startingPort
                        select n.LocalEndPoint.Port);

    // Ignore active tcp listners
    var endPoints = properties.GetActiveTcpListeners();
    portArray.AddRange(from n in endPoints
                        where n.Port >= startingPort
                        select n.Port);

    // Ignore active UDP listeners
    endPoints = properties.GetActiveUdpListeners();
    portArray.AddRange(from n in endPoints
                        where n.Port >= startingPort
                        select n.Port);

    portArray.Sort();

    for (var i = startingPort; i < UInt16.MaxValue; i++)
        if (!portArray.Contains(i))
            return i;

    return 0;
}

首先打开端口，然后将正确的端口号提供给其他进程。

否则，仍然有可能其他进程先打开端口，而您仍然有另一个进程。

如果您想在给定范围内找到下一个可用的 TCP 端口，这里有一种更简洁的实现方式：

private int GetNextUnusedPort(int min, int max)
{
    if (max < min)
        throw new ArgumentException("Max cannot be less than min.");

    var ipProperties = IPGlobalProperties.GetIPGlobalProperties();

    var usedPorts =
        ipProperties.GetActiveTcpConnections()
            .Where(connection => connection.State != TcpState.Closed)
            .Select(connection => connection.LocalEndPoint)
            .Concat(ipProperties.GetActiveTcpListeners())
            .Concat(ipProperties.GetActiveUdpListeners())
            .Select(endpoint => endpoint.Port)
            .ToArray();

    var firstUnused =
        Enumerable.Range(min, max - min)
            .Where(port => !usedPorts.Contains(port))
            .Select(port => new int?(port))
            .FirstOrDefault();

    if (!firstUnused.HasValue)
        throw new Exception($"All local TCP ports between {min} and {max} are currently in use.");

    return firstUnused.Value;
}

如果您想获得特定范围内的空闲端口以将其用作本地端口/端点：

private int GetFreePortInRange(int PortStartIndex, int PortEndIndex)
{
    DevUtils.LogDebugMessage(string.Format("GetFreePortInRange, PortStartIndex: {0} PortEndIndex: {1}", PortStartIndex, PortEndIndex));
    try
    {
        IPGlobalProperties ipGlobalProperties = IPGlobalProperties.GetIPGlobalProperties();

        IPEndPoint[] tcpEndPoints = ipGlobalProperties.GetActiveTcpListeners();
        List<int> usedServerTCpPorts = tcpEndPoints.Select(p => p.Port).ToList<int>();

        IPEndPoint[] udpEndPoints = ipGlobalProperties.GetActiveUdpListeners();
        List<int> usedServerUdpPorts = udpEndPoints.Select(p => p.Port).ToList<int>();

        TcpConnectionInformation[] tcpConnInfoArray = ipGlobalProperties.GetActiveTcpConnections();
        List<int> usedPorts = tcpConnInfoArray.Where(p=> p.State != TcpState.Closed).Select(p => p.LocalEndPoint.Port).ToList<int>();

        usedPorts.AddRange(usedServerTCpPorts.ToArray());
        usedPorts.AddRange(usedServerUdpPorts.ToArray());

        int unusedPort = 0;

        for (int port = PortStartIndex; port < PortEndIndex; port++)
        {
            if (!usedPorts.Contains(port))
            {
                unusedPort = port;
                break;
            }
        }
        DevUtils.LogDebugMessage(string.Format("Local unused Port:{0}", unusedPort.ToString()));

        if (unusedPort == 0)
        {
            DevUtils.LogErrorMessage("Out of ports");
            throw new ApplicationException("GetFreePortInRange, Out of ports");
        }

        return unusedPort;
    }
    catch (Exception ex)
    {
        string errorMessage = ex.Message;
        DevUtils.LogErrorMessage(errorMessage);
        throw;
    }
}


private int GetLocalFreePort()
{
    int hemoStartLocalPort = int.Parse(DBConfig.GetField("Site.Config.hemoStartLocalPort"));
    int hemoEndLocalPort = int.Parse(DBConfig.GetField("Site.Config.hemoEndLocalPort"));
    int localPort = GetFreePortInRange(hemoStartLocalPort, hemoEndLocalPort);
    DevUtils.LogDebugMessage(string.Format("Local Free Port:{0}", localPort.ToString()));
    return localPort;
}


public void Connect(string host, int port)
{
    try
    {
        // Create socket
        Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        //socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);

        var localPort = GetLocalFreePort();
        // Create an endpoint for the specified IP on any port
        IPEndPoint bindEndPoint = new IPEndPoint(IPAddress.Any, localPort);

        // Bind the socket to the endpoint
        socket.Bind(bindEndPoint);

        // Connect to host
        socket.Connect(IPAddress.Parse(host), port);

        socket.Dispose();
    }
    catch (SocketException ex)
    {
        // Get the error message
        string errorMessage = ex.Message;
        DevUtils.LogErrorMessage(errorMessage);
    }
}


public void Connect2(string host, int port)
{
    try
    {
        // Create socket

        var localPort = GetLocalFreePort();

        // Create an endpoint for the specified IP on any port
        IPEndPoint bindEndPoint = new IPEndPoint(IPAddress.Any, localPort);

        var client = new TcpClient(bindEndPoint);
        //client.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true); //will release port when done

        // Connect to the host
        client.Connect(IPAddress.Parse(host), port);

        client.Close();
    }
    catch (SocketException ex)
    {
        // Get the error message
        string errorMessage = ex.Message;
        DevUtils.LogErrorMessage(errorMessage);
    }
}