For Windows XP Pro, the most efficient way to check port usage is through command line utilities. Here are the essential commands:

netstat -ano | findstr "8080"  // Replace 8080 with your target port

This will output something like:

TCP    0.0.0.0:8080          0.0.0.0:0              LISTENING       1234

Once you have the PID (1234 in above example), use:

tasklist /FI "PID eq 1234"

For .NET remoting applications specifically, you might see:

Image Name                     PID Session Name        Mem Usage
========================= ======== ================ ============
YourApp.exe                  1234 Console                 45,828 K

For those preferring graphical tools:

1. Download TCPView from Sysinternals
2. Run the executable (no installation needed)
3. Locate your port in the list

To verify if your .NET remoting channel is properly registered:

// C# code snippet to check registered channels
foreach (IChannel channel in ChannelServices.RegisteredChannels)
{
    Console.WriteLine($"Channel: {channel.ChannelName}");
    if (channel is TcpChannel tcpChannel)
    {
        Console.WriteLine($"Port: {tcpChannel.GetChannelUri()}");
    }
}

If you're not seeing expected results:

• Run commands as Administrator
• Check firewall settings (even on localhost)
• Verify your .NET remoting configuration in app.config

For Windows XP, you might need to install PowerShell 2.0:

# PowerShell port checker
$port = 8080
$process = Get-NetTCPConnection -LocalPort $port | Select-Object -ExpandProperty OwningProcess
Get-Process -Id $process | Format-Table Id, ProcessName, Path

The most reliable way to check port usage on Windows XP is through the command-line tool netstat. Open Command Prompt and run:

netstat -ano

This will display all active connections and listening ports with their associated Process IDs (PIDs). The -a shows all connections, -n displays addresses numerically, and -o shows process IDs.

Once you have the PID from netstat, you can identify the application using Task Manager:

1. Press Ctrl+Shift+Esc to open Task Manager
2. Go to the Processes tab
3. Enable "PID" column (View > Select Columns)
4. Match the PID from netstat

For .NET Remoting specifically, you might see either your application's process or svchost.exe if it's hosted in a Windows service.

If you have PowerShell installed, this one-liner can help:

Get-NetTCPConnection | Where-Object {$_.LocalPort -eq YOUR_PORT_NUMBER} | Select-Object LocalAddress,LocalPort,State,OwningProcess

Then find the process using:

Get-Process -Id PID_NUMBER

For programmatic checking within your .NET application:

using System.Net;
using System.Net.NetworkInformation;

public bool IsPortInUse(int port) {
    IPGlobalProperties ipProperties = IPGlobalProperties.GetIPGlobalProperties();
    IPEndPoint[] endpoints = ipProperties.GetActiveTcpListeners();
    return endpoints.Any(endpoint => endpoint.Port == port);
}

When debugging .NET Remoting applications:

• Ensure your channel is properly registered: ChannelServices.RegisteredChannels
• Check firewall exceptions for your port
• Verify the remoting object is correctly configured in app.config

For deeper analysis:

• TCPView: Graphical tool showing all TCP/UDP endpoints
• Wireshark: Packet analysis to see actual traffic
• PortQry: Microsoft's advanced port query tool