How to find which process is listening on a TCP or UDP port on windows

To determine which process is listening on a specific TCP or UDP port on Windows, you can use several built-in command-line tools and utilities. This is particularly useful for diagnosing network-related issues, identifying conflicting services, or ensuring that the intended application is correctly binding to its designated port. By leveraging these tools, you can effectively pinpoint the process associated with a port and take appropriate actions if necessary.

Using Command Prompt and Netstat

Netstat command: Netstat (network statistics) is a command-line tool available in Windows that provides information about network connections, routing tables, interface statistics, masquerade connections, and multicast memberships. To find which process is using a specific port, open Command Prompt and use the following command:

netstat -ano | findstr :

Replace ` with the actual port number you want to check, such as 80 for HTTP or 443 for HTTPS. The-aoption displays all connections and listening ports,-nshows addresses and port numbers in numerical form,-odisplays the owning process ID associated with each connection, andfindstr` filters the output to show only the lines containing the specified port number.

Example: To find which process is listening on port 8080, you would run:

netstat -ano | findstr :8080

The output will display the protocol (TCP or UDP), local address (including the port number), foreign address (if applicable), state of the connection, and the Process ID (PID) of the owning process.

Task Manager for Process Identification

Using Task Manager: Once you have identified the Process ID (PID) from the netstat output, you can match it with the corresponding process in Task Manager to gather more information or terminate the process if needed.

1. Open Task Manager: Press Ctrl + Shift + Esc or right-click on the taskbar and select Task Manager.
2. View Process Details: Go to the Details tab in Task Manager.
3. Locate Process by PID: Locate the process by its Process ID (PID) column, which you found using netstat.

PowerShell Commandlet: Get-NetTCPConnection and Get-NetUDPConnection

Using PowerShell: PowerShell provides more advanced cmdlets (Get-NetTCPConnection and Get-NetUDPConnection) that allow you to directly query TCP and UDP connections, respectively, and filter by specific properties such as local port number.

# For TCP connections
Get-NetTCPConnection -LocalPort 

# For UDP connections
Get-NetUDPConnection -LocalPort 

Replace “ with the port number you want to check. These cmdlets provide detailed information about connections, including the Process ID (PID) and more.

Example: To find which process is using port 8080 with PowerShell:

# For TCP connections
Get-NetTCPConnection -LocalPort 8080

# For UDP connections
Get-NetUDPConnection -LocalPort 8080

The output will include the OwningProcess property, which indicates the PID of the process using the specified port.

Using Resource Monitor

Resource Monitor: Resource Monitor is another built-in Windows utility that provides more detailed information about processes and their network activity, including listening ports.

1. Open Resource Monitor: Type resmon in the Run dialog (Win + R) and press Enter.
2. Network Tab: Go to the Network tab in Resource Monitor.
3. Listening Ports: Under the Listening Ports section, locate the port number you are interested in.
4. Process ID: The PID column shows the Process ID of the process listening on each port.

Third-Party Tools for Detailed Analysis

Advanced tools: For more advanced network analysis and troubleshooting, consider using third-party tools such as Wireshark, TCPView, or Process Explorer. These tools offer extensive capabilities for monitoring network connections, including detailed information about processes associated with specific ports.

Considerations and Permissions

Administrative rights: Some commands and tools require administrative privileges to access detailed process information, especially Process IDs (PIDs). Ensure you run Command Prompt or PowerShell as an administrator (Run as administrator) to get complete and accurate results.

Multiple instances: Keep in mind that multiple instances of a process or multiple processes can listen on the same port, depending on the configuration and network requirements of applications. Ensure you are identifying the correct process based on your specific use case and requirements.

Summary

Identifying which process is listening on a TCP or UDP port on Windows involves using built-in command-line tools like netstat and PowerShell cmdlets, as well as utilities like Task Manager and Resource Monitor. These tools provide different levels of detail and flexibility depending on your needs, whether for basic troubleshooting or detailed network analysis. By leveraging these tools effectively, you can accurately pinpoint the process associated with a specific port, diagnose network-related issues, and take appropriate actions to manage and optimize your system’s network resources.