TcpView

TCPView is a command-line utility developed by Sysinternals, now part of Microsoft, that displays detailed listings of all TCP and UDP endpoints on the local system, including the local and remote addresses, state of TCP connections, and the process ID (PID) associated with each endpoint. It provides a real-time view of network activity, allowing users to see which applications are communicating over the network.

The information presented by TCPView includes the process name, PID, protocol (TCP or UDP), local address and port, remote address and port, and the state of the connection for TCP endpoints. This state information can include established, listening, time wait, and closed states, which are crucial for diagnosing network connectivity issues. UDP endpoints are stateless, so their state is not displayed.

TCPView is particularly useful for network administrators and security professionals. It can help identify unauthorized network connections, troubleshoot applications that are not communicating as expected, and understand the network behavior of specific processes. By correlating process information with network endpoints, users can quickly pinpoint which application is responsible for a particular network connection. The utility can be run from the command prompt or as a graphical application. It's a valuable tool for system monitoring and network troubleshooting.