TCPView

Quick Guide: How to Use TCPView to Monitor Network ConnectionsTCPView is a lightweight, free utility from Microsoft’s Sysinternals suite that displays a detailed, real-time list of all TCP and UDP endpoints on your Windows computer. It shows the local and remote addresses, the state of TCP connections, the owning process, and process IDs — making it a powerful tool for diagnosing network issues, spotting suspicious connections, and understanding application behavior.

What TCPView shows (at a glance)

• Process name and PID — which program owns the connection.
• Protocol — TCP or UDP.
• Local address and port — where your system is listening or sending from.
• Remote address and port — the endpoint your system is connected to.
• State — for TCP (e.g., LISTEN, ESTABLISHED, TIME_WAIT).
• Sent/Received bytes (if you enable the statistics view).

Downloading and launching TCPView

1. Go to the Microsoft Sysinternals website and download the TCPView zip package.
2. Extract the contents to a folder. No installation is required — TCPView is portable.
3. Right-click tcpview.exe and choose “Run as administrator” for full visibility of system processes (recommended).
4. After launch, TCPView immediately begins populating the list of network endpoints.

Understanding the interface

• The main window lists each endpoint as one row. Columns include Process, PID, Protocol, Local Address, Remote Address, State, and sometimes additional columns like Process Path or Company Name if available.
• Use the toolbar or menu to pause updates, refresh manually, or configure options. Pausing is useful if you need to examine a transient connection without it disappearing.
• Double-click a row to open the Properties dialog for that connection, which shows more details and offers options such as closing the connection or jumping to the process in Task Manager.

Common tasks and workflows

• Viewing active connections: Sort by the State column to see ESTABLISHED connections. This helps identify which processes are communicating externally.
• Finding which process is listening on a port: Sort or filter by Local Port and State = LISTEN. Useful when diagnosing port conflicts or unexpected services.
• Closing a suspicious connection: Right-click a connection and choose “Close Connection” to terminate that socket. Use caution — closing connections can cause application errors.
• Killing a process: Right-click the process name and choose “Kill Process” to terminate an application that’s misbehaving or has unwanted network activity.
• Resolving IPs to hostnames: Toggle the Resolve Addresses option (View → Resolve Addresses) to map remote IPs to DNS names. This can slow updates, so enable it only when needed.
• Saving logs: File → Save allows exporting the current list to a text file for later analysis or to share with colleagues.

Tips for effective monitoring

• Run as administrator to see all processes, including system services.
• Use the filter (Ctrl+L) to quickly show only rows matching a process name, IP, or port.
• Combine TCPView with Resource Monitor or Process Explorer to correlate network activity with CPU/disk usage and to inspect process details and DLLs.
• Use the Highlight feature (Options → Highlight) to color rows when states change — makes transient events easier to spot.
• For long-term logging, schedule periodic exports and correlate them with other logs (firewall, application logs).

Examples: Real troubleshooting scenarios

1. Slow application with external calls

• Open TCPView and sort by Process. Look for the app and check for ESTABLISHED connections to remote servers. If many connections are in TIME_WAIT, it may indicate frequent short-lived connections; consider connection reuse options in the app.

1. Unknown service listening on port 8080

• Filter Local Port = 8080 and State = LISTEN. Note the Process and PID, double-click to view properties, then use Task Manager or Process Explorer to inspect the executable’s path and publisher.

1. Suspicious outbound connection

• Identify the process making the outbound connection, resolve the remote address to a hostname, and, if malicious, close the connection and kill the process. Then quarantine the executable for further analysis.

Limitations and security considerations

• TCPView is a monitoring and control tool but not an anti-malware product. Use it to spot anomalies, then follow up with antivirus/EDR scans.
• Closing connections or killing processes can cause data loss or instability; perform such actions with understanding of the consequences.
• Resolving addresses may generate DNS queries, which could be logged on your network.

Alternatives and complementary tools

• netstat (built into Windows) — command-line view of connections.
• Resource Monitor (resmon.exe) — integrated with Windows for per-process network, disk, and CPU details.
• Process Explorer — deeper process inspection including handles and loaded modules.
• Wireshark — packet-level network capture for deep protocol analysis.

Quick reference — common TCP states

• LISTEN — waiting for incoming connections.
• SYN_SENT / SYN_RECEIVED — connection handshake in progress.
• ESTABLISHED — active open connection exchanging data.
• FIN_WAIT / CLOSE_WAIT / LAST_ACK — connection closing sequence.
• TIME_WAIT — socket waiting to ensure the remote end received the close.

TCPView is a practical, immediate way to see what your Windows machine is talking to. For day-to-day troubleshooting, security checks, and learning how applications use the network, it provides clear, actionable information without installing complex software.