Networking·Amitabh Sarkar·February 2025·5 min read

How to Check If a Port Is Open

Checking whether a port is open tells you if a service is actively listening for network connections on your PC or is accessible from the internet. Whether you're troubleshooting a game server, setting up port forwarding, or diagnosing a connection issue, there are four reliable methods to check open ports — using Command Prompt, PowerShell, browser-based tools, and online port checkers. This guide covers all four, for both Windows and macOS.

Method 1: Check Open Ports with Command Prompt (Windows)

The netstat command lists all active TCP/UDP connections and listening ports on your machine. This shows ports open locally — not necessarily accessible from outside your network.

# List all listening ports with process IDs

netstat -ano

# Check if a specific port (e.g., 8080) is in use

netstat -ano | findstr :8080

# Find which app uses a PID (replace 1234 with actual PID)

tasklist | findstr 1234

In the output, look for LISTENING in the State column. The Local Address column shows the IP and port (e.g., 0.0.0.0:80 means port 80 is open on all interfaces).

Method 2: Check Open Ports with PowerShell

PowerShell provides a more readable output and lets you test connectivity to a specific port on a remote host in one command:

# Test if port 25565 is open on a remote server

Test-NetConnection -ComputerName example.com -Port 25565

# Check your local machine's listening ports

Get-NetTCPConnection -State Listen

# Filter to a specific port

Get-NetTCPConnection -LocalPort 3000

Test-NetConnection returns a TcpTestSucceeded : True result if the remote port is open and accepting connections.

Method 3: Check Open Ports on macOS / Linux

# macOS/Linux: list all listening ports

sudo lsof -i -P -n | grep LISTEN

# Test connectivity to a remote port

nc -zv example.com 25565

# Or using nmap (if installed)

nmap -p 25565 example.com

Method 4: Online Port Checker (External Test)

Local tools only show ports open on your machine — they can't tell you whether those ports are reachable from the internet. For that, you need an external port checker that probes your public IP from outside your network.

To use an online port checker: find your public IP (search "what is my IP" in a browser), then enter your public IP and the port number you want to test. The tool makes a real TCP connection attempt from an external server.

Results: Open = port is accessible from the internet. Closed = your firewall or router is rejecting connections. Timed out / Filtered = firewall is silently dropping the connection probe (stealth mode).

Common Ports Reference

Port	Service	Should Be	Notes
21	FTP	Should be closed	Old file transfer — use SFTP (22) instead
22	SSH	Open if needed	Secure shell — restrict to known IPs
25565	Minecraft	Open if hosting	Default Minecraft Java server port
80	HTTP	Open for web	Standard web server port
443	HTTPS	Open for web	Secure web traffic
3074	Xbox Live	Open for Xbox	Required for NAT Type Open on Xbox
3389	Remote Desktop	Close externally	Major attack target — restrict strictly
3478-3480	PlayStation Network	Open for PS	Required for PSN Open NAT type

For gaming specifically, ports 3074 (Xbox Live) and 3478–3480 (PlayStation Network) must be open for an Open NAT type. If your game server is running and ports are confirmed open, the next step is checking your peripheral performance — use our Mouse Polling Rate Test to verify your mouse is reporting at its rated Hz, and our Reaction Time Test to measure your baseline gaming reflexes.

Frequently Asked Questions

What does it mean for a port to be open?

An open port means a service on your computer is actively listening for incoming network connections on that port number. For example, port 80 being open means a web server is running. A closed port means no service is listening there. A filtered or stealth port means a firewall is blocking attempts to probe it — the connection attempt times out with no response.

How do I check open ports on Windows using CMD?

Open Command Prompt and type: netstat -ano. This lists all active connections and listening ports. The 'LISTENING' state means a port is open for incoming connections. To find which application uses a specific port, note the PID (last column) and run: tasklist | findstr [PID]. You can also use: netstat -ano | findstr :80 to check a specific port number.

Why can't I connect to my server even though the port is open locally?

The most common reason is the port is open on your computer but blocked at your router or firewall. Local tools like netstat show ports open on your machine, not ports accessible from the internet. Use an online port checker to test external accessibility. You may need to configure port forwarding on your router and ensure Windows Firewall allows the port.

What common ports should be open or closed?

Ports that should typically be open on a gaming or home server: 80 (HTTP), 443 (HTTPS), 25565 (Minecraft), 7777 (many game servers), 3074 (Xbox Live), 3478-3480 (PlayStation Network). Ports that should generally be closed externally for security: 21 (FTP), 23 (Telnet), 3389 (RDP/Remote Desktop), 3306 (MySQL), 445 (SMB/Windows file sharing). Open SMB or RDP to the internet is a major security risk.

How do I check if port forwarding is working?

After setting up port forwarding on your router: use an online port checker (search 'open port check tool') and enter your public IP address and the forwarded port number. If it shows 'open', port forwarding is working. If it shows 'closed' or 'timed out', check: the service is actually running on that port, your router's port forwarding rule has the correct internal IP and port, and Windows Firewall isn't blocking the port.

Last updated: April 2026