Some links on this page are affiliate links: if you buy through them we may earn a commission, at no extra cost to you.
Use netstat to inspect ports and sockets on the local computer. The command varies by operating system:
- Windows:
netstat -ano - Linux:
sudo netstat -tulpn - macOS:
netstat -an | grep LISTEN
These commands show local listeners and connections. They do not, by themselves, prove that a port is reachable from another computer or exposed to the public internet.
What does “open port” mean?
“Open port” can describe several different conditions:
- Listening locally: An application has created a socket and is waiting for inbound connections.
- Currently connected: A socket has an active connection, commonly shown as
ESTABLISHED. - Reachable remotely: Another machine can successfully connect to the port.
- Internet-exposed: The port is reachable through the host firewall, router or NAT rules, cloud security groups, and upstream networks.
netstat primarily reports local sockets and connection states. A port can be listening but inaccessible because it is bound to loopback, blocked by a firewall, not forwarded by a router, or restricted by cloud networking.
#1 Best Overall
- 𝐇𝐢𝐠𝐡-𝐒𝐩𝐞𝐞𝐝 𝐔𝐒𝐁 𝐄𝐭𝐡𝐞𝐫𝐧𝐞𝐭 𝐀𝐝𝐚𝐩𝐭𝐞𝐫 - UE306 is a USB 3.0 Type-A to RJ45 Ethernet adapter that adds a reliable wired network port to your laptop, tablet, or Ultrabook. It delivers fast and stable 10/100/1000 Mbps wired connections to your computer or tablet via a router or network switch, making it ideal for file transfers, HD video streaming, online gaming, and video conferencing.
- 𝐔𝐒𝐁 𝟑.𝟎 𝐟𝐨𝐫 𝐅𝐚𝐬𝐭𝐞𝐫, 𝐌𝐨𝐫𝐞 𝐒𝐭𝐚𝐛𝐥𝐞 𝐃𝐚𝐭𝐚 𝐓𝐫𝐚𝐧𝐬𝐟𝐞𝐫𝐬- Powered via USB 3.0, this adapter provides high-speed Gigabit Ethernet without the need for external power(10/100/1000Mbps). Backward compatible with USB 2.0/1.1, it ensures reliable performance across a wide range of devices.
- 𝐒𝐮𝐩𝐩𝐨𝐫𝐭𝐬 𝐍𝐢𝐧𝐭𝐞𝐧𝐝𝐨 𝐒𝐰𝐢𝐭𝐜𝐡- Easily connect your Nintendo Switch to a wired network for faster downloads and a more stable online gaming experience compared to Wi-Fi.
- 𝐏𝐥𝐮𝐠 𝐚𝐧𝐝 𝐏𝐥𝐚𝐲- No driver required for Nintendo Switch, Windows 11/10/8.1/8, and Linux. Simply connect and enjoy instant wired internet access without complicated setup.
- 𝐁𝐫𝐨𝐚𝐝 𝐃𝐞𝐯𝐢𝐜𝐞 𝐂𝐨𝐦𝐩𝐚𝐭𝐢𝐛𝐢𝐥𝐢𝐭𝐲- Supports Nintendo Switch, PCs, laptops, Ultrabooks, tablets, and other USB-powered web devices; works with network equipment including modems, routers, and switches.
Windows: list open and listening ports
Open Command Prompt or PowerShell and run:
netstat -anoThis displays TCP and UDP entries using numeric addresses and ports. The -a option includes active connections and listening ports, -n prevents name resolution, and -o adds the owning process ID.
To show only TCP entries in the listening state:
netstat -ano | findstr LISTENINGTo inspect the executable associated with each connection, use:
netstat -abnoThe -b option can be slow and may require an elevated Command Prompt. It may also fail to show details for protected processes or processes that exit while the command is running. See Microsoft’s netstat documentation for the complete option list and output definitions.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Find the program using a Windows port
For example, to find what is using port 8080:
netstat -ano | findstr :8080Example output:
TCP 0.0.0.0:8080 0.0.0.0:0 LISTENING 1234The final number, 1234, is the PID. Map it to a process with:
tasklist /FI "PID eq 1234"In PowerShell, you can use:
Get-Process -Id 1234You can also inspect TCP connections by local port with:
Rank #2
- Connects a USB 3.0 device (computer/laptop) to a router, modem, or network switch to deliver Gigabit Ethernet to your network connection. Does not support Smart TV or gaming consoles (e.g.Nintendo Switch).
- Supported features include Wake-on-LAN function, Green Ethernet & IEEE 802.3az-2010 (Energy Efficient Ethernet)
- Supports IPv4/IPv6 pack Checksum Offload Engine (COE) to reduce Cental Processing Unit (CPU) loading
- Compatible with Windows 8.1 or higher, Mac OS
Get-NetTCPConnection -LocalPort 443To include the fields most useful for investigation:
Get-NetTCPConnection -LocalPort 443 | Select-Object LocalAddress,LocalPort,RemoteAddress,RemotePort,State,OwningProcessLinux: list listening TCP and UDP ports
The traditional Linux command is:
sudo netstat -tulpnThe options mean:
-t: TCP-u: UDP-l: listening or locally bound sockets-p: process and PID information-n: numeric addresses and ports
Typical output resembles:
Proto Local Address State PID/Program name
tcp 0.0.0.0:22 LISTEN 742/sshdRoot privileges are commonly required to see process ownership for sockets belonging to other users. If the process column is incomplete, rerun the command with sudo. The Linux netstat manual documents this syntax and notes that the utility is obsolete on modern Linux systems.
For TCP listeners only:
sudo netstat -ltnpFor UDP sockets only:
sudo netstat -lunpThe modern Linux alternative: ss
Linux distributions generally prefer ss, which is usually installed by default and is designed to replace netstat:
sudo ss -ltnupThe equivalent commands for a specific port are:
sudo netstat -tulpn | grep ':8080'
sudo ss -ltnup | grep ':8080'ss can provide more socket and TCP-state information and performs better on systems with many sockets. Its syntax differs from netstat; refer to the ss manual for filtering options.
macOS: list listening ports
macOS uses a BSD-derived version of netstat, so Linux options such as -tulpn are not interchangeable with macOS syntax. To list numeric TCP listeners, run:
Rank #3
![BENFEI USB 3.0 to Ethernet Adapter, USB C to RJ45 Gigabit LAN (1000Mbps) Network Adapter, Compatible with MacBook/Pro/Air, Surface Pro, Windows 11/10/8/7, Mac OS [Aluminium Shell&Nylon Cable]](https://m.media-amazon.com/images/I/41fk9DHmdwL._SL160_.jpg)
- COMPACT DESIGN - The compact-designed portable BENFEI USB A/C to Ethernet adapter connects your computer or tablet to a router,modem or network switch for network connection. It adds a standard RJ45 port to your Ultrabook, notebook or Macbook Air for file transferring, video conferencing, gaming, and HD video streaming.
- SUPERIOR STABILITY - Built-in advanced IC chip works as the bridge between RJ45 Ethernet cable and your USB A/C devices. The driver-free installation with native driver support in Chrome, Mac, and Windows OS; The USB A/C Ethernet adapter dongle supports important performance features including Wake-on-Lan (WoL), Full-Duplex (FDX) and Half-Duplex (HDX) Ethernet, Crossover Detection, Backpressure Routing, Auto-Correction (Auto MDIX).
- INCREDIBLE PERFORMANCE - Supports full 10/100/1000Mbps gigabit ethernet performance over USB A/C's 5Gbps bus, faster and more reliable than most wireless connections. Link and Activity LEDs. USB powered, no external power required. Backward compatible with USB 2.0/1.1.✅ To reach 1Gbps, make sure to use CAT6 & up Ethernet cables.
- BROAD COMPATIBILITY - The USB A/C-Ethernet adapter is compatible with Windows 11/10/8.1/8/7/Vista/XP, Mac OSX 10.6/10.7/10.8/10.9/10.10/10.11/10.12, Linux kernel 3.x/2.6, Android and Chrome OS.Compatible with IEEE 802.3, IEEE 802.3u and IEEE 802.3ab. Supports IEEE 802.3az (Energy Efficient Ethernet).❌Do Not Support Windows RT. (NOT compatible with Nintendo Switch.)
- 18 MONTH WARRANTY - Exclusive BENFEI Unconditional 18-month Warranty ensures long-time satisfaction of your purchase; Friendly and easy-to-reach customer service to solve your problems timely.
netstat -an | grep LISTENTo look for a particular port:
netstat -an | grep ':443'This is primarily a TCP listener check. UDP does not use TCP’s LISTEN state, so a complete UDP and process inventory requires a separate socket or process-inspection utility. The available flags and output depend on the macOS/BSD implementation; consult the macOS netstat manual.
Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesHow to read netstat output
| Field | Meaning |
|---|---|
| Proto | The protocol, normally TCP or UDP. |
| Local Address | The local interface or address and port used by the socket. |
| Foreign Address | The remote endpoint for a connection, when one exists. |
| State | The TCP connection state. UDP entries generally do not have equivalent TCP states. |
| PID / Program name | The process ID and, where permissions and platform support allow it, the owning program. |
Numeric mode is useful during troubleshooting. Without -n, addresses may be resolved to hostnames and port numbers may be translated into service names. That can slow output and make it harder to compare exact addresses and ports. A service name is only a label from the system’s service database; it does not identify the actual application using the socket.
Common TCP states
- LISTEN or LISTENING: A TCP socket is waiting for inbound connections.
- ESTABLISHED: A TCP connection is active.
- TIME_WAIT: The endpoint is retaining state after a connection closed.
- CLOSE_WAIT: The remote side closed its connection, but the local application has not fully closed its socket.
- SYN_SENT: The computer sent a connection request and is waiting for a response.
- SYN_RECEIVED: A connection request was received and the handshake is in progress.
Do not treat every row that is not LISTEN as an inbound open port. Many such rows represent active, outgoing, or recently closed connections.
Why UDP entries look different
UDP is connectionless. A program can bind to a UDP port without creating a TCP-style listener, so UDP rows may not show LISTEN or ESTABLISHED. When checking for UDP services, inspect the protocol column and locally bound UDP ports rather than filtering only for a TCP state.
Understanding local addresses and exposure
The address on which a service is bound is an important clue:
The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Rank #4
- Ultra-Fast, Rock-Solid: The UGREEN usb to ethernet adapter is engineered for ultra-fast 1000Mbps network speeds. It delivers rock-solid stability and security, helping you boost productivity, unleash smooth gameplay, and browse seamlessly
- Seamless Compatibility with Nintendo Switch: The ethernet to usb adapter is fully compatible with Nintendo Switch and Switch OLED, just connect it to the dock’s ethernet port and dive into ultra-smooth, lag-free gaming
- Plug and Play: The ethernet adapter is driver-free for Windows 11/10/8.1/8, macOS, Chrome OS, and Android. It requires installing the driver on Windows XP/7/Vista and Linux, which you can easily install with our instructions
- Wide Compatibility: The usb to ethernet is compatible with most laptops and desktops featuring USB 3.0 ports, including MacBook Air/Pro, Dell XPS, Surface Book, and more
- Crafted to Last, Designed to Impress: Built with a sturdy aluminum shell for efficient heat dissipation and enhanced durability, the ethernet to usb is designed to last. The cable connection point features reinforced construction for extra strength and reliability. A yellow-green LED indicator keeps you instantly informed of its working status
127.0.0.1:8000usually means the service accepts IPv4 connections only from the same computer.::1:8000is the IPv6 loopback equivalent.0.0.0.0:8000usually means the service is listening on all available IPv4 interfaces.[::]:8000indicates an IPv6 wildcard listener. Whether it also accepts IPv4 connections depends on the operating system and socket configuration.192.168.1.20:8000indicates binding to a particular local interface or address.
A wildcard address does not automatically mean internet exposure. Firewall rules, routing, NAT or port forwarding, cloud security groups, network ACLs, and the presence of a publicly reachable address all matter. Conversely, a loopback-only service is normally inaccessible from other machines even if the application is working correctly.
Refresh the port list
On Windows, refresh the display every five seconds:
netstat -ano 5Stop the command with Ctrl+C.
On Linux, you can use the interval form:
sudo netstat -tulpn 5Or refresh ss every two seconds:
watch -n 2 'sudo ss -ltnup'Repeated sampling helps catch short-lived services or sockets that appear and disappear between commands.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Troubleshoot common problems
“netstat” is not found
On Linux, the legacy command may not be installed because it is supplied by the net-tools package. First try:
command -v netstat
command -v ssIf ss is available, use sudo ss -ltnup. Otherwise install the distribution’s package that provides netstat, using its normal package manager.
Best Value
- Dual USB-A/C Port Design: This USB hub with ethernet adapter features dual connectors for both USB C and USB A devices, ensuring wide compatibility across laptops, tablets, and smartphones. It includes 1x Gigabit Ethernet port and 3x USB A 3.0 ports, all usable at the same time for smooth and efficient connectivity. 📌Note: When using USB-A to connect devices, please ensure the USB-C is securely attached to the USB-A connector.
- Stable Gigabit Ethernet Adapter: Get fast, wired Internet up to 1000Mbps with this USB C to ethernet adapter. Backward compatible with 10/100Mbps networks for flexible connectivity across various setups. Ideal for streaming, gaming, and large file transfers. 📌Note: Ensure the RJ45 connector is plugged in securely in the port and use CAT6 & above Ethernet cable is required to reach 1 Gbps.
- 5Gbps Data Transfer: Transfer large files, photos, and videos in seconds with this USB 3.0 hub supporting speeds up to 5Gbps—10× faster than USB 2.0. Backward compatible with USB 2.0 and 1.1 devices, this USB splitter expands one port into three for connecting keyboards, mice, and flash drives for everyday use. 📌Note: The three USB-A 3.0 ports share a total 5Gbps bandwidth.【NO HDMI port, NO USB-C data port, and NO PD charging】
- Plug and Play: Reliable USB to ethernet adapter ready to use in seconds. Instantly connects with USB-A and USB-C devices including MacBook Pro/Air, iPad Pro, iMac, Surface Laptops, Chromebook, XPS, tablets, Steam, and smartphones. Works with Windows, macOS, Linux, Chrome OS, and Android. 📌XP/Win7 may need driver. Older systems may not recognize this product due to its USB 3.0 chip. Please refer to the “Installation Manual” to manually download and install the driver.
- Durable & Portable Build: Made with sturdy aluminum alloy, this RJ45 to USB-C adapter delivers long-term durability, efficient heat dissipation, and stable performance for offices, corporate deployments, classrooms, and campus workstations—while its slim, portable form factor makes it ideal for business travel, educators, and mobile professionals.
The process name is missing
Insufficient privileges are the most common cause, especially on Linux. Rerun with sudo; on Windows, try an elevated Command Prompt or use the PID with tasklist. A process may also have exited during collection, or the platform may not expose ownership in that output mode.
The port is listening but connections fail
Check whether the service is bound to 127.0.0.1 or ::1, whether the client is using IPv4 or IPv6, and whether the host firewall allows the traffic. For a different machine or a cloud host, also check router forwarding, security groups, network ACLs, and upstream filtering. A local LISTEN result is not an external connectivity test.
There are many unfamiliar ports
Many legitimate components open sockets, including operating-system services, browsers, development servers, databases, container runtimes, and remote-management tools. Map each unexpected PID to its process, inspect its executable path and publisher, and determine whether it is expected before stopping anything. An unfamiliar port alone does not prove compromise.
Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →A port appears and disappears
The service may be short-lived, activated on demand, restarted by a supervisor, or missed during a single snapshot. Use a refresh command, then compare the PID and process details over time.
Local inventory versus external testing
Use netstat to answer: “What sockets exist on this computer, and which processes own them?” To answer: “Can another machine reach this port?” perform an authorized test from the relevant network, such as a connection attempt or port scan from a second host. The result must be interpreted alongside interface binding, firewall rules, NAT, cloud controls, and network routing.
Only inspect or scan systems you own or are authorized to administer.
Quick Recap
A practical workflow
- List TCP listeners and locally bound UDP sockets for your operating system.
- Record the local address, port, protocol, and PID.
- Map unexpected PIDs to applications or executables.
- Check whether the service is bound to loopback, one interface, or a wildcard address.
- Review host and network firewall rules.
- If external access matters, test from an authorized remote system.
- Investigate unexpected services before disabling or terminating them.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
Recommended Free Tools
