How to view all active network connections with netstat or ss?
Jun 19, 2025 am 12:48 AMTo view active network connections on Linux, use netstat or ss. 1. Netstat is older and deprecated but still widely used; run sudo netstat -tulnp to show TCP/UDP connections, listening ports, IP addresses, and process info. 2. Ss is faster and recommended; use sudo ss -tulnp for similar output with better performance. 3. Ss supports filtering, like ss -ltnp 'sport = :ssh' for SSH connections only. Both display protocol, local/foreign addresses, port states, and processes when applicable. Use -p selectively to avoid sudo, filter via grep, or use watch for live monitoring.
If you want to see all active network connections on a Linux system, two of the most common tools are netstat
and ss
. While netstat
has been around longer, it's now considered deprecated — but still widely used. The ss
command is faster and more efficient, and it's the recommended alternative in many modern distributions.
Here’s how to use both commands effectively to view active connections.
How to Use netstat
to Show Active Connections
To list all active network connections using netstat
, this basic command covers most needs:
netstat -tulnp
-t
shows TCP connections-u
shows UDP connections-l
lists only listening ports-n
disables DNS lookups (shows IP addresses instead of hostnames)-p
shows the process ID and name (requires root privileges)
You’ll typically run this with sudo
to get full visibility into processes:
sudo netstat -tulnp
This gives you a clear picture of what services are running and which connections are currently open.
How to Use ss
for Faster and More Detailed Output
The ss
command (short for "socket statistics") is designed to be a faster alternative to netstat
.
A good starting point is:
ss -tulnp
The options are similar:
-t
for TCP-u
for UDP-l
for listening sockets-n
to skip hostname resolution-p
to show associated processes
Like with netstat
, you might need sudo
to see all process details:
sudo ss -tulnp
One advantage of ss
is that it can filter results directly on the command line. For example, if you want to see only SSH connections:
ss -ltnp ' sport = :ssh '
Or for HTTP traffic:
ss -ltnp ' sport = :http '
These filters make ss
very powerful when troubleshooting or monitoring specific services.
Interpreting the Output
Both commands will give you a table showing:
- Protocol (TCP/UDP)
- Recv-Q / Send-Q (number of bytes in receive/send queues)
- Local address and port
- Foreign (remote) address and port
- State (like ESTABLISHED, LISTENING)
- Process info (if using
-p
)
Common states you may see:
- LISTEN – service waiting for incoming connections
- ESTABLISHED – active connection
- TIME-WAIT – connection is closing gracefully
If you're scanning for unusual activity, look for unexpected foreign IPs or unknown processes tied to open ports.
Tips for Daily Use
- If you don’t need process info, skip
-p
to avoid needing sudo. - Pipe output to
grep
to narrow down results:ss -tuln | grep ':80'
- Use
-r
withnetstat
to resolve hostnames (but expect slower output). - Combine
watch
with these commands for live monitoring:watch ss -tuln
That’s basically how you check active network connections using
netstat
orss
. Both tools do the job well, butss
is generally faster and more flexible, especially with filtering. Once you get used to the syntax, checking what’s connected becomes second nature.The above is the detailed content of How to view all active network connections with netstat or ss?. For more information, please follow other related articles on the PHP Chinese website!

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