Identify Processes Listening on Specific Ports

Identify Processes Listening on Specific Ports | Generated by AI

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Question: How do I find out which process or application is listening on port 18789?

Answer:

How to Find Which Process Is Listening on Port 18789

Replace 18789 in each command below with any port number you want to check.

🐧 Linux / macOS

Method 1: `ss` (Recommended — Modern)

ss is the recommended modern tool to find which process is listening on a specific port.

sudo ss --listening --numeric --processes sport :18789

Short form:

sudo ss -lntp sport :18789

Sample output:

Netid  State   Recv-Q  Send-Q  Local Address:Port  Peer Address:Port  Process
tcp    LISTEN  0       128     0.0.0.0:18789        0.0.0.0:*          users:(("myapp",pid=12345,fd=7))

Method 2: `lsof`

lsof lists all open files in a Linux system; since network ports are treated as files, you can use it with -i :port_number to find the process using that port.

sudo lsof -i :18789

Sample output:

COMMAND   PID   USER   FD   TYPE  DEVICE  SIZE/OFF  NODE  NAME
myapp   12345   root    3u  IPv4   19373       0t0   TCP   *:18789 (LISTEN)

The output shows the process name, PID, owner user, and file descriptor.

Method 3: `netstat`

netstat is the traditional tool for displaying network connections and is still widely used.

sudo netstat -tulpn | grep :18789

Options explained:

Option	Meaning
`-t`	TCP connections
`-u`	UDP connections
`-l`	Listening sockets only
`-p`	Show PID/program name
`-n`	Show numeric ports (no DNS resolution)

Note: netstat may not be installed by default on newer distros. Install with: sudo apt install net-tools

Method 4: `fuser`

sudo fuser -v 18789/tcp

Sample output:

                     USER        PID ACCESS COMMAND
18789/tcp:           root      12345 F....  myapp

🪟 Windows

Method 1: `netstat` in Command Prompt (Run as Administrator)

netstat -ano | findstr :18789

Sample output:

TCP    0.0.0.0:18789    0.0.0.0:0    LISTENING    12345

The last number is the PID. Then find the process name:

tasklist /FI "PID eq 12345"

Method 2: PowerShell (One-liner)

Get-Process -Id (Get-NetTCPConnection -LocalPort 18789).OwningProcess

This directly outputs the process name without needing to look up the PID separately.

Quick Reference Summary

OS	Command
Linux (modern)	`sudo ss -lntp sport :18789`
Linux (lsof)	`sudo lsof -i :18789`
Linux (netstat)	`sudo netstat -tulpn \\| grep :18789`
Windows CMD	`netstat -ano \\| findstr :18789`
Windows PowerShell	`Get-NetTCPConnection -LocalPort 18789`

💡 If nothing is returned, it means no process is currently listening on port 18789.

References:

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