How to Quickly Detect Occupied Linux Ports with Python

Today I needed a small Python program to probe ports and discovered I didn't know how to check occupied ports on Linux.

How to view occupied ports on Linux

1. lsof -i:<port> – shows which process is using a specific port, e.g., lsof -i:8000.

2. netstat -tunlp | grep <port> – displays the process details for a given port, e.g., netstat -tunlp | grep 8000.

The above commands reveal that port 8000 is occupied by the lightweight file system forwarding service lwfs .

Explanation of the parameters used in the commands is provided in the accompanying image.

Below is a Python script that checks whether a specified IP and port are occupied:

import socket

def is_port_open(ip, port):
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.settimeout(1)
    try:
        s.connect((ip, port))
        return True
    except socket.error:
        return False

if __name__ == "__main__":
    ip = "127.0.0.1"
    port = 8000
    if is_port_open(ip, port):
        print(f"Port {port} on {ip} is occupied")
    else:
        print(f"Port {port} on {ip} is free")

The script’s execution result is shown in the following image.