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Source: Zifimu
www.cnblogs.com/wangtao1993/p/6144183.html
Today, I want to write a small program in Python to detect whether specific service ports are occupied. I suddenly realized that I didn’t know how to check port usage in Linux. Oh no, I need to learn this quickly. 😁
How to Check Ports in Linux
1. Use lsof -i:port_number to check the usage of a specific port. For example, to check the usage of port 8000, use lsof -i:8000.
# lsof -i:8000
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
lwfs 22065 root 6u IPv4 4395053 0t0 TCP *:irdmi (LISTEN)You can see that port 8000 is already occupied by the lightweight file system forwarding service lwfs.
2. Use netstat -tunlp | grep port_number to check the process status of a specified port. For example, to check the status of port 8000, use netstat -tunlp | grep 8000.
# netstat -tunlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN 4814/rpcbind
tcp 0 0 0.0.0.0:5908 0.0.0.0:* LISTEN 25492/qemu-kvm
tcp 0 0 0.0.0.0:6996 0.0.0.0:* LISTEN 22065/lwfs
tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN 38296/dnsmasq
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 5278/sshd
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 5013/cupsd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 5962/master
tcp 0 0 0.0.0.0:8666 0.0.0.0:* LISTEN 44868/lwfs
tcp 0 0 0.0.0.0:8000 0.0.0.0:* LISTEN 22065/lwfs
# netstat -tunlp | grep 8000
tcp 0 0 0.0.0.0:8000 0.0.0.0:* LISTEN 22065/lwfs Let me explain the meaning of several parameters:
-t (tcp) only shows TCP-related options
-u (udp) only shows UDP-related options
-n refuse to display aliases, convert all displayable numbers to numbers
-l only lists services in the Listen state
-p shows the program name that established the related connectionAdditionally, here is a Python program for monitoring port usage, which can check whether a specified IP’s port is occupied.
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import socket, time, thread
socket.setdefaulttimeout(3) # Set default timeout
def socket_port(ip, port):
"""
Input IP and port number, scan to determine if the port is occupied
"""
try:
if port >=65535:
print u'Port scan finished'
s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
result=s.connect_ex((ip, port))
if result==0:
lock.acquire()
print ip,u':',port,u'port is occupied'
lock.release()
except:
print u'Port scan exception'
def ip_scan(ip):
"""
Input IP, scan the port status of IP from 0 to 65534
"""
try:
print u'Starting scan %s' % ip
start_time=time.time()
for i in range(0,65534):
thread.start_new_thread(socket_port,(ip, int(i)))
print u'Scan completed, total time: %.2f' %(time.time()-start_time)
# raw_input("Press Enter to Exit")
except:
print u'Error scanning IP'
if __name__=='__main__':
url=raw_input('Input the ip you want to scan: ')
lock=thread.allocate_lock()
ip_scan(url) The execution result of this program is as follows:
# python scan_port.py
Input the ip you want to scan: 20.0.208.112
Starting scan 20.0.208.112
20.0.208.112 : 111 port is occupied
20.0.208.112 : 22 port is occupied
20.0.208.112 : 8000 port is occupied
20.0.208.112 : 15996 port is occupied
20.0.208.112 : 41734 port is occupied
Scan completed, total time: 9.38Recommended Reading
(Click the title to jump to read)
How to Discover Hidden Processes and Ports
Comic: The Battle for Port 80
The Story Behind SSH Protocol Port 22
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