How to check ports in Linux

How to check the port in Linux

1, lsof -i: The port number is used Check the usage of a certain port, for example, check the usage of port 8000, 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 has been occupied by the lightweight file system forwarding service lwfs

2, netstat -tunlp |grep Port number, used to check the process status of the specified port number, such as checking the status of port 8000, 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

Explain the meaning of several parameters:

 -t (tcp) 仅显示tcp相关选项
                                 -u (udp)仅显示udp相关选项
                                 -n 拒绝显示别名，能显示数字的全部转化为数字
                                 -l 仅列出在Listen(监听)的服务状态
                                 -p 显示建立相关链接的程序名

Attach a python port occupancy monitoring program, which can monitor whether the port of the specified IP is occupied.

#!/usr/bin/env python
  # -*- coding:utf-8 -*-
  
  import socket, time, thread
  socket.setdefaulttimeout(3) #设置默认超时时间
  
  def socket_port(ip, port):
  """
  输入IP和端口号，扫描判断端口是否占用
 """
 try:
 if port >=65535:
 print u'端口扫描结束'
 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'端口已占用'
 lock.release()
 except:
 print u'端口扫描异常'
 
 def ip_scan(ip):
      """
      输入IP，扫描IP的0-65534端口情况
      """
      try:
          print u'开始扫描 %s' % ip
          start_time=time.time()
          for i in range(0,65534):
              thread.start_new_thread(socket_port,(ip, int(i)))
          print u'扫描端口完成，总共用时：%.2f' %(time.time()-start_time)
  #       raw_input("Press Enter to Exit")
      except:
          print u'扫描ip出错'
  
  if __name__=='__main__':
      url=raw_input('Input the ip you want to scan: ')
      lock=thread.allocate_lock()
      ip_scan(url)

The execution results of this program are as follows:

# python scan_port.py
Input the ip you want to scan: 20.0.208.112
开始扫描 20.0.208.112
20.0.208.112 : 111 端口已占用
20.0.208.112 : 22 端口已占用
20.0.208.112 : 8000 端口已占用
20.0.208.112 : 15996 端口已占用
20.0.208.112 : 41734 端口已占用
扫描端口完成，总共用时：9.38

Recommended related Linux video tutorials: "Linux Tutorial"

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