linux查看当前服务开放的端口号

netstat -tuln

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN     
tcp6       0      0 :::80                   :::*                    LISTEN     
udp        0      0 0.0.0.0:123             0.0.0.0:*                          

ss -tuln

State      Recv-Q Send-Q        Local Address:Port          Peer Address:Port
LISTEN     0      5                0.0.0.0:22                 0.0.0.0:*     
LISTEN     0      128                       *:80                      *:*       

sudo lsof -i -P -n | grep LISTEN

sshd      1234      root    3u  IPv4  12345      0t0  TCP *:22 (LISTEN)
nginx     5678    www-data    6u  IPv4  23456      0t0  TCP *:80 (LISTEN)

import socket

def check_port(ip, port):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    result = sock.connect_ex((ip, port))
    if result == 0:
        print(f"Port {port} is in use.")
    else:
        print(f"Port {port} is free.")
    sock.close()

check_port('127.0.0.1', 80)