方法1：nmap ip -p port，如nmap 172.17.193.18 -p 5902
根据显示closed/open确定端口是否打开。
若显示：5902/tcp open vnc-2
则表示远程端口已打开。
若显示：5902/tcp closed unknown
则表示远程端口未打开。
方法2：nc -v ip port，如nc -v 172.17.193.18 5902
根据显示的Connected信息确定端口是否打开。
若显示：Ncat:Connected to 172.17.193.18:5902.
则表示远程端口已打开。
若显示：Ncat:Connection refused.
则表示远程端口未打开。
[root@vmi481870 ~]# nmap 62.171.168.* -p 5903 Starting Nmap 7.70 ( https://nmap.org ) at 2020-11-29 14:56 CET Nmap scan report for *.contaboserver.net (62.171.168.*) Host is up (0.00016s latency). PORT STATE SERVICE [v_qing]5903/tcp open vnc-3 //这是打开状态的端口[/v_qing] Nmap done: 1 IP address (1 host up) scanned in 0.28 seconds [root@vmi481870 ~]# nmap 62.171.168.* -p 5904 Starting Nmap 7.70 ( https://nmap.org ) at 2020-11-29 14:57 CET Nmap scan report for *.contaboserver.net (62.171.168.*) Host is up (0.00017s latency). PORT STATE SERVICE [v_qing]5904/tcp closed unknown //这是关闭状态的端口[/v_qing] Nmap done: 1 IP address (1 host up) scanned in 0.29 seconds [root@vmi481870 ~]# nmap 62.171.168.* -p 5905 Starting Nmap 7.70 ( https://nmap.org ) at 2020-11-29 14:57 CET Nmap scan report for *.contaboserver.net (62.171.168.*) Host is up (0.00028s latency). PORT STATE SERVICE [v_qing]5905/tcp closed unknown[/v_qing] Nmap done: 1 IP address (1 host up) scanned in 0.28 seconds
