NMap，也就是Network Mapper，最早是Linux下的網路掃描和嗅探工具包。

1 安裝

apt-get install nmap

2 使用,檢視ip下所有對外的埠

$ sudo nmap -sS ip

Starting Nmap 7.01 ( https://nmap.org ) at 2018-11-16 18:29 CST
Nmap scan report for ip
Host is up (0.038s latency).
Not shown: 997 filtered ports
PORT     STATE  SERVICE
22/tcp   open   ssh
80/tcp   open   http
3389/tcp closed ms-wbt-server

Nmap done: 1 IP address (1 host up) scanned in 31.47 seconds
 

可以看到 22埠，80埠，3389埠對外開放了。
可以看到狀態是開啟還是關閉的。
可以看到對應的服務是什麼型別的。

也可以檢視具體的埠是否對外開放。

 nmap ip -p80

Starting Nmap 7.01 ( https://nmap.org ) at 2018-11-16 18:34 CST
Nmap scan report for ip
Host is up (0.036s latency).
PORT   STATE SERVICE
80/tcp open  http

Nmap done: 1 IP address (1 host up) scanned in 0.12 seconds
 

$ nmap ip -p 80

Starting Nmap 7.01 ( https://nmap.org ) at 2018-11-16 18:35 CST
Nmap scan report for ip
Host is up (0.036s latency).
PORT   STATE SERVICE
80/tcp open  http

Nmap done: 1 IP address (1 host up) scanned in 0.11 seconds

還可以查範圍的。

$ nmap 39.106.106.11 -p 80-4000

Starting Nmap 7.01 ( https://nmap.org ) at 2018-11-16 18:36 CST
Nmap scan report for 39.106.106.11
Host is up (0.038s latency).
Not shown: 3919 filtered ports
PORT     STATE  SERVICE
80/tcp   open   http
3389/tcp closed ms-wbt-server

Nmap done: 1 IP address (1 host up) scanned in 11.74 seconds
 

基本可以替代了 telnet

$ telnet ip port
Trying ip...
Connected to ip...