Linux – Ping TCP port?

通常我們會用 ping 這個指令來確認對方主機的狀態,但是要確定對方主機某一個埠 TCP port 是否有開啟,那還是一樣可以用 ping 的嗎?? 答案是不行的因為 Ping 使用了 ICMP ( Internet Control Message Protocol)

ICMP 的全名是 Internet Control Message Protocol, ICMP 主要是一個 錯誤偵測與回報機制的協定,而 ICMP 跟 IP 一樣在 TCP/IP 7 layer 的第三層 網路層 (Network) .而 TCP 是 IP 的上一層,才有 Port 埠的定義.所以我們無法透過 ICMP 得知,某 TCP Port 是否開啟.

那有其他方式嗎?? 有的,下面幾種方式.

Windows:

• PaPing:http://code.google.com/p/paping

  C:\Users\Ben\Desktop>paping www.google.com -p 80 -c 4
  paping v1.5.5 - Copyright (c) 2011 Mike Lovell
  
  Connecting to www.google.com on TCP 80:
  
  Connected to 173.194.72.103: time=165.52ms protocol=TCP port=80
  Connected to 173.194.72.103: time=213.53ms protocol=TCP port=80
  Connected to 173.194.72.103: time=71.51ms protocol=TCP port=80
  Connected to 173.194.72.103: time=139.52ms protocol=TCP port=80
  
  Connection statistics:
          Attempted = 4, Connected = 4, Failed = 0 (0.00%)
  Approximate connection times:
          Minimum = 71.51ms, Maximum = 213.53ms, Average = 147.52ms
  

Linux:

• PaPing:http://code.google.com/p/paping

  #paping www.google.com -p 80 -c 4

• nc (或是 netcat)

  #nc -vz google.com 80

• hping

  #hping google.com -S -V -p 80

• nmap

  #nmap -p 80 google.com

  其他參數使用請參考 https://benjr.tw/28087

• Telnet
  不過最奇特的是可以使用 telnet 來試驗.

  benteki-air:~ ben$ telnet www.google.com 23
  Trying 74.125.203.99...
  ^C
  

  沒開 port 23 (telnet)

  benteki-air:~ ben$ telnet www.google.com 80
  Trying 74.125.23.147...
  Connected to www.google.com.
  Escape character is '^]'.
  ^C^C^]
  telnet> quit
  Connection closed.
  benteki-air:~ ben$ telnet www.google.com 443
  Trying 74.125.23.103...
  Connected to www.google.com.
  Escape character is '^]'.
  ^]
  

  TCP Port 80(HTTP),443(HTTPS) 都有開.