Common mode telnet ip port (e.g., Telnet 5902 172.17.193.18 ) Test remote host port is open, or for testing the current environment and a firewall between the remote host port opened or not.
telnet
[Oldboy the root @ ~] # 80 Telnet Baidu.com
the Trying 123.125.114.144 ...
Connected to Baidu.com (123.125.114.144). # ==> Connected expressed communication occurs, indicating the port 80 open Baidu
Escape character is '^]'. # ==> ctrl +] quit here.
^]
The Telnet> quit
Connection Closed.
In addition to telnet, you can also use:
Method. 1: nmap -p IP Port , such as nmap 172.17.193.18 -p 5902
The display closed / open port is open is determined.
If it displays: 5902 / tcp open vnc-2
It means that the remote port is open.
If the display: 5902 / tcp closed unknown
It means that the remote port is not open.
Method 2: nc -v ip port, such as nc -v 172.17.193.18 5902
Connected ports are open determined according to the information displayed.
If the display: Ncat: Connected to 172.17.193.18:5902.
It means that the remote port is open.
If the display: Ncat: Connection refused.
It means that the remote port is not open.