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Telnet in Linux

Connect to remote host / Check the port availability.

Some of commands while using telnet:

  • # netstat -tulpn 
    • This commands shows which ports are used in this system 
  • # telnet localhost 80 
    • If this command throws an error like connection refused then the port 80 is not in use. We can use this port. 
    • If this command throws an error like connected then the port is in use. We cannot use this port/li>
    • Telnet is used to check whether a particular port is used or not. To exit from telnet command press ctrl + j

Default Ports:

Port Number

Service

21

FTP (File Transfer protocol)

22

SSH (Secure Shell)

23

Telnet

25

SMTP (Simple Mail Transfer Protocol)

53

DNS (Domain Name Server)

80

http (Hypertext Transfer Protocol)

443

https (Hypertext Transfer Protocol Secure)

 

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