Telnet service connections between hosts of different systems

Source: Internet
Author: User
Tags nmap port scan

How do we operate the Telnet service on different host systems? Today, we will explain the remote connection between the XP system and the Linux system. Now let's take a look at the following content. Host operating system: XP, virtual machine operating system: CentOS, bridging.

1. linux telnet Service:

  1. # Telnet localhost or
  2. Trying
  3. Telnet: connect to address Connection refused
  4. Telnet: Unable to connect to remote host: Connection refused

2. telnet service from xp to linux:

  1. C:> telnet
  2. Connecting to the connection to the host cannot be opened. port 23: Connection Failed
  3. # Chkconfig -- list | grep telnet
  4. Krb5-telnet: Off

Indicates that only the Kerberos server is installed, which is also a type of telnet, but not started.

From the above command can be seen that telnet is not installed and the krb5-telnet (also provides a telnet Service) is not started? Why? By default, the telnet service is not installed in linux, because the clear code is transmitted via telnet, which is too insecure and telnet is very old .. it is basically useless. We recommend that you use ssh to encrypt the transmitted information, which is much safer and better. Therefore, do not use telnet. Forget it. if you have to use it for a while, let's take a look. telnet may be used when the host and target board are connected in the embedded system. In short, ssh is used instead of telnet)

Because telnet is not installed, the corresponding items cannot be found with chkconfig and ntsysv, but the krb5-telnet is installed by default, note: ntsysv is dedicated to the Red Hat series, not the standard command. telnet uses port 23. in linux, run the following command to check the port status: nmap port scan and netstat-lt network service listen.

  1. #nmap localhost  
  3. 22/tcp  open  ssh  
  4. 23/tcp  open  telnet  
  5. 25/tcp  open  smtp  
  6. 111/tcp open  rpcbind  
  7. 631/tcp open  ipp  
  8. 809/tcp open  unknown  
  9. # netstat -lt  
  10. Proto Recv-Q Send-Q Local Address               Foreign Address             State  
  11. tcp        0      0 *:809                       *:*                         LISTEN  
  12. tcp        0      0 *:sunrpc                    *:*                         LISTEN  
  13. tcp        0      0 *:telnet                    *:*                         LISTEN  
  14. tcp        0      0 localhost.localdomain:ipp   *:*                         LISTEN  
  15. tcp        0      0 localhost.localdomain:smtp  *:*                         LISTEN  
  16. tcp        0      0 *:ssh                       *:*                         LISTEN 

The telnet service is not installed, so no corresponding items exist. run rpm-qa | grep telnet to check whether the installation is successful. telnet-clinet is installed by default. telnet is usually used. telnet-server is used for the server. use yum install telnet-server for installation, and then configure accordingly.

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