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I want to know the principle of 'port' sensor, how it works

Votes:

0

Let me know how 'port' sensor works. What is a way to check port state? 'netstat' or 'telnet' command?

On what basis will port be checked whether 'open' or 'closed' in TCP session?

For example, When I used the command 'netstat' in cmd for checking 1433 port state as below, PRTG 'port' sensor can check the keyword 'ESTABLISHED' or 'LISTENING' ?

-------------------------------------------------------------------------------------------------

C:\Users\Administrator>netstat -ano|findstr 1433
  TCP    0.0.0.0:1433           0.0.0.0:0              LISTENING       2324
  TCP    127.0.0.1:49212        127.0.0.1:1433         TIME_WAIT       0
  TCP    127.0.0.1:49236        127.0.0.1:1433         TIME_WAIT       0
  TCP    127.0.0.1:49263        127.0.0.1:1433         TIME_WAIT       0
  TCP    127.0.0.1:49288        127.0.0.1:1433         TIME_WAIT       0
  TCP    192.168.0.42:1433      192.168.0.188:58546    ESTABLISHED     2324
  TCP    192.168.0.42:1433      192.168.0.200:59802    ESTABLISHED     2324
  TCP    192.168.0.42:49213     192.168.0.153:1433     TIME_WAIT       0
  TCP    192.168.0.42:49219     192.168.0.153:1433     TIME_WAIT       0
  TCP    192.168.0.42:49237     192.168.0.153:1433     TIME_WAIT       0
  TCP    192.168.0.42:49245     192.168.0.153:1433     TIME_WAIT       0
  TCP    192.168.0.42:49267     192.168.0.153:1433     TIME_WAIT       0
  TCP    192.168.0.42:49271     192.168.0.153:1433     TIME_WAIT       0
  TCP    192.168.0.42:49289     192.168.0.153:1433     TIME_WAIT       0
  TCP    192.168.0.42:49297     192.168.0.153:1433     TIME_WAIT       0
  TCP    [::]:1433              [::]:0                 LISTENING       2324
-------------------------------------------------------------------------------------------------

netstat port sensor telnet

Created on Oct 25, 2019 3:56:33 AM

Last change on Oct 25, 2019 4:22:59 AM by Sven Roggenhofer [Paessler Technical Support]



3 Replies

Votes:

1

Hi,

The Port sensor only uses telnet and the sensor can check if the port is open or closed.
You'll find more information about the Port sensor here.

Kind regards.

Created on Oct 25, 2019 8:14:57 AM by Marijan Horsky [Paessler Support]



Votes:

0

Hi,

Does PRTG run the telnet command directly on the cmd?

(example) > telnet 8.8.8.8 3389

Created on Jan 2, 2020 12:47:46 AM



Votes:

0

Hi Jonathan,

The sensor uses the service and doesn't run it directly in the cmd.

Kind regards.

Created on Jan 2, 2020 8:23:33 AM by Marijan Horsky [Paessler Support]




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