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[Solved] Unknown ports

Linux Kernel, Network, and Services configuration.
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sakurita
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[Solved] Unknown ports

#1 Post by sakurita »

Hey there;

I was performing routine port check:

Code: Select all

Netid  State   Recv-Q  Send-Q   Local Address:Port    Peer Address:Port Process 
udp    UNCONN  0       0              0.0.0.0:51820        0.0.0.0:*            
udp    UNCONN  0       0              0.0.0.0:631          0.0.0.0:*            
udp    UNCONN  0       0              0.0.0.0:5353         0.0.0.0:*            
udp    UNCONN  0       0              0.0.0.0:40175        0.0.0.0:*            
udp    UNCONN  0       0                 [::]:51820           [::]:*            
udp    UNCONN  0       0                 [::]:60038           [::]:*            
udp    UNCONN  0       0                 [::]:5353            [::]:*            
tcp    LISTEN  0       128          127.0.0.1:631          0.0.0.0:*            

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Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN     
udp        0      0 0.0.0.0:51232           0.0.0.0:*                          
udp        0      0 0.0.0.0:51820           0.0.0.0:*                          
udp        0      0 0.0.0.0:631             0.0.0.0:*                          
udp        0      0 0.0.0.0:5353            0.0.0.0:*                          
udp        0      0 0.0.0.0:40175           0.0.0.0:*                          
udp6       0      0 :::51820                :::*                               
udp6       0      0 :::60038                :::*                               
udp6       0      0 :::5353                 :::*                               
I tried to identify (using google) the app o daemon associate with some ports, but others it's imposible to said what applications is behind.
it is possible to find out the application or process that opens those ports?

I'm using a firewall to denied incoming connections.
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Debian Ports.png
Last edited by sakurita on 2023-03-31 10:50, edited 1 time in total.

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Re: [Software] Unknown ports

#2 Post by Aki »

Hello,
sakurita wrote: 2023-03-16 17:46 it is possible to find out the application or process that opens those ports?
You can use the following command from net-tools package:

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netstat -tcup
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Re: [Software] Unknown ports

#3 Post by kent_dorfman766 »

sudo lsof -i also shows bound network ports and the daemon that owns them.

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Re: [Software] Unknown ports

#4 Post by Aki »

@sakurita: hello, can you update the thread ?
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Re: [Software] Unknown ports (solved)

#5 Post by sakurita »

Aki wrote: 2023-03-22 08:08 @sakurita: hello, can you update the thread ?
Done

Thanks

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Re: [Solved] Unknown ports

#6 Post by Aki »

@sakurita: have you identified the programs that opened the “unknown ports” ? Were commands suggested in previous posts useful to you ?
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Re: [Solved] Unknown ports

#7 Post by kent_dorfman766 »

FWIW, "sudo lsof -i" is an alternate way of seeing who is bound to a network socket.

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Re: [Solved] Unknown ports

#8 Post by sakurita »

Aki wrote: 2023-03-31 11:50 @sakurita: have you identified the programs that opened the “unknown ports” ? Were commands suggested in previous posts useful to you ?
For this ports:

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udp        0      0 0.0.0.0:51820           0.0.0.0:*                           -                    off (0.00/0/0)
udp        0      0 0.0.0.0:631             0.0.0.0:*                           -                    off (0.00/0/0)
udp        0      0 0.0.0.0:42088           0.0.0.0:*                           -                    off (0.00/0/0)
udp        0      0 0.0.0.0:5353            0.0.0.0:*                           -                    off (0.00/0/0)
Using "sudo lsof -i":

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avahi-dae  577 avahi   12u  IPv4  13289      0t0  UDP *:mdns 
avahi-dae  577 avahi   13u  IPv6  13290      0t0  UDP *:mdns 
avahi-dae  577 avahi   14u  IPv4  13291      0t0  UDP *:42088 
avahi-dae  577 avahi   15u  IPv6  13292      0t0  UDP *:52042 
cups-brow  706  root    7u  IPv4  19707      0t0  UDP *:631
As you see, not all of them are resolved :( 5353 is multicast but i didn't got an PID, same with 51820 .......
Using "netstat -tcup" got less PID

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Re: [Solved] Unknown ports

#9 Post by kent_dorfman766 »

FWIW, I see nothing alarming about the above.

They are resolved as avahi-daemon owned. Don't expect those high number UDP binds to be persistent. They will change...frequently

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Re: [Solved] Unknown ports

#10 Post by sakurita »

Finally ...... UDP 51820 is wireguard connection related.

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