iB::Topic::How do you check a network port is open?

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Topic: How do you check a network port is open?

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Juanito

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Posts: 1601
Joined: Sep. 2005

Posted: Sep. 16 2007,13:48

I'm trying to open up a network port in order to scan over the network. I added the following:

/etc/sources
sane-port 6566/tcp # SANE network scanner daemon

/etc/inetd.conf
sane-port stream tcp nowait dsl.staff /opt/hplip/sbin/saned saned

and then restarted /etc/init.d/inetd. So far things don't seem to be working - is there a way to check that the port is open from the same machine or another machine on the network? By telnet maybe?

roberts

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Posts: 4983
Joined: Oct. 2003

Posted: Sep. 16 2007,14:54

Does
by name:

# netstat -al

by number

# netstat -nl

help?

curaga

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Posts: 2163
Joined: Feb. 2007

Posted: Sep. 16 2007,15:59

You could either try to telnet to that port from another machine, or just do a portscan..

--------------
There's no such thing as life. Those mean little jocks invented it ;)
-
Windows is not a virus. A virus does something!

Juanito

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Posts: 1601
Joined: Sep. 2005

Posted: Sep. 17 2007,15:08

Thanks

Code Sample

$ netstat -at
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 *:bootpc *:* LISTEN
tcp 0 0 *:swat *:* LISTEN
tcp 0 0 *:time *:* LISTEN
tcp 0 0 *:sane *:* LISTEN
tcp 0 0 *:discard *:* LISTEN
tcp 0 0 *:vboxd *:* LISTEN
tcp 0 0 *:daytime *:* LISTEN
tcp 0 0 *:ipp *:* LISTEN

Looks promising.

But:

Code Sample

$ telnet localhost 6566
Trying 127.0.0.1...
Connected to box.
Escape character is '^]'.
Connection closed by foreign host.

albeit from the same machine.

and:

Code Sample

c: telnet \192.168.1.100 6566
...could not open connection to the host, on port 6566: Connect failed

from an xp machine, didn't look so promising.

Maybe this is an issue of user permissions?

curaga

Group: Members
Posts: 2163
Joined: Feb. 2007

Posted: Sep. 17 2007,15:14

..Or a firewall.. But if a port is open, telnetting to it will work, even from XP.
For fun try "telnet google.com 80" and see what happens (if you wanna pretend to be a web browser, type "GET / HTTP/1.0" without the quotes and you'll see google front page get loaded)

--------------
There's no such thing as life. Those mean little jocks invented it ;)
-
Windows is not a virus. A virus does something!

8 replies since Sep. 16 2007,13:48

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Damn Small Linux Board » Damn Small Linux » Networking » How do you check a network port is open?