Re: /etc/services - one service, multiple ports?

[herbert langhans <herbert.raimund%langhans.com.pl@localhost>]

On Tue, May 15, 2012 at 10:16:56AM -0700, Johnny Billquist wrote:
> On 2012-05-15 08.36, herbert langhans wrote:
> >Hi List,
> >I changed the ftp-port in /etc/services to 6021. The simple reason
> >is to avoid password scanning on port 21, it works well.
> >
> >One of the ftp users seems to get handicapped by some firewall or bad
> >ftp-client and cannot log in on port 6021.
> >
> >Is it 'legal' to have multiple ports on one service? This is the current
> >version of /etc/services:
> ><snip>
> >115 ftp-data         20/tcp    # File Transfer [Default Data]
> >116 ftp-data         20/udp    # File Transfer [Default Data]
> >117 ftp              6021/tcp  # File Transfer [Control]
> >118 ftp              6021/udp  # File Transfer [Control]
> >119 ssh              22/tcp  # SSH Remote Login Protocol
> >120 ssh              22/udp  # SSH Remote Login Protocol
> ></snip>
> >
> >I would change it to:
> >115 ftp-data         20/tcp    # File Transfer [Default Data]
> >116 ftp-data         20/udp    # File Transfer [Default Data]
> >     ftp              21/tcp  # File Transfer [Control]
> >     ftp              21/tcp  # File Transfer [Control]
> >118 ftp              6021/udp  # File Transfer [Control]
> >118 ftp              6021/udp  # File Transfer [Control]
> >119 ssh              22/tcp  # SSH Remote Login Protocol
> >120 ssh              22/udp  # SSH Remote Login Protocol
> >
> >Will the ftp-server attach to 21 as well to 6021 (not the same user on
> >both, maybe user A on 21, user B on 6021 simultaneously).
> >
> >I didnt dare to change it yet, dont want to leave the server non
> >bootable or such troubles.
> >
> >Did anybody try such trick?
> >Thanks!
> >herb langhans
> 
> It will work just fine, and exactly as you would expect.
> 
>       Johnny

Thanks Johnny,
I will go for it.
Cheers
herb langhans