Re: Available port numbers

[Jim Langston <jimlangston@xxxxxxxxxxxxxxxx>]

Do you want to know what the *standard* port numbers are?

In Windows open up the file C:\WINDOWS\SERVICES in any text editor.  These
list the standard port numbers for various applications.  In Windows NT it
is under C:\WINNT\SYSTEM32\drivers\etc\services

When looking for a free port for your own application, don't pick one that
is a standard for something else.

Don't pick 12345 or 37337 either, as those are used by popular trojan back
door programs.

I don't believe the same type of file exists on the AS/400, but I may be
mistaken.

Regards,

Jim Langston

I thought I was wrong once, but I was mistaken.


Andrew.Lutz@abbott.com wrote:
> 
> Simon,
> 
> Thanks for the additional tip with regards to using WRKSRVTBLE in addition to
> NETSTAT,  it would appear that neither tool provides a complete picture
> though.....
> 
> My understanding is that you should start looking for port assignments above
> 1024 any recommendations?
> 
> Andrew
> 
> 
>                     "Simon Coulter"
>                     <shc@flybynight        To:     WEB400@midrange.com
>                     .com.au>               cc:
>                     Sent by:               Subject:     Re: Available port 
>numbers
>                     owner-web400@mi
>                     drange.com
> 
> 
>                     05/17/2001
>                     11:51 PM
>                     Please respond
>                     to WEB400
> 
> 
> 
> M
> Hello Lucille,
> 
> You wrote:
> >I need to find an available port number on the AS400 to specify on my
> >instance of the server.  At present, there does not appear to be any AS400
> >command that will list available port numbers or numbers that have been
> >taken up.  Does anyone know of a simple way of finding out this information?
> 
> You need to examine the contents of the services file.  Run the command CFGTCP
> 
> and take option 21 and then option 1 (or just run the WRKSRVTBLE command).
> The
> resulting list is the list of assigned ports.  Not all of them will be active
> on
> your system but you should not use any of the assigned ports unless you have a
> 
> very good reason for so doing.
> 
> Pick a port number that is not in the list and use that for your application.
> 
> If your application is written properly it should be telling you to add an
> entry
> in the services table and the application will use the port associated with
> the
> entry.
> 
> It is not sufficient to use NETSTAT to determine available ports because that
> lists only the active ports not the assigned ones.
> 
> Regards,
> Simon Coulter.
> 
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