Re: Using telnet with USS

OK so there’s a single instance of inetd running in an address space in z/OS. But the fact of the matter is that there are two services files, one in USS and the other in z/OS, so I wonder which one is used for telnetting to USS. I found a note in one of the manuals that says that you should choose different ports for USS and z/OS telnet, but that doesn’t seem to make a difference. In addition the TCP/IP profile in zOS lists the ports and what apps service them:

    20 TCP OMVS      NOAUTOLOG ; FTP Server
    21 TCP OMVS                ; FTP Server
    23 TCP TN3270              ; Telnet Server
    25 TCP SMTP                ; SMTP Server
    53 TCP NAMESRV             ; Domain Name Server
    53 UDP NAMESRV             ; Domain Name Server
    69 UDP OMVS                ; OE TFTP SERVER
    80 TCP OMVS                ; OE WEB SERVER
…
   1021 TCP OMVS                ; OE FTP SERVER
   1023 TCP OMVS                ; OE TELNET SERVER
   1023 UDP OMVS                ; OE TELNET SERVER
   1024 TCP OMVS                ; OE SERVICES


Note that the ports from 1021 through 1024 are (I think) supposed to be serviced by OMVS, but I don’t know if that means that a request for port 1023 for example is passed through to USS.

What I’m really looking for is a cogent explanation of how all this fits together. I’ve done a fair amount of reading, but I haven’t found anything yet.

I must admit that I haven’t played much with netstat in TSO because I find TSO a bit of a pain to use; I prefer to use tsobatch so I can submit jobs from my Unix env and look at the results in a decent editor (emacs). I will try though to play with it the next time I IPL.

Thanks for your interest.

John Murray

Ottawa

> On 16 Sep 2019, at 17:51, Jon Perryman jperryma-yBeKhBN/[email protected] [H390-MVS] <[email protected]> wrote:
> 
> 
> I hope you got telnet working.
> 
> As for INETD, there is only a single instance running in MVS Unix. What you see in MVS is the MVS address space (dubbed) where it is running. Cancel this address space would terminate the INETD process.
> 
> As for the services file, stop thinking singular like in Unix and think combined. Unix admins have a different skillset than z/OS sysprogs. They want to use vi instead of ISPF edit. Additionally, remember that z/OS does not require a file system, so /etc may not exist but TCP still requires the /etc/services definitions.
> 
> As I said before, debug this as if it were a Unix system. Use netstat and verify the port is listen by the INETD process. Look at unix logs for error messages. Instead of specifying the service name in inetd conf, specify the port number.  Look as MVS syslog to see if there are messages there.. 
> 
> Jon
> 
> 
> On Monday, September 9, 2019, 07:42:28 AM PDT, John Murray [email protected] <mailto:[email protected]> [H390-MVS] <[email protected] <mailto:[email protected]>> wrote:
> 
> 
>  
> There are two instances of inetd, one in USS and one in z/OS. The USS one uses the /etc/services file to determine which ports are associated with which applications and the z/OS uses some ETC.SERVICES dataset to do the same. So my question is: how does z/OS determine which ETC.SERVICES dataset to use?
> 
> 
> The reason I ask the question is because I cannot get telnet to contact USS. I know it’s because I have to use different ports for telnet on USS and z/OS which I believe I’ve done, but it doesn’t work. My theory is that I’ve update the wrong ETC.SERVICES dataset.
> 
> John Murray
> 
> Ottawa
> 
>> On 8 Sep 2019, at 16:38, [email protected] <mailto:[email protected]> [H390-MVS] <[email protected] <mailto:[email protected]>> wrote:
>> 
>> Do you mean /etc/services from Unix file system? It's not a dataset. And it does not define what is started and what not.
>> 
> 
> 
>