RE: outbound serial modem now times out or drops connection

2008-06-06 Thread Bob McConnell
Mark Stosberg:
 
 We are using qpage to dial a remote TAP modem (Sprint and Verizon), so
 we can send pages about our hosting infrastructure without using the
 internet connection. 
 
 Recently it started failing consistently with timeout to connect.
 I first suspected the remote modem (Sprint), but found I got the same
 result with other carriers. (And Sprint denied a problem on their
end). 
 
 I have since tried a whole battery of approaches including having the
 phone line checked by the local phone company, trying a different
modem
 and trying a different phone cord. 
 
 Trying a new modem (US Robotics external 56k serial modem) did help
 slightly. With it, we consistently connnect, but then after a short
 pause the connection is dropped. This is easily reproduced  in
 minicom: (Using the Sprint TAP modem number here). 
 
   ATDT18886561727
   CONNECT 31200/ARQ/V34/LAPM/V42BIS
   
   NO CARRIER 
 
 I'm out of ideas here. This phone line is only used for this outbound
 service, although our alarm system also uses it for outbound alerts. 
 
 Any suggestions for possible causes or further troubleshooting
 approaches are appreciated. 

Does that modem support Unimodem Diagnostics? What do you get from a
'#UD' command right after the failed connection attempt?

Bob McConnell
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RE: outbound serial modem now times out or drops connection

2008-06-06 Thread Mark Stosberg
 
  Trying a new modem (US Robotics external 56k serial modem) did help
  slightly. With it, we consistently connnect, but then after a short
  pause the connection is dropped. This is easily reproduced  in
  minicom: (Using the Sprint TAP modem number here). 
  
ATDT18886561727
CONNECT 31200/ARQ/V34/LAPM/V42BIS

NO CARRIER 
  
  I'm out of ideas here. This phone line is only used for this outbound
  service, although our alarm system also uses it for outbound alerts. 
  
  Any suggestions for possible causes or further troubleshooting
  approaches are appreciated. 
 
 Does that modem support Unimodem Diagnostics? What do you get from a
 '#UD' command right after the failed connection attempt?

Bob,

Thanks for the response!

I tried that with Minicom, and the prompt just goes back to the hover
over the # sounds and sits there. From some quick Google searches, I
didn't find any mentions of this modem supporting that. 

I'm also not familiar with the details of the TAP protocol. After the
CONNECT, who should speak next? From looking at the qpage source code,
it looks like we might be waiting for ID= to sent from the remote end,
and it is not. 

That would make me suspect the remote end, except that multiple remote
modems are responding the same way. 

   Mark


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RE: outbound serial modem now times out or drops connection

2008-06-06 Thread Bob McConnell
From: Mark Stosberg:
  Trying a new modem (US Robotics external 56k serial modem) did help
  slightly. With it, we consistently connnect, but then after a short
  pause the connection is dropped. This is easily reproduced  in
  minicom: (Using the Sprint TAP modem number here). 
  
ATDT18886561727
CONNECT 31200/ARQ/V34/LAPM/V42BIS

NO CARRIER 
  
  I'm out of ideas here. This phone line is only used for this
outbound
  service, although our alarm system also uses it for outbound
alerts. 
  
  Any suggestions for possible causes or further troubleshooting
  approaches are appreciated. 
 
 Does that modem support Unimodem Diagnostics? What do you get from a
 '#UD' command right after the failed connection attempt?
 
 Bob,
 
 Thanks for the response!
 
 I tried that with Minicom, and the prompt just goes back to the hover
 over the # sounds and sits there. From some quick Google searches, I
 didn't find any mentions of this modem supporting that. 
 
 I'm also not familiar with the details of the TAP protocol. After the
 CONNECT, who should speak next? From looking at the qpage source code,
 it looks like we might be waiting for ID= to sent from the remote
end,
 and it is not. 
 
 That would make me suspect the remote end, except that multiple remote
 modems are responding the same way. 
 
Mark

Mark,

The only tap I am familiar with is /dev/tap virtual Ethernet device, as
I am currently working on a project that makes use of this interface.
Since you get the connect message from your modem, they were able to
negotiate a reliable connection. So you have to assume that you do not
have any phone line issues. Then it becomes a matter of seeing the
correct handshake sequence between the two systems. I would expect the
answering system to start that conversation. The NO CARRIER message
suggests that the other end dropped the connection, or hung up on you
instead of sending the opening message. That should be worth filing a
trouble report.

Is it possible that those serial ports have been disabled, or that
process has been shut down? It is possible the process died without
disabling the auto-answer status of the modem. Some of those modems are
just too smart for their own good.

Please do not CC me on this thread. I can read it just fine from the
list.

Bob McConnell
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