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20030618: LDM 6.0.13 connections

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  • Subject: 20030618: LDM 6.0.13 connections
  • Date: Wed, 18 Jun 2003 14:57:37 -0600
Hi Daniel,

>Date: Wed, 18 Jun 2003 16:47:19 -0400
>From: "Lemay,Daniel [CMC]" <address@hidden>
>Organization: Environment Canada
>To: "'address@hidden'" <address@hidden>
>Subject: LDM 6.0.13 connections

The above message contained the following:

> I have compiled and installed LDM 6.0.13 on a Linux box. Differents clients
> connect to my box to obtain GEM data.
> 
> Here are the results I obtain with netstat command:
> ============================================================================
> =====
> [ldm@meteo etc]$ netstat -an | grep 388
> tcp        0      0 0.0.0.0:388             0.0.0.0:*               LISTEN
> tcp        1      0 10.10.10.112:388        128.117.13.119:55416
> CLOSE_WAIT
> tcp        1      0 10.10.10.112:388        128.118.28.12:44358
> CLOSE_WAIT
> tcp        0      0 10.10.10.112:388        128.117.13.119:55586
> TIME_WAIT
> tcp        1      0 10.10.10.112:388        128.117.13.119:55328
> CLOSE_WAIT
> tcp        1      0 10.10.10.112:388        128.118.28.12:44405
> CLOSE_WAIT
> tcp        1      0 10.10.10.112:388        128.117.140.27:46064
> CLOSE_WAIT
> tcp        0      0 10.10.10.112:388        128.117.13.119:55539
> ESTABLISHED
> tcp        1      0 10.10.10.112:388        128.118.28.12:44452
> CLOSE_WAIT
> tcp        0      0 10.10.10.112:388        132.208.133.165:24762
> ESTABLISHED
> tcp        1      0 10.10.10.112:388        128.117.140.27:45899
> CLOSE_WAIT
> tcp        0      0 10.10.10.112:388        128.118.28.12:44491
> ESTABLISHED
> tcp        0      0 10.10.10.112:388        128.118.28.12:44517
> TIME_WAIT
> tcp        1      0 10.10.10.112:388        132.208.133.165:24709
> CLOSE_WAIT
> tcp        1      0 10.10.10.112:388        128.117.140.27:45935
> CLOSE_WAIT
> 
> It seems that there is no persistence in the connection that a client
> establish. Is it normal?

There should be some persistance.  The upstream LDM process and the
downstream LDM process should hang around for as long as the connection
is good.

I note from the LDM logfile on shemp.unidata.ucar.edu that a
lot of connection attempts are refused:

ldmd.log.1:Jun 18 20:31:44 shemp.unidata.ucar.edu ldm[3703]: Couldn't connect 
to upstream LDM on ldm.meteo.ec.gc.ca: RPC: Remote system error - Connection 
refused

Does your machine have a log entry for this (UTC) time?


> Some clients seem to have more than one connection (CMC offers only GEM
> Data, not any other type of fee). For example, 128.118.28.12 has 3
> CLOSE_WAIT, 1 ESTABLISHED and 1 TIME_WAIT entries. Is it normal?

I'm not sure about the TIME_WAIT, but if a downstream LDM hasn't
received anything from the upstream LDM in one minute, then it will try
to connect to the top-level, upstream LDM to ask it if the sending LDM
has died.  This might be the cause of the CLOSE_WAIT connection.  This
might also be the cause of the refused connections described above.

> Thanks in advance
> 
> Daniel Lemay
> 
> ===============================================
> email: address@hidden
> phone: (514) 421-7274
> ===============================================
> Services d'acquisition et de distribution des données
> Centre Météorologique Canadien - Environnement Canada
> ===============================================
> Data Acquisition and Distribution Services (DADS)
> Canadian Meteorological Center - Environment Canada
> ===============================================

Regards,
Steve Emmerson