Enquire-link Queries

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Zak Armstrong
New member
Username: Zakarm

Post Number: 1
Registered: 05-2011
Posted on Tuesday, May 10, 2011 - 03:25 pm:   

Hello,

I've had a good scour about to look for this answer but can find anything definitive or anything older than 4-5 year.

I'm using NowSMS as a client when connecting to an SMPP server.

My understanding that the TYPICAL scenario is that the client would enquire link status (Enquire-Link) and expect a response from the server. In addition to this the Server would expect to Receive an Enquire-Link from a client in a slightly larger time-scale.

However I have been presented with the request that our NowSMS client be able to respond to Enquire-Link messages sent from the server. Is this something which this product can support?

I was going to ask the same Question regarding Unbind requests but found the answer here http://support.nowsms.com/discus/messages/1/69893.html

To follow on from this;

From what I have gathered using the product and reading here is that an Enquire-Link is sent (by default) every 58 seconds (From the client to server). I was wondering what the tolerances were with this request (Wait times). Will the product attempt a rebind after a single failure? What is the time out period when awaiting a response from the server? are these values adjustable in using the interface or adding parameters into the INI file?

Many thanks

Zak
Des - NowSMS Support
Board Administrator
Username: Desosms

Post Number: 3162
Registered: 08-2008
Posted on Tuesday, May 10, 2011 - 04:41 pm:   

Hi Zak,

It is unusual for an SMPP server to send enquire_link, but it is perfectly legal. I've seen a few installations where servers do this and that is no problem. NowSMS as a client will acknowledge it.

I believe we have changed behavior for the server initiating an unbind request (where we would send back a generic NAK), to respond and drop the connection. Of course the server is free to drop the connection regardless. I will have to check on the status of that.

I believe the wait for enquire_link timeout is an over generous 60 seconds. The server may have queued other packets in the meantime, and it is possible they may be received before the enquire_link response. The timeout for just the enquire_link response is not adjustable, but there is a setting that applies to all SMPP requests. Failure for any SMPP command other than enquire_link will trigger an enquire_link to test the connection. Failure of enquire_link causes the connection to be dropped. That said, usually if the connection is truly dead at the TCP level, this will be detected without waiting for timeout.

After any failed or dropped connection, NowSMS will automatically initiate a rebind. The RetryInitDelay parameters can be used to adjust the delay here. There are delays inserted based on various operator SMSC policies, as after a failure, an SMSC can become overwhelmed by many clients simultaneously trying to reconnect.

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Des
NowSMS Support
Des - NowSMS Support
Board Administrator
Username: Desosms

Post Number: 3163
Registered: 08-2008
Posted on Tuesday, May 10, 2011 - 04:47 pm:   

Follow-up. I should have read the other thread you referenced, as I would have known it answered the unbind question. Sorry for any confusion!
Zak Armstrong
New member
Username: Zakarm

Post Number: 2
Registered: 05-2011
Posted on Tuesday, May 10, 2011 - 04:50 pm:   

Great stuff! Exactly what I wanted to hear.

Thanks for the hasty response.

Regards

Zak