How to handle TCP retransmission

Hi,

I am developing a sms application using jsmpp api, once i crate a connection with the smsc my application is sending keep-alive messages every 30 seconds. During this process sometimes tcp retransmission is happening. So which means smsc getting two keep-alives before it sends back the ack for the first keep-alive which makes to throw negative response exception. Our smsc is not allowed for multiple connections.

I monitor this scenario using wireshark with running ozeki sms gateway. At that time tcp retranmission also happened. But any way I think that ozeki have managed to control the retransmission without disconnecting the connection. But i don't have any idea how to handle this retransmission.

Have someone experienced this kind of issue. Please help me to rectify this matter.


Thanks in advanced,
Uthpala

Isn't TCP retransmission supposed to be transparent to applications? In other words, shouldn't the receiving end silently ignore the duplicate messages at a level below smsc?

Depending on the platform, you might be able to fiddle with the retransmission timeout on the sending side.

Hi .. Do you know a better method to listen to retransmissions. If so please be kind enough to share with me. Because in my app i don't have a method to listen to ack from smsc side. Still I couldn't find a way. Can we do this creating a socket connection ?

Uthpala

As an application programmer, I've never had a reason to know or care what the TCP layer is doing. I only know it's supposed to be transparent. The fact that retransmission affects your apps in any way suggests there's a bug in your platform's TCP layer.

I also think this should be transparent, but when i used ozeki sms gateway to check the connectivity it works fine even though retransmission is happening. So in my opinion i think i have to handle this scenario from app side. But unfortunately i don't have any idea how to do this.

You can monitor and capture every packet through Jpcap libraries. Follow this..Jpcap - a Java library for capturing and sending network packets